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State of Florida Department of Environmental Protection David B. Struhs, Secretary
Division of Administrative and Technical Services
Florida Geological Survey Walter Schmidt, State Geologist and Chief
Forse v"eY ..
Seasonal Variation in Sand Beach Sh e Position and Beach Width
mslB alsilie and
Open-Ocean Water Level Datum Planes Use and Misuse in Coastal Applications by
" ii~~~~~~~iii~~~~............ ..... ......by .... ,,i :.H .: .. :,
James H. Balsillie
Published for the Florida Geological Survey Tallahassee, Florida 1999







LETTER OF TRANSMITTAL
C5OLO GI
Florida Geological Survey Tallahassee
Governor Jeb Bush
Florida Department of Environmental Protection Tallahassee, Florida 32304-7700
Dear Governor Bush:
The Florida Geological Survey, Division of Administrative and Technical Services, Department of Environmental Protection is publishing two papers: "Seasonal variation in sandy beach shoreline position and beach width" and "Open-ocean water level datum planes: Use and misuse in coastal applications".
The first paper identifies a methodology for predicting seasonal shifts in Florida's shorelines. A number of practical uses emerge from the research, two of which are the analytical assessment of long-term shoreline erosion data, and determination of the seaward boundary of public versus private ownership.
The second paper is a companion paper to "Open-ocean water datum planes for monumented coasts of Florida" published by the Florida Geological Survey as a separate work. It identifies erroneous applications made when considering mean sea level (MSL), mean high water (MHW), mean low water (MLW), etc., tidal datum planes, illustrating why they are erroneous using practical examples, and details how proper applications should be determined.
Respectfully yours,
Walter Schmidt, Ph.D., P.G. State Geologist and Chief Florida Geological Survey
Hi







CONTENTS
Page
SEASONAL VARIATION IN SANDY BEACH SHORELINE POSITION AND BEACH WIDTH
A BSTRA CT .......................................................... 1
INTR O DUCTIO N ........................................................ 1
SEASONAL VARIABILITY ............................................... 2
DATA AND RESULTS .................................................. 3
Data ........................................................ 3
Results ...................................................... 7
DISCUSSION ........................................................ 9
The Single Extreme Event and the Combined Storm Season ............... 9
Beach Sedim ents ............................................... 11
Astronom ical Tides .............................................. 14
APPLICATION OF RESULTS ............................................ 15
General Knowledge ............................................. 16
Seaward Boundary of Public versus Private Ownership .................. 16
Long-Term Shoreline Changes .................................... 17
Project Design and Performance Assessment ......................... 19
CONCLUDING REMARKS ............................................20
ACKNOW LEDGEMENTS ............................................. 20
REFERENCES .....................................................20
LIST OF FIGURES
Figure 1. Relationship between seasonal shoreline variability, V., and mean range
of tide,h . .. .............. .... ................ ... .. .......4
Figure 2. Monthly time series for Torrey Pines Beach, California, for shoreline
variability, V; breaker height, Hb, and wave period, T ..................... 5
Figure 3. Monthly time series for Stinson Beach, California, for shoreline variability,
V; breaker height, Hb, and wave period, T. ............................. 5
Figure 4. Monthly time series for Jupiter Beach, Rlorida, for shoreline variability, V;
breaker height, Hb, and wave period, T. ............................... 6
Figure 5. Monthly time series for Gleneden Beach, Oregon, for shoreline variability,
V; breaker height, Hb, and wave period, T. ............................ 6
Figure 6. Illustration of mathematical fit for equation (1) ...................... 9
Figure 7. Illustration of mathematical fit for equation (2) ...................... 9
Figure 8. Example of the quick response and recovery of the beach to storm wave
activity, Pensacola Beach, Florida, December 1974 .................... 10
Figure 9. Monthly average occurrences of extreme event wave events for the Outer
Banks of North Carolina ......................................... 11
V




Figure 10. Typical examples of time series relation of monthly data for breaker
height, wave period, and foreshore slope grain size for California and
northwestern Florida panhandle .................................. 13
Figure 11. Monthly variation in sea level for the contiguous United States. .......... 16
Figure 12. Example of long-term shoreline change rate temporal analysis using
seasonal shoreline shift data .................................... 18
LIST OF TABLES
Table 1. Force, response, and property elements for seasonal shoreline shift analysis. . 4 Table 2. Assessment of the wave steepness ratio for a selection of expressions
related to VS. --...-....*..................................... 8
Table 3. Mean annual beach grain size (foreshore slope samples) from monthly
data, and range in size ........................................ 12
Table 4. Two cases of sedimentologic response of moment measures to wave
energy levels ............................................... 12
Table 5. Seasonal range in monthly average water levels...................... 15
APPENDIX
APPENDIX: PROPAGATION OF ERRORS IN COMPUTING .................... 28
OPEN-OCEAN WATER LEVEL DATUM PLANES: USE AND MISUSE IN COASTAL APPLICATIONS
A BSTRA CT ...................................................... 29
INTRO DUCTIO N ................................................... 29
INLETS/OUTLETS AND THE ASTRONOMICAL TIDE ........... ............... 33
WATER LEVEL DATUM PLANES ....................................... 33
SYNERGISTIC TIDAL DATUM PLANE APPLICATIONS ........................ 36
EXTREME EVENT IMPACT ...................................... 36
LONGER-TERM BEACH RESPONSES ...............................37
SeasonalBeach Changes ..................................41
Long-Term Beach Changes .................................42
THE SURF BASE .............................................43
SEA LEVEL RISE .............................................47
MONERGISTIC TIDAL DATUM PLANE APPLICATIONS ........................ 48
DESIGN SOFFIT ELEVATION CALCULATIONS ......................... 48
EROSION DEPTH/SCOUR CALCULATIONS ........................... 49
SEASONAL HIGH WATER CALCULATIONS ,.......................... 49
BEACH-COAST NICKPOINT ELEVATION ............................. 50
BOUNDARY OF PUBLIC VERSUS PRIVATE PROPERTY OWNERSHIP ......... 50 INLETS AND ASSOCIATED ASTRONOMICAL TIDES ......................... 52
CO NCLUSIONS ................................................... 54
ACKNOW LEDGEMENTS ............................................. 54
REFEREN CES ..................................................... 54
vi




LIST OF FIGURES
Figure 1. Relationship between open coast tidal datums and National Geodetic
Vertical Datum for the Florida East Coast ............................. 31
Figure 2. Relationship between open coast tidal datums and National Geodetic
Vertical Datum for the Florida Lower Gulf Coast ........................ 32
Figure 3. Relationship between open coast tidal datums and National Geodetic
Vertical Datum for the Northwest Panhandle Gulf Coast of Florida .......... 32 Figure 4. Erosion volumes, Qe, above MHW for identical profiles impacted by
identical storm events, but with different local MHW planes ............... 37
Figure 5. Beach profile-related terms..................................... 39
Figure 6. Seasonal horizontal shoreline shift analysis ........................ 41
Figure 7. Long-term shoreline shift analysis ............................... 43
Figure 8. Semidiurnal tide curves for 6 tidal days .......................... 46
Figure 9. Actual damage to the Flagler Beach Pier from the Thanksgiving Holiday
Storm of 1984 (Balsillie, 1985c) used to test the Multiple Shore-Breaking
Wave Transformation Computer Model for predicting wave behavior,
longshore bar formation, and beach/coast erosion ...................... 49
Figure 10. Beach/Coast nickpoint elevations for Florida ....................... 50
Figure 11. Comparison of Seasonal High Water (SHW) and Median Beach/Coast
Nickpoint Elevation (N) for the Florida East Coast ..................... 51
Figure 12. Comparison of Seasonal High Water (SHW) and Median Beach/Coast
Nickpoint Elevation (N.) for the Florida Lower Gulf Coast ................ 51
Figure 13. Comparison of Seasonal High Water (SHW) and Median Beach/Coast
Nickpoint Elevation (Ne) for the Florida Panhandle Gulf Coast ............. 51
Figure 14. Departure of Florida inlet tide data and open coast tide data ........... 53
Figure 15. Open ocean and inside astronomical tides for Ft. Pierce and St. Lucie
Inlets ..... .................................................. 54
LIST OF TABLES
Table 1. Tidal Datums and Ranges for Open Coast Gauges of Coastal Florida ...... 30 Table 2. Selected North American Datums and Ranges Referenced to MSL ........ 38 Table 3. Florida Foreshore Slope Statistics by County and Survey .............. 40
Table 4. Moment Wave Height Statistical Relationships ....................... 45
vii




....tSPECIAL PUBLICATION NO. 43
SEASONAL VARIATION IN SANDY BEACH
SHORELINE POSITION AND BEACH WIDTH
by
James H. Balsillie, P. G. No. 167
ABSTRACT
Annual cyclic fluctuations in beach width due to seasonal variability of forcing elements
(e.g., wave energy) have been a subject of concerted interest for decades. Seasonal variability can be used to 1) identify and evaluate the accuracy of historical, long-term shoreline data interpretations, 2) aid in the identification of the boundary of sovereign versus private land ownership, and 3) predict expected seasonal behavior of beach nourishment projects, which
should be a stated up-front design anticipation.
In this paper, data representing monthly averages are used to compare "winter" and
"summer" wave height and wave steepness as they relate to seasonal shoreline shifts. Coupled with astronomical tide conditions and beach sediment size, two quantifying relationships are
proposed for predicting seasonal shift of shoreline position (i.e., beach width).
INTRODUC77ON span distances of from 450 to 700 meters, and such features often migrate alongshore The configuration of the beach in at time scales on the order of days or weeks profile view is primarily due to tidal (Morisawa and King, 1974). As the bay fluctuations which cause periodic changes in between cusp horns passes a profile line, the sea level, and shore-breaking wave activity, beach becomes narrower, and as a horn Any change in wave characteristics and passes, the beach widens. A prediction direction of approach will, depending on tidal model for daily shoreline change has been stage, result in a change in the sandy beach suggested by Katoh and Yanagishima configuration. (1988).
Systematic beach changes through a Of the possible cyclic changes, single astronomical tidal cycle are well noted perhaps the most pronounced is that (Strahler, 1964; Otvos, 1965; Sonu and occurring on the seasonal scale. During the Russell, 1966; Schwartz, 1967). Cyclic cut "winter" season, when incident storm wave and fill associated with spring and neap tides activity is most active, high, steep waves (Shepard and LaFond, 1940; Inman and result in shoreline recession. Generally, the Filloux, 1960), and the effect of such berm is heightened with a gentle foreshore phenomena as sea breeze (Inman and Filloux, slope, although erosion scarps may form. 1960; Pritchett, 1976), can contribute Sand removed from the beach is deposited additional modifying influences, offshore in one or more submerged longshore bars. During the "summer" Beach changes are noted to occur at season lower waves with smaller wave time intervals longer than a tidal cycle (e.g., steepness values transport sand stored Dolan and others, 1974). Smaller beach offshore back onshore, resulting in a wider cusps, for example, may range from 10 to beach. It should be noted that along some 50 meters apart, while sinuous forms may coasts such as the approximately east-west
1




FLORIDA GEOLOGICAL SURVEY
trending coastline of Long Island, New York change have been described in terms of sand (Bokuniewicz, 1981; Zimmerman and volumne changes (Ziegler and Tuttle, 1961; Bokuniewicz, 1987; Bokuniewicz and Dolan 1965; Eliot and Clarke, 1982; Aubrey Schubel, 1987), no seasonal variability can and others, 1976; Davis, 1976; DeWall and be detected (H. J. Bokuniewicz, J. R. Allen, Richter, 1977; DeWall 1977; Thorn and personal communications). Such lack of Bowman, 1980; Everts and others, 1980; seasonal variability may be symptomatic of Bokuniewicz, 1981; Miller, 1983; sub-seasonal storm wave groups combined Zimmerman and Bokuniewicz, 1987; with an almost imperceptible climatic change Samsuddin and Suchindan, 1987), by (J. R. Allen, personal communications), contour elevation changes (Shepard and possibly exacerbated by changes in oceanic LaFond, 1940; Ziegler and Tuttle, 1961; storm front azimuths relative to shoreline Gorsline, 1966; Urban and Galvin, 1969; azimuths (Dolan and others, 1988). Nordstrom and Inman, 1975; Aubrey, 1979; Similarly, the east-west trending shoreline of Felder and Fisher, 1980; Clarke and Eliot, the northwestern panhandle coast of Florida, 1983; Berrigan, 1985; Brampton and Beven, while having annual net longshore transport 1989), and in terms of horeontal shoreie to the west, appears to be characterized by shidfts or beech width changes (Darling, daily to weekly rather than seasonal 1964; Johnson, 1971; DeWall and Richter, reversals in longshore current direction 1977; DeWall, 1977; Aguilar-Tunan and (Balsillie, 1975). It appears, therefore, that Komar, 1978; Everts and others, 1980; east-west trending shorelines pose Clarke and Eliot, 1983; Miller, 1983; considerations deserving further attention. Garrow, 1984; Berrigan and Johnson, 1985; However, for much of the Earth's open, Patterson, 1988; Kadib and Ryan, 1989). ocean-fronting shoreline seasonal changes
are clear, which constitutes the subject of Potential legal ramifications of this paper, seasonal shoreline changes as they relate to the jurisdictional shoreline boundary position
SEASONAL VARIABILITY have been addressed by Johnson (1971), Hull (1978), O'Brien (1982), and Collins and
Classically, seasonal variability is McGrath (1989). While there are other associated with California beaches where seasonal shoreline change applications theirgeometric character changes noticeably (discussed in the section on Application of from "summer" to "winter" (e.g., Shepard Results), the motivation for this work centers and LaFond, 1940; Shepard, 1950; Bascom, about derivation of a least equivocal 1951, 1980; Trask, 1956, 1959; Trask and methodology for identifying probable real Johnson, 1955; Trask and Snow, 1961; shifts in historical long-term shoreline Johnson, 1971; Nordstrom and Inman, change. 1975; Aubrey, 1979; O'Brien, 1982;
Thompson, 1987; Patterson, 1988; Collins In addition to wave height and wave and McGrath, 1989). A considerable steepness, wave direction and beach number of such studies have also been sediment characteristics can influence the conducted along the U. S. east coast (e.g., degree of seasonal beach change. Wave Darling, 1964; Dolan, 1965; Urban and direction is particularly influential for pocket Galvin, 1969; DeWall and Richter, 1977; beaches found along the U. S. west coast. DeWall, 1977; Everts and others, 1980; Along some beaches (e.g., Oceanside Beach Bokuniewicz, 1981; Miller, 1983; just north of Cape Meares, Oregon) a sandy Zimmerman and Bokuniewicz, 1987). "summer" beach is removed during the "winter" season exposing a cobble beach.
Geometric characteristics of seasonal In such cases, "summer" to "winter" grain
2




- SPECIAL PUBLICATION NO. 43
size differences are significant. In this study, located to search for a solution (Table 1). however, we shall deal with relatively
straight, ocean-fronting beaches composed First, it might be reasonable to entirely of sand-sized material, inspect the relationship between astronomical tidal conditions and horizontal
DATA AND RESULTS seasonal shoreline shift, Vs, since the tidal condition essentially constitutes a signature
In an investigation of seasonal beach characteristic for each site (i.e., it can vary changes at Torrey Pines Beach, California, considerably depending on the coast under Aubrey and others (1976) state: "No field study). Horizontal seasonal shoreline shift is studies to date have been able to adequately defined as Vs = V.,max -Vmin where Vm. is quantify these wave-related sediment the largest measurement representing the redistributions." In approaching a widest seasonal beach, and V.,i,, is smallest quantitative solution(s) to the problem, it measurement representing the narrowest becomes prudent to identify the force and beach (in this paper V is the distance from response elements involved. Basic force an arbitrary permanent coastal monument to elements are identified to be: 1) astro- the shoreline at any one time). The mean nomical tides, 2) wave height, and 3) wave range of tide, hm, (.e., the difference steepness. Response elements are: 1) vol- between mean low water and mean high ume change, 2) change in beach elevation, water), is plotted against Vs in Figure 1. or 3) horizontal shoreline shift. While the While there is scatter in the plot, a general beach sediment might be viewed as a trend is apparent. response element, given the paucity of
information about temporal/spatial sediment In addition to astronomical tide variation as it impacts this problem, it may conditions, we know that wave climate must be prudent to treat sediment characteristics be considered and that it, like tidal (within the sand-sized range) as a property conditions, varies widely from coast to element (see section on Beach Sediments for coast. Selection of values for variables further discussion). given in Table 1 can be illustrated using time series plots of monthly averages for
The response element used here is shoreline shift and wave data. An example the horizontal shoreline shift. Fortunately, for Torrey Pines Beach, California, is plotted we are dealing with a measure which, in Figure 2, which represents two years of compared to the others, has the largest concurrently observed monthly averages for range in possible values. For example, shoreline position, wave height, wave period, vertical contour changes are less than 1-1/2 and sediment data (Nordstrom and Inman, to 2 meters, and volumetric changes would 1975; Pawka and others, 1976). Further, be 3 to 4 times less than horizontal shift the data have been smoothed by a three("rule-of-thumb" guidance suggested by U. point moving averaging sequence. S. Army (1984) and Everts and others Comparison of horizontal shoreline shifts and (1980)), while horizontal shift may range up wave heights suggests that for the months to tens of meters. from about December through April storm wave activity prevailed, resulting in a
Daft narrower beach, with lull conditions from about May through October coinciding with
While the amount of data available to beach widening. Hence, the average storm quantify seasonal variation in shoreline wave height, Hs, is that occurring from position is not large, 14 data sets for which December through April, and the average lull sufficient information appears to exist were wave height, HL, is that occurring from May
3




FLORIDA GEOLOGICAL SURVEY
Table 1. Force, response, and property elements for seasonal shoreline shift analysis.
Sie s Hs H Ts TL h.,. D Q/Q
(m) (m) (m) (s) (s) m (mm) Gleneden, OR 46.9 1.14 0.72 9.2 8.1 1.91 0.35 0.815 Stinson Beach, CA 42.7 1.28 0.99 16.1 12.1 1.21 0.30 1.370 Atlantic City, NJ 32.0 1.04 0.77 7.4 7.0 1.40 0.30 0.820 Torrey Pines, CA 29.0 1.34 0.99 11.8 11.4 1.28 0.28 0.794 Goleta Point, CA 22.9 1.07 0.73 12.5 14.0 1.28 0.21 0.547 Duck, NC (1982) 18.6 1.10 0.75 8.8 8.1 1.00 0.40 0.808
(1983) 20.4 1.26 0.73 9.2 8.1 0.98 0.40 0.749 (1984) 17.4 1.15 0.70 8.7 8.4 0.96 0.40 0.654
Surfside-Sunset, CA 20.1 1.10 0.73 10.2 13.2 1.07 0.26 0.398 Huntington Beach, CA 18.3 1.14 0.99 11.6 10.4 1.15 0.21 1.078 Holden Beach, NC 15.2 0.70 0.50 6.5 7.0 1.30 0.30 0.614 Jupiter Beach, FL 10.7 1.00 0.63 5.4 5.5 0.92 0.42 0.614 Boca Raton, FL 2.4 0.64 0.51 4.9 4.5 0.84 0.90 0.933 Hollywood, FL 2.1 0.49 0.47 4.7 4.5 0.79 0.60 1.037
Vs = Seasonal range in shoreline position or beach width; Hs = Storm season average wave height;
H, = Lull season average wave height; Ts = Storm season average wave period; TL = Lull season average wave period; h,,, = Mean range of tide; D = Swash zone mean grain size: (L = Lull season wave steepness; Qs = Storm season wave steepness; CA = California, FL = Florida, NC = North Carolina, NJ = New Jersey, OR =
Oregon. Sources of data are given by beach in the text.
through October. Note that
wave period varies little 6o -. , . .-- .throughout the year for this
site. VS 40 Vs = 21.9+37.6 mrt r a 0.9302
The classic example of (m) 20o
seasonal shoreline shift
(Johnson, 1971; O'Brien, 1982) 0o o.s 1.o 20 for Stinson Beach, California, hmet (m) represents a 22-year period Figure 1. Relationship between seasonal shoreline (1948-1970), suggesting an variability, VS, and mean range of tide, hmrt. average shoreline shift of about
43 meters annually. These data are plotted inclusive) consistently result in the 43-meter against six years of wave data for the period seasonal shoreline shift reported by Johnson 1968 to 1973 (Schnieder and Weggel, (1971) and O'Brien (1982). 1982) in Figure 3. Sediment data are from a separate source (Szuwalski, 1970). Note Concurrently observed data for four that unlike the data plotted in Figure 2, wave years at Jupiter Beach, Florida (DeWall, period shows a concerted seasonal trend. 1977; DeWall and Richter, 1977) are plotted The inference may be made, therefore, that in Figure 4. It is apparent from Figure 4 that special attention should be given to seasonal lull wave heights occur from about May wave steepness values. More recent through September resulting in a wider shoreline surveys published by Collins and beach, with storm waves occurring from McGrath (1989) for three years (1984-1986 about October through at least January
4




- SPECIAL PUBLICATION NO. 43
50 U 5 =
go [5
V 75 so
70 / S
(M) 'A .0
55, (m) *60 so 55
45 so / "-*
7. 45 k.. r
1.4 40 *.
35 a
1.1 14 1.0 ND 1.3 0.9 1 .2 0.1 JO (m) .1 14 1.0
13
Figure 2. Monthly time series for Torrey 1
T 16 ( 12
115
Pines Beach, California, for shoreline"
variability, V;J A S 0 N 0 JF a aM
Period, T. ()
Fige 2Figure 3. Monthly time series for StinsTorreyon Pines Beach, California, for shoreline variability, V; variability, V; breaker height, Hb, and wave period, T. Mot,h Figure 3. Monthly time series for Stinson Beach, California, for shoreline variability, V'; producing a narrower beach. Monthly breaker height, Hb; and wave period, T. averages for wave heights and periods were concurrently measured, with a reported representative grain size. wave height and period are given by HL, and TL, respectively; similarly, storm season A single year of monthly wave data variables are given by Hs, and Ts. Wave were collected (Aguilar-Tunan and Komar, heights and periods were selected to 1978) at Gleneden Beach, Oregon, from represent conditions for the lead flanks of which a seasonal shoreline shift of about 47 seasonal accretion/recession trends, since it meters is evident. Because wave data is under these force element conditions that reported by the authors are probably responses are produced. inappropriate (i.e., they strongly appear to represent the initial offshore breaking wave Similar analyses were conducted for height), the multi-year data reported by the Boca Raton and Hollywood Beaches in U. S. Army (1984) are used. A single swash Florida (DeWall, 1977; DeWall and Richter, zone sediment size was reported by Aguilar- 1977) for four years of monthly data for V, Tunan and Komar (1978). Shoreline shift wave height and period, with mean grain and wave data are plotted in Figure 5. sizes for swash zone sediment.
These four examples illustrate how Data published for Holden Beach, wave data values were determined to North Carolina (Miller, 1983) were plotted by represent each season, where the lull season the original author so that seasonal changes
5




FLORIDA GEOLOGICAL SURVEY
20 r = r r r r 90 J-9 r 1 r
1 80 VV 70
V
60
loso
0.5 (m) 10
O
breaker height. Hb; and wave period, T. Beach, Oregon, for shoreline variability, V; breaker height, Hb; and wave period, T.
could be directly assessed by measuring peaks of change. The data represent four with simultaneously measured seasonal years of approximately monthly profiles for wave data. Sediment data are from the U. 16 alongshore profiles, with concurrently S. Army (1984). measured wave data. Sediment data are Perhaps the most complete data sets from the U. S. Army (1984). are for Duck, North Carolina, at the Coastal Engineering Research Center's Field Results for Goleta and Huntington Research Facility. All information necessary Beaches, California (Ingle, 1 966) include for this study was collected simultaneously approximately monthly surveys for a one- to result in data for three years (Miller, 1 984; year period, including beach profiles, wave, Miller and others, 1986a, 1986b, 1986c). and sediment data. Unfortunately, wave information for these sites represents For a 4-1/2 year period, Patterson only those conditions for the day profiles (1988) reports a V of 20.1 meters for
were surveyed. While information for these Surfside-Sunset Beach, Orange County, sites generally was consistent, wave period California, along with seasonal wave data from Schneider and Weggel (1982) information. Sediment grain size information were used for Goleta Beach due to is from Szuwalski (1970). unresolvable dispersion in the few daily data.
Where the specific studies discussed
Seasonal shoreline shift data for above did not provide the necessary Atlantic City, New Jersey (Darling, 1 964) astronomical tide information, these data were measured for a two-year period along were obtained from other sources (Harris,
T6
5 9
(S) (=T
iF M A M J J A S 0 N 0
month JF M A M J J A S 0 N D Figure 4. Monthly time series for Jupiter Moh Beach, Florida, for shore variability, V; Figure 5. Monthly time series for Gleneden breaker height, Hb; and wave period, T. Beach, Oregon, for shoreline variability, V; breaker height, Hb; and wave period, T.
could be directly assessed by measuring peaks of change. The data represent four with simultaneously measured seasonal years of approximately monthly profiles for wave data. Sediment data are from the U. 16 alongshore profiles, with concurrently S. Army (1984). measured wave data. Sediment data are Perhaps the most complete date sets from the U. S.- Army (1984). are for Duck, North Carolina, at the Coastal Engineering Research Center's Field Results for Goleta and Huntington Research Facility. All information necessary Beaches, California (Ingle, 1966) include for this study was collected simultaneously approximately monthly surveys for a one- to result in data for three years (Miller, 1984; year period, including beach profiles, wave, Miller and others, 1986a, 1986b, 1986c). and sediment data. Unfortunately, wave information for these sites represents For a 4-1/2 year period, Patterson only those conditions for the day profiles (1988) reports a Vs of 20.1 meters for were surveyed. While information for these Surfside-Sunset Beach, Orange County, sites generally was consistent, wave period California, along with seasonal wave data from Schneider and Weggel (1982) information. Sediment grain size information were used for Goleta Beach due to is from $zuwalski (1970). unresolvable dispersion in the few daily data.
Where the specific studies discussed
Seasonal shoreline shift data for above did not provide the necessary Atlantic City, New Jersey (Darling, 1964) astronomical tide information, these data were measured for a two-year period along were obtained from other sources (Harris,
6




SPECIAL PUBLICATION NO. 43
1981; U. S. Department of Commerce, Deguchi, 1980;Watanabe and others, 1980; 1987a, 1987b). Quick and Har, 1985; Kinose and others, 1988; Larson and Kraus, 1988; and
It is worthwhile to note that Berrigan Seymour and Castel, 1988). In this paper, and Johnson (1985) compared wave power the "summer" or lull season wave steepness computations to shoreline position for seven is expressed as QL = HL/(g TL 2), and the years of data at four localities along Ocean "winter" or storm season steepness as O)s = Beach, San Francisco, California. Deep Hs/(g Ts2). It became apparent that water wave data were measured at sites incorporation of the wave steepness ratio ranging from 3.9 to 26.7 kilometers offshore induced numerical consistency in (Berrigan, 1985). While some refraction quantitative prediction. Whether the ratio is effects may have occurred due to the San evaluated as Q$L/(s or Ps/L becomes Francisco entrance bar, there appears to be important. The form of the ratio for various a correlation between an increase in wave arrangements of relating expressions for power and decrease in beach width, assessment purposes is given in Table 2.
Hence, if (Q$L/S) < 1.0 then wave height
Results during the storm season must be more important; if (j/Cs) > 1.0 then wave
There is, from Figure 1, an indication steepness plays a stronger role. In fact, it that astronomical tides play a role in would be expected that QL/Q(S results in seasonal variability. The mean range of tide, better correlation, since beaches are eroded hmrt, and seasonal wave height difference, by steeper waves, with lower steepness AH = Hs HL, might be expressed as a sum, waves resulting in accretion. i.e., hm, + AH, or as a product, i.e., he,
(AH). Since energy according to classical In addition, beach sediment wave theory is proportional to the height characteristics have been touted to play a squared, the product, i.e., hi, (AH), might significant role. The general view is that, be more appropriate. On the other hand, the holding force elements constant, a beach sum has merit because laboratory data, if composed of coarser sediment is more stable available, could be used (i.e., since tides are than a beach composed of finer material almost never modelled in laboratory studies, (e.g., Krumbein and James, 1965; James, a product would be meaningless because the 1974, 1975; Hobson, 1977), i.e., a beach result would always be zero). In either comprised of coarser sediment should exhibit event, many combinations of parameters less seasonal variability than a beach were investigated (Balsillie, 1987b; see also composed of finer sediment (note that this Table 2 for some of the equations), and it explanation is not so straightforward, and was found that the sum was not nearly as will be addressed in greater detail in the successful as the product; either scatter was following section). Since a number of excessive as indicated by a low correlation investigators have published general coefficient, r, and/or the fitted regression line quantifying relationships which in addition to did not pass through the origin of the plot. wave height and steepness, incorporate sand size (e.g., Dean, 1973; Hattori and
Many researchers have emphasized Kawamata, 1980; Sawaragi and Deguchi, the importance of wave steepness in 1980; Watanabe and others, 1980),it would influencing the shore-normal direction of be prudent to consider granulometry in this sand transport (e.g., Johnson, 1949; Ippen study. and Eagleson, 1955; Saville, 1957; Dean,
1973; Sunamura and Horikawa, 1974; Again, it is to be noted that many Hattori and Kawamata, 1980; Sawaragi and forms of possible relating parameters were
7




FLORIDA GEOLOGICAL SURVEY
Table 2. Assessment of the wave steepness ratio for a selection of expressions
related to Vs.
Expressions Using q)L/(0S r Expressions Using (0S/0L r
hr [(AN) 0j/%] hmn + [(AN) 0%/%]
0.9339 0.7445
[h,, + (AH)] jLQ 0.8843 [hm, + (AH)] st 0.4071
hrr (AH) QL05 0.9047 h, (AH) sI'L 0.5498
h,, + [(UA) L/s] h.r + [(AM) es/*0]
D 0.8567 D 0.3837
h,. (AN) Les h,, (A) 0s/,
D 0.9672 D 0.5478
r = Pearson product-moment correlation coefficient between each expression evaluated using measured force and property element data of Table 1, and measured VS response data of Table 1.
considered in an earlier study, but that only the most successful are presented here. V = 0.025 h,,(AH) L/s (2) Incorporating the preceding considerations, D two equations are presented, the first which includes force elements only, which posits: plotted in Figure 7, wherein all variables are expressed in consistent units. In terms of dimensions, one will note that when all V, = 78.5 h,,,,, (AH) 0)/Q0 (1) dimensional cancellations are made in equations (1) and (2), length only remains. and is plotted in Figure 6. The cubic least The coefficient of 0.025 was determined squares regression coefficient (forced using the same fitting procedure as for through the origin) of 78.5 is in units of m1 equation (1). It is apparent from the figures where the mean range of tide, hmn, and that equation (2) reduces some of the scatter seasonal wave height difference, AH, are in of equation (1). The standard error (Ricker, meters. The standard deviation of the data 1973) of equation (2) in the vertical direction from the equation (1) regression line in the is 6.8 m. It may also be of interest to note vertical direction (Ricker, 1973) is 11.4 m. that the coefficient of equation (1) when The second equation includes the mean expressed relative to the coefficient of swash zone grain size, D, to yield :
8




- - SPECIAL PUBLICATION NO. 43
equation (2) results in a mean 60 grain size of 0.318 mm which, VS. 78-S hmrt (a )L/ s using the Wentworth vs 40 r o.o047 classification scheme, is a medium-sized sand (Wentworth, t 20-* 1922).
I I, I J
0 oI (2 0.3 04 0.5 0.6 07 DISCUSSION hmrt (AM) */0S (/2)
Figure 6. Illustration of mathematical fit for equation (1). A favorable result from
many of the prediction equations 60- r r r tested during the course of this vs o0.0o25 hmrt (AN) /LS V D
investigation is that most showed s = o.9a72 a trend between Vs and the relating parameters (e.g., column 1 of ) 2 Table 2). Ostensibly, such consistency should not be 0 5oo 1,00ooo so00 2000 surprising since the major factors art(,) is (m)
0
known to cause seasonal Figure 7. Illustration of mathematical fit for equation (2). variability were considered, and
the remainder of the work
involved rearranging the variables to reduce become available to further test and/or scatter. Further, the goal to delineate enhance the prediction relationships. seasonality was a simplified approach Nevertheless, the results presented here are (compared to relating the entire time series statistically valid; one should not be timid in of monthly values which becomes applying resulting computational values increasingly complex), pending future refinement in prediction methodology. One purpose of this paper is Equations (1) and (2) engender some to act as a plea for more data. Following are heterogeneity that needs discussion. Both discussions of a few concerns related to AH and OL,/s are seasonal parameters. seasonal shoreline variation predictions. Granulometry as it appears in equation (2) is a property element application, although a The Single Extreme Event and seasonal response element application is the Combed Stom Season possible and is discussed in a later section. The quantity, hmrt, however, is not a The sandy littoral zone is comprised, seasonal measure. It is, rather, an average from offshore-to-onshore, of the nearshore, approximate hourly measure where one tide the beach, and the coast. Each of these (diurnal) or two tides (semi-diurnal) occur in three subzones is created and maintained by one tidal day of 24 5/6 hours. Hence, hmrt sets of force elements normally different is also a property element that is a signature from each other within the long-term value for each site, noting that it can vary temporal framework. When a storm or significantly depending upon the locale, hurricane impacts the littoral zone, the Seasonal mean sea level change for which following scenarios are possible: 1) the there are no site-specific data for Table 1 extreme event produces a combined total localities, is discussed in a following section. storm tide which rises above the beach-coast interface elevation to affect all three The results of this work might be best subzones, 2) the combined total storm tide viewed as a first appraisal until more data does not rise above the beach-coast
9




FLORIDA GEOLOGICAL SURVEY
interface elevation but does persist long enough for the beach to be eroded and the coast is attacked by storm waves, 3) the 2combined storm tide does not rise above the beach-coast interface elevation and is short enough in duration so that only the nearshore and beach are affected, and 4) the Hb extreme event remains out at sea so that impact is indirect (i.e., a combined total storm tide does not or only fractionally (m) 0 reaches the shore) and storm waves primarily affect the nearshore and beach.
60o
The combined total storm tide used here is defined by Dean and others (1989) as the V storm surge due to astronomical tide, wind stress, barometric pressure, and breaker (m) s0 zone dynamic setup, which defines the active phenomena for scenarios 1, 2, and 3 (i.e., the sterm i de event). Scenario 4 40 .... includes only the effects of breaking wave 1 2 3 4 5 6 7 8 9 101112 activity, including dynamic wave setup, and Day is termed the stenn wave event. Scenarios Figure 8. Example of the quick response and 1 and 2 are those which, depending on recovery of the beach to storm wave storm strength, duration, continental slope, activity, Pensacola Beach, Florida, December and approach angle, usually produce the 1974;the storm peak occurred on December design erosion event (Balsillie, 1984,1985a, 7 (data courtesy of James P. Morgan, 1985b, 1986). Probabilistically, the personal communications). frequency of occurrence increases from scenario 1 to 4. 1986; Savage and Birkemeier, 1987), for events described by scenarios 1, 2 and 3 Under certain circumstances of event above. Beach recovery following the effects longevity, astronomical tides, and nearshore of a storm wave event (i.e., scenario 4) was slopes, exceptions can occur. One such recorded by James P. Morgan at his exception occurred when Hurricane Gilbert Pensacola Beach, Florida, home (Figure 8); struck Cancun, Mexico in 1988. Because within a day following storm wave there is essentially no continental shelf and abatement, the beach had recovered to its nearshore slopes are steep, all eroded sand pre-storm width. from Cancun's beaches was removed and natural beach recovery was not possible. The magnitude of seasonal shoreline Potentially, other exceptions can occur change mayvaryfrom year-to-year, since for where, for instance, submarine canyons any site some years may have more frequent might act as a sediment transport conduit and intense storm tide and wave activity and sand is irremeably lost from the littoral than other years. Horizontal shoreline shifts system. For most shores, however, due to direct storm and hurricane impacts continental shelves are wide and nearshore are now usually recorded. However, for slopes gentle enough that beach recovery to storms that do not directly impact the shore pre-storm dimensions following single storm (i.e., are far out at sea, for example Tropical impact occurs in a period of one to several Storm Juan (Clark, 1986) which affected days (Birkemeier, 1979; Bodge and Kriebel, Florida) but generate storm waves that do
10




- SPECIAL PUBLICATION NO. 43
cause shoreline erosion, such , , erosion is usually not measured, a EXTREME EVENT TYPE
Dolan and others (1988) o Extratropical (Dolan,. Lins, and conducted an extensive study on Hayden, 1988) 1942-1984 extratropical storm activity, a Tropical (Neumann et al.
*Hurricane 1981) 1940-1980
assessed also in terms of storm H ne 1981) 1940-190 wave hours, for 41 years of data g
(1942 to 1984) along the Outer 4 Banks of North Carolina. These .
data (Figure 9) show a concerted 2 seasonal trend. In addition, the Total author extracted from Neumann 3' and others (1981) tropical storms X and hurricanes whose tracks A
E
came within about 250 miles of / the Outer Banks for the period & 21940 to 1980. These latter data, \ also plotted in Figure 9, are added / to the extratropical data (plotted / as a bold, solid line). Hence, the 1 total storm record is nearly represented and, except for only p-a few direct impacts, represent .4- storm wave events (i.e., scenario o ---" $ e-",
4 above). For the mid-Atlantic, JAN FEB MAR APR MAY JMUN JUL AUG SEP OCT NOV DEC about 35 storms occur per year Month on the average (about 26 winter Figure 9. Monthly average occurrences of extreme event events and 9 summer events), wave events for the Outer Banks of North Carolina. 93% of which are extratropical
events. In terms of storm wave duration, Beach Sediments Dolan and others (1988), determined using hindcast techniques that on the average, Beach sediments engender some storm waves occur for about 571 hours per interesting concerns. How we consider year (i.e., 24 days per year) for extratropical sediments depends upon whether storms off of the Outer Banks; winter storm granulometry is applied as a property waves persist for an average of 433 hours element or a response element, which in turn (i.e., 18 days), and summer storm waves has an effect on the dimensional about 156 hours (i.e., 6.5 days). These data configuration of a numerical representation. strongly correlate with the expectation of As an example, equation (1) requires an wider mid-Atlantic east coast summer additional parameter with units of L'1 for the beaches and narrower winter beaches, and equation to be unit consistent. Equation (2) illustrate the important fact that a large was rendered unit consistent by dividing by number... not a few ... winter storm events a granulometric parameter with a length are required to maintain a narrower winter dimension. If this is to be the applied case, beach relative to a wider summer beach. it is useful to note that when sedimentologic grain size is specified in S. I. units, the mean grain size and standard deviation moment measures have units of mm, while
11




FLORIDA GEOLOGICAL SURVEY
skewness and kurtosis are Table 3. Mean annual beach grain size (foreshore dimensionless. Otherwise, the slope samples) from monthly data, and range in size. granulometric moment measures can Annual Range be specified all in dimensionless phi Site D (mm) of D Source units. (mm) FLORIDA
Beach sands characteristically ..
h Bearang ians r mtl St. Andrews St. Pk. 0.29 0.04 Balsillie, 1975 have a range in size from 0.1 mm to Grayton Beach 0.37 0.13 Grayton Beach 0.37 0.13 .
1.0 mm (U. S. Army, 1984) which Crystal Beach 0.37 0.15 occupies about 46% of the sand- J. c. Beasley St. Pk. 0.40 0.11 sized range of Wentworth (1922; Navarre Beach 0.41 0.14 i.e., 0.0625 to 2.0 mm). From Table Fort Pickens Beach 0.43 0.27 3, it is apparent that the range in NORTH CAROLINA mean grain sizes occurring over an Duck 0.401 0.19 Miller, 1984 annual period is less than 1/3 of the .. commonly found range in beach sand GeP ac. 1 CA UFORNIA size (i.e., 0.9 mm). Therefore, the Goleta Pt. Beach 0.21 0.16 Ingle, 1966 Trancas Beach 0.22 0.18 typical annual mean grain size, D, for Santa Monica Beach 0.26 0.29 any beach might be an appropriate Huntington Beach 0.21 0.14 measure to consider as a property La Jolla Beach 0.17 0.04 element provided that sufficient
samples are available annually to Table 4. Two cases of sedimentologic obtain a reliable measure (e.g., a suite of response of moment measures to wave monthly samples). This implies that there enerY levels. needs to be a real difference in mean grain sizes from site-to-site for the application to CASE 1 CASE 2 have meaning. Even so, the use of mean Em Lae A ot EW Leive tAr twcesive fto flat Excessiv. to
grain size alone without consideration of s.anini s leenaogc standard deviation, skewness and kurtosis epos Rspons remains somewhat of a curiosity other than:
. MEAN GRAIN SIZE
1. its use results in a good fit for equation
(2), 2. is properly applied in equation (2) Ds DL DS > DL (i.e., the larger the value of D, the smaller SKEWNESS sKEWNESS
becomes Vs), 3. produces the proper unit dimensions for the equation, and 4. has sks SkL Sks < SkL been a considered variable in other research KURTOSIS
KURTOSIS
results.
Ks < KL KS < KL
It is generally the case (CASE 1 ofKS It is generally the case (CASE 1 of NOTES: Subscripts S and L refer to the storm season Table 4) that the coarsest beach sand is and lull season, respectively. The corresponds to found in the swash zone, and which is the symbol, -, is meant to signify that the measure did only type of sample considered here since it not change due any recognizable response to energy directly represents energy expenditures of level force element changes. the littoral hydraulic environment. One might suspect that swash samples are coarser during the storm than the lull season. However, the range in sediment commensurate with bulk properties meeting size within the sand-sized range is limited for conservation of mass and energetics any beach to the coarsest available material constraints (Passega, 1957, 1964). In fact,
12




- SPECIAL PUBLICATION NO. 43
the negligible effect of sand-sized material on 1" .56 I w 1 runup for larger waves has been noted by ,.2s Savage (1958). His results strongly imply ., I- that relative to sand size, as the wave height *.7 T..s 5h. CA increases there is reached a point beyond os which sediment size within the sand-sized T i4
12
range no longer discriminately responds. That is, the level of wave energy is overpowering even to the coarsest fraction o.3 of sediment available within the sand-size range. o.7
0.76
Hence, unless the wave climate is closely in equilibrium with sediment comprising the beach, one would not necessarily expect to find significantly T correlative seasonal changes in mean grain is size (or for that matter skewness, although 2 ..L it might be somewhat less sensitive to ., energy) within the sand-size range. The .. I. ll II 111 author located data where at least monthly J A JJ ASO. D J FMAUJ JASoND sand samples were collected with concurrent m m"
Fgure 10. Typical examples of time series relation wave data for sites along the U. S. west, of monthly data for breaker height, wave period, east, and Gulf coasts. There was no and foreshore slope grain size for California (data discernible seasonal correlation between from Ingle, 1966) and northwestern Florida waves and mean sediment grain size. panhandle (data from Balsillie, 1975) sites. Several typical examples are illustrated in Figure 10.
which may or may not differ from the Samsuddin (1989), however, reports characteristically rounded, quartzoseto have found correlation between seasonal feldspathic U. S. beach sands considered in changes in wave conditions, foreshore slope, this work. and sand-sized textural changes along the southwest Kerala coast of India, wherein There also occurs the case (CASE 2, mean grain size increased and kurtosis example 2) where a beach is comprised of decreased during higher seasonal wave sediments exceeding the sand-sized range. energy conditions (CASE 2, example 1). An example is Oceanside Beach, Oregon, Samsuddin's one-year investigation, in which mentioned earlier, in which all the sand-sized beach foreshore sand was seasonally summer beach material is removed to expose sampled, may have been a fortuitous year in a winter cobble beach. Under such which equilibrium conditions were more conditions, one would expect that sediment nearly manifest. Kerala sand samples are coarsening, as reflected by the mean grain also characterized by a consistently large size and skewness, would result from higher standard deviation which allows for greater wave energy levels because of the excessive leeway in sorting potential (0.6 to 0.7 phi size of coarser sediments. compared to 0.2 to 0.55 phi commonly found for U. S. beach sands). Unfortunately, When singularly considered, the 1st Samsuddin did not describe the mineralogy moment measure (mean grain size) tells us or shape characteristics of the samples nothing about the nature of the distribution.
13




FLORIDA GEOLOGICAL SURVEY
The 2nd moment measure (standard where the moment measures are defined in deviation) tells us about the dispersion about Table 4. The 3rd moment measure the 1st moment measure, but leaves no (skewness) of equation (3) has a value of 20 insight as to how the distribution departs added to it in order to assure that positive either symmetrically or asymmetrical from values will result. The parameter 0 when the normal bell-shaped frequency curve (or evaluated using S. I. units has units of L-1 from the straight line for the cumulative (dimensionless units result when curve plotted on standard probablity paper). granulometric measures are evaluated in phi Such departure is a characteristic of the tails units). By using seasonal values of 0, that of the distribution about which knowledge is is, 0s for the storm season and 6L for the lull progressively imparted to us by considering season, it may be possible to compile a the 3rd moment measure (skewness), 4th sedimentologic response element parameter moment measure, (kurtosis), and higher that can be incorporated into equation (1). moment measures (Tanner, personal The proper form of the parameter, including communication; Balsillie, 1995). It is, in equation (3), however, requires additional fact, the tails of the distribution which can data, research, and testing. provide a great deal of environmental
information. It has been demonstrated, for Astronomical Ts instance, that there is an inverse relationship
between the kurtosis and the level of surf That mean astronomical tide wave energy expenditure (Silberman, 1979; elevations exhibit cyclic seasonal variability Rizk, 1985; Rizk and Demirpolat, 1986; has long been established (Marmer, 1951; Tanner, 1991, 1992). Tanner (1992) has Swanson, 1974; Harris, 1981) and is reported a correlation between sea level rise included in tide predictions. The U. S. and kurtosis, because the rise component is Department of Commerce (1987a, 1987b) attended by an increase in surf wave energy states, however, that at "... ocean stations expenditure. the seasonal variation is usually less than half a foot." Mariner (1951) notes that
From the preceding discussion, it is seasonal variation in terms of monthly mean apparent that two general cases can be sea level for the U. S. can be as much as identified where wave energy levels either 0.305 m (1 foot; Table 5); some examples exceed stability constraints of the coarsest for the U. S. east, Gulf, and west coasts are fraction of the sedimentologic distribution, or illustrated in Figure 11. Based on the many they do not. For three moment measures years of monthly data, researchers (Marmer, considered to best represent sedimentologic 1951; Harris, 1981) note slight variations in response to the wave energy force element, the seasonal cycle from year-to-year, but storm and lull season responses are listed in also recognize the periodicity in peaks and Table 4. For the two cases (Table 4) only troughs over the years. For much of our the kurtosis persists in providing a response, coast, lower mean sea levels occur during because the 4th moment measure is not the winter months and higher mean sea rendered ineffective to register a change by levels during the fall. Harris (1981) excessive wave energy levels. Therefore, a inspected the record to determine if storm parameter for consideration that more nearly and hurricane occurrence was in any way quantifies sedimentologic response might be responsible for the seasonal change, but given by: found "... no systematic variability". Galvin (1988) reports that seasonal mean sea level
S-20 + Sk) K (3) changes are not completely understood, but
D suggests that there appears to be two primary causes for lower winter mean tide
14




SPECIAL PUBLICATION NO. 43
levels for the U. S. east coast: 1. strong Table 5. Seasonal range in monthly northwest winter winds blow the water average water levels. away from shore, and 2. water contracts as it cools. He notes that winds re e more Sit No h important in shallow water where tide Yea-s (m) gauges are located, but that contraction u. s. Ewt Comt becomes important in deeper waters.
Swanson (1974) also notes "... seasonal New York 19 0.177 Feb Sep
changes resulting from changes in direct Atlantic City 19 0.165 Feb Sep
changes resulting Baltimore 19 0.238 Feb Sep barometric pressure, steric levels, river Norfolk 19 0.177 Feb Sep discharge, and wind affect the monthly Charleston 19 0.253 Mar Oct variability." Mayport 19 0.314 Mar Oct Miami Beach 17 0.259 Mar Oct
Seasonal variation in tides is usually u. s. CA coast attributed to two harmonic constitutents:
one with a period of one year termed the Key West 19 0.216 Mar Oct solar annual tidal constituent, and the other Cedar Key 10 0.244 Feb Sep Pensacola 19 0.232 Feb Sep
with a period of six months termed the solar Galveston 19 0.247 Jan Sep semiannual constituent (Cole, 1997). Some Port Isabel 4 0.262 Feb Oct consider these to be meteoroligical in nature, U rather than astronomic. However, because u.s. wet coast the root cause of cyclic seasonal weather is Seattle 19 0.159 Aug Dec the changing declination of the sun, they Astoria 19 0.219 Aug Dec should more nearly be astronomical in origin. Cresent City 14 0.180 Apr Dec
Harmonic analysis of the annual tidal record San Francisco 19 0.104 Apr Sep
Harmonic analysis of the annual tidal Los Angeles 19 0.152 Apr Sep can easily determine the amplitude and La Jolla 19 0.143 Apr Sep phase of each of these constituents, thereby San Diego 19 0.152 Apr Sep providing a mathematical definition of the Notes: 1. h = seasonal range based on average of n seasonal variation. (George M. Cole, years of monthly means where monthly means are personal communications.) average of hourly heights; 2. San Diego gauge is located in San Diego Bay; 3. Astoria gauge is located 15
Comparing the closest appropriate miles upstream from the mouth of the Columbia River. curve from Figure 11 to Figures 2 through 5,
it is apparent that the lowest seasonal stand
of mean sea level and, therefore, average occur (e.g., low monthly average mean sea astronomical tide effects occurs when the level wider beaches, and high monthly beach is narrowest for Stinson Beach and average mean sea level narrower beaches) Torrey Pines Beach, California, and Jupiter then a relating parameter needs to be Beach, Florida. For Gleneden Beach, incorporated in the quantifying predictive Oregon, narrow beach widths and monthly relationship(s). It is of consequence to note, average tidal highs seem to be more nearly in for the data of Tables 1 and 4, that the phase. Therefore, it is not clear that seasonal range of monthly average mean sea seasonal changes in astronomical tides level is from 9 to 33% of the mean range of significantly affect seasonal shoreline tide (hmrt). variability, at least not in terms of average monthly measures. Quite clearly, however, APPLICATION OF RESULTS such data needs to be procured for each site to confirm a correlation or lack thereof. While horizontal shoreline shift (or Should the proper correlation consistently beach width change) addresses only one
15




FLORIDA GEOLOGICAL SURVEY
J-6
m ASTORIA
KEY WEST
ALATICR CEIAT KEY 4
A L,.. =: ,.o.ft. o,
ONCHARLESTON
MAYPORT A
LA JOLLA
PORT ISAGEL
AAN DIEGO
U. EAST COAST U. S. GULF COAST u- S. WEST COAST
ILll i fLl lLAl A 1 kl l J5FMAMJJAAUOND JPMAMIJJASOND J FMAMJJAUOND MONTH
Figure 11. Monthly variation in sea level for the contiguous United States (after
Marmner, 1951).
dimension of a measure of beach change, it agency. The results of this paper provide a does serve to straightforwardly punctuate quantitative basis upon which to inform the the nature of the phenomenon. The manner public, and a method to assess a permit of approaching quantification of the application. phenomenon here, allows for a simply applied methodology that is useful for Seaward Boundary of Public educational, technical, and planning versus purposes. Private Ownership
General Knowledge The boundary between private (i.e., upland) and public (i.e., seaward) beach Seasonal beach shifts are not ownership is fixed by some commonly generally known by the layman. In Florida, applied tidal datum. For most of the U. S. with 35,000 new residents arriving monthly this is the plane of mean high water (MHW) (Shoemyen and others, 1988), new coastal which, when it intersects the beach or coast property owners have been alarmed after forms, the mean high water line. However, purchasing ocean-fronting property during unlike other riparian ownership the "summer" when their beach is wide, to determinations (i.e., fluvial, lacustrine and find or return to find a narrow "winter" estuarine), littoral properties must, in beach, believing that they have unwittingly addition, contend with significant wave purchased eroding property. Ostensibly, this activity that seasonally varies. Hence, might result in an application for a permit to ocean-fronting beaches all-too-often construct a coastal hardening structure such experience cyclic seasonal width changes of as a bulkhead or seawall without a magnitude long recognized as problematic investigating seasonal beach width variation in affixing an equitable boundary (Nunez, on the part of the applicant, the applicant's 1966; Johnson, 1971; Hull, 1978; O'Brien, design professional, or the permitting
16




SPECIAL PUBLICATION NO. 43
1982; Graber and Thompson, 1985; Collins boundary between public tidelands and and McGrath, 1989). private uplands ... (it should he understood that such a boundary, while relatively stable,
would not be permanently fixed but would be
Many investigators have suggested ambulatory to the extent there occurs longthat the legal boundary for ocean-fronting term accretion or erosion). beaches should not be continuously moving
with the seasonal changes, but should be Collins and McGrath also discuss the most landward or "winter" line of mean special issues such as shore and coastal high water (Nunez, 1966). Selection of the hardening structures, artificially induced "winter" MHW line would be the most accretion of sand, etc., and their work is practical to locate and would be the most highly recommended for further reading. protective of public interest by maintaining
maximum public access to the shoreline However, no formal legal adoption of (Collins and McGrath, 1989). the littoral MHW boundary has found nationwide acceptance. This is symptomatic of
In Florida, the ocean-fronting legal mankind's tendency to give credence to boundary seasonal fluctuation issue was codes of anthropic conduct through the deliberated upon in State of Florida, LawsofMan (published in local codes, state Department of Natural Resources vs Ocean statutes, and federal regulations, etc.) but to Hotels, Inc. (State of Florida, 1974) as it essentially ignore the environment and how related to locating the MHW line from which it works through the Laws of Nature a 50-foot setback was to be determined. (published in scientific papers and journals). Judge J. R. Knott, upon consideration of all Until a balance is more nearly achieved, we the options, rendered the following decision: shall continue to exacerbate the environmental crisis that has befallen us all.
This court therefore concludes that the winter The results of this paper provide for one and most landward mean high water Ene small aspect of the behavior of nature an must be selected as the boundary between opportunity to achieve a balance between
the state and the upland owner. In so doing tt toac
the court has had to balance the pubic policy the two sets of laws.
favoring private littoral ownership against the
pubic policy of holding the tideland in trust Long-Trnm Shorelne Changes
for the people, where the preservation of a
vital public right is secured with but minimal The initial motivation to investigate
effect upon the interests of the upland owner. this subject was the development of a
this subject was the development of a
A 1966 California Court of Appeal methodology to analyze and assess longdecision rejected the application of a term shoreline changes. Quantitative continuously moving boundary in Peole vs behavior of long-term shoreline change to Kent Estate (State of California, 1966). assess coastal stability is best accomplished However, no decision has been rendered as using actual historical surveys. In Florida, as to what line to use (Collins and McGrath, many surveys as possible are located for the 1989). More recently, however, Collins and period from about 1850 to present (aerial McGrath (1989) report: photography is used where an historical hiatus occurs), usually resulting in from 8 to
The Attorney General's Office in California 14 points to represent the historical shoreline has offered its informal opinion that, if position (Balsillie, 1985a, 1985b; Balsillie squarely faced with the issue, California and Moore, 1985; Balsillie and others, courts would follow the reasoning in the 1986). These data are assessed alongshore FRodda case and adopt the "winter and most at a spacing of approximately 300 m.
landward line of mean high tide' as the legal Hence, historical change rate analysis
17Hence, historical change rate analysis
17




FLORIDA GEOLOGICAL SURVEY
requires both a temporal analytical magnitude that we must keep the number of component and a spatial analytical computational steps to a minimum in order component. to minimize the propagation of error in computing (bear in mind that in addition to Of the numerical methods available to the tempral analytical component a spatial analyze such data, many can actually component remains, which further increases magnify the uncertainty and/or error analytical computation). associated with the final results of an involved computational approach. Caution The "bottom line" is that we need to with respect to this aspect of analysis use the most appropriate and cannot be over emphasized. In fact, the computationally simple analytical topic is so important that a series of methodology available. The most standard equations for assessing the appropriate statistical analytical tool is propagation of error in computing have been undoubtedly end analysis which already provided in the Appendix. includes measures of determining the associated error or variability. In addition, The nature of historical shoreline what we might learn and quantify about location data is such that there is associated nature's own systematic variability can be error and variability. Surveying error used to our advantage both in terms of includes inherent closure errors, error due to assessing the acceptability of data, and as older technologies, and non-adjustment error an analytical tool. Such is the usefulness of for more recent vertical and horizontal epoch horizontal seasonal shoreline change. readjustments. Survey nets established for county surveys may not precisely relate to An example of temporal analysis is adjacent county nets as they would in a illustrated in Figure 12 for a locality about state-wide net. Long-term sea level 2.7 kilometers south of a major inlet on the changes, though slight, affect long-term east coast of Florida. Equation (1) was shoreline changes. These sources of error evaluated using the appropriate wave data of may be called map-source errors
after Demirpolat and others
(1989), for which a magnitude of 400 -a: -6.25 m/yr c: -0.4S m/yr 9 to 15 m may be appropriate b: +110 m/yr d: +1.64 m/yr (Demirpolat and others, 1989). Artificial Nourishment Interpretive plotting of errors of 3
shoreline location (depending on 3
data concentration) on original Jetty ConstructionBegansurvey maps must be assumed, v J especially for older maps. 200 Inlet Artificially Cut Present digitizing technology ( b \ results in an error of 3 to 4 m (Demirpolat and others, 1989). 100 ..--Except for recent -'technologies, magnitudes of errors for examples suggested 1900 19s50 2000 above are not known with Year certainty in the majority of cases. Figure 12. Example of long-term shoreline change rate Even so, it can be envisioned that (solid lines) temporal analysis using seasonal shoreline they are of sufficiently large shift data (dashed lines); see text for explanation.
18




SPECIAL PUBLICATION NO. 43
Thompson (1977) and tidal data from nearby adjacent sites are required to assure Balsillie (1987a). To the result, one standard quantification of representative shoreline deviation was added to yield a predicted change. seasonal variability measure of 50.5 m.
Starting with the most recent data and Project Design and moving back in time, regression techniques Performance Assessmnent are used to determine a trend line (solid line
in Figure 12) about which plus and minus Both long-tenm changes and extreme one-half the seasonal variability measure is event impacts have long been considered in affixed in the vertical direction (dashed lines assessing coastal development design in Figure 12). The slope of the trend line of activities (until recently the former has bythe time series is the rate of erosion or and-large been qualitative). In proper order, accretion (a zero slope or horizontal line long-term changes should first be represents stability). Now the seasonal determined, followed by the design extreme variability measure becomes a valuable asset event impact. The first determination allows towards identifying spurious data or long- for prudent siting of the development term change segments in shoreline behavior, activity, and the second for responsible For instance, if a point lies outside the structural design solutions to withstand seasonal variability envelop in the middle of storm tide, wave, and erosion event impacts. segment d, one would conclude that either However, without knowledge of seasonal seasonal variability was extreme for that asreve safits for a particular locality, year (for which there are undoubtedly no uncertainty will be introduced into such records) or the survey was made assessment. Following long-term immediately following extreme event impact determination of where the shore will be (either storm tide or wave event for which (e.g., say, a standard 30-year mortgage there are probably no records). In either period) it would, for instance, be prudent to case, we have reason to not include the data adjust the beach width of a given point in our analysis, since there are topographic survey to its narrowest expected sufficient data points for the segment to seasonal dimension, then to apply extreme suggest a strong trend. Interactively, trends event analyses. Considering the significant in segment d at localities up- and down- outlay of resources for beach nourishment coast can be used to verify such a trend in projects, it would seem appropriate to the spatial component of the change rate consider seasonal shoreline variability both in analysis. project design and in assessing performance.
We also can use historical information The controversial issue of whether about the area to assist in analysis. For coastal hardening structures (e.g., seawalls, instance, we know that the inlet was bulkheads, revetments) promote the erosion artificially constructed in 1951, and jetty of beaches fronting them, is one of complex construction began in 1953. Furthermore, proportions. Without being long-winded, the artificial nourishment south of the inlet began issue might finally be resolved by inspecting in 1974. Each of these events is coincident long-term shoreline location data. Again, with a new episode in shoreline behavior, however, seasonal shoreline shifts would and may be verified with similar analyses at require quantification and application in the nearby up- and down-coast sites. Note that analysis. At the very least, methodology there are too few data points to quantify the developed here would allow one to shoreline change trend for segment c; either determine if seasonal shoreline change was additional data points are required or of significant proportions that it should be verification/readjustment from analyses at considered in design applications. Using
19




FLORIDA GEOLOGICAL SURVEY
known wave, tidal, and sedimentological including seasonal wave approach angle data it would be a straightforward task to changes, and data for beaches composed of compile such results, particularly in Florida sand and pebbles (i.e., a very large standard where the coast has been monumented, deviation) would help in understanding the role of the sedimentologic property element.
CONCLUDING REMARKS
ACKNOWLEDGEMENTS
For much of our shoreline, seasonal
shifts in shoreline position occur. While the Review of an earlier manuscript phenomenon has been the subject of leading to this paper provided significant considerable concern, no specific guidance, and those comments and quantification has, until now, surfaced, suggestions from Paul T. O'Hargan, Joe W.
Johnson, George M. Cole, Alan W.
It has been noted earlier that some Niedoroda, and Gerald M. Ward are gratefully shorelines (e.g., east-west trending shores) acknowledged. James R. Allen and Ralph R. apparently do not exhibit seasonal shifts. Clark, and William F. Tanner reviewed the This may be due to storm wave impacts present form of the paper and made several occurring in groups for periods of less than valuable suggestions. Special thanks are monthly and/or due to climatic change also extended to Kenneth Campbell, Ed affecting storm front azimuths relative to Lane,Jacqueline M. Lloyd, Frank Rupert, and shoreline azimuths. Correlation might be Thomas M. Scott of the Florida Geological attained by selecting most and least active Survey for the many useful editorial monthly averages, or by applying moment comments. statistics.
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20




SPECIAL PUBLICATION NO. 43
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APPENDD: PROPAGATION OF ERRORS IN COMPU7NG
(compiled from formulations in Barry, 1978)
Where R is the result of some numerical AVERAGE operation (e.g., addition, subtraction, multiplication, division, power function, E + + + ...+ E average, etc.) for measured quantities N,, = n N2, N3,...,Nn, each with associated measurement errors E,, E2, Ez,. .. ,E, CONSTANT ERROR respectively, then the total error E,, is applied as: where E = E, = E2 = E3 =...= E,
R E,, E = Era
where E, is determined according to: POWER
ADDITION OR SUBTRACTION where (R + EP)" = (N1 + Ej)m
E 2 + + +...+( E = E, Na'
PRODUCT OR QUOTIENT ROOT
E E2 2 E 2 where (R + E,)"m = (N, + E,)'"m E = R + + + E1 "'
N2 3 Et = m-1 E28
2 8




SPECIAL PUBLICATION NO. 43
OPEN-OCEAN WATER LEVEL DATUM PLANES:
USE AND MISUSE IN COASTAL APPLICATIONS
by
James H. Balsillie, P. G. No. 167
ABSTRACT
Swanson (1974) notes that tidal datum planes "... are planes of reference derived from the rise
and fall of the oceanic tide". There are numerous tidal datum planes. Commonly used datums in the United States include the planes of mean higher high water (MHHW), mean high water (MHW), mm didelevfd (MTL), nei a- Aevaf (MSL), nwa Jew water (MLW), and m~ean Jlower low water (MLLW). Each datum is defined for a specific purpose or to help describe some tidal phenomenon. For instance, MHW high water datums have been specified by cartographers in some states (e.g., Florida) as a boundary of property ownership. Low water datum planes have been used as a chart datum because it is a conservative measure of water depth and, hence, provides a factor of safety in navigation. High water tidal stages have historically been of importance because they identified when sailors should report for duty when 'flood tide"
conditions were favorable for ocean-going craft to leave port, safely navigate treacherous ebb tidal shoals, and put to sea. Not only do tidal datum specifications vary geographically based on local to regional conditions for purposes of boundary delineation, cartographic planes, design of coastal structures, and land use designations, etc., but they have changed historically as well. Moreover, given ongoing technological advancements (e.g., computer-related capabilities including the advent of the personal computer), how we approach these data numerically is
highly important from a data management viewpoint.
IN7RODUC77ON Florida are problematic because there are a limited number of gauging stations to Tide gauges are usually located in water represent astronomical tidal phenomena. bodies connected to the oceans, such as While it has been standard practice to estuaries and rivers, and may even be used to linearly interpolate open ocean tidal datums record seiches such as those occurring in the between gauges, such an approach is not Great Lakes. Here, however, the concern is recommended should the gauges be spaced with open ocean es. Open ocean tide further apart than about 6.2 miles (Balsillie gauges are defined "... as those gauges sited and others, 1987a). Of the 33 currently directly upon the open ocean nearshore available open ocean gauges in Florida (Table waters and subject to the influence of ocean 1), only three pairs of stations meet this processes, excluding those under the constraint. In fact, the average distance influence of inlet hydrodynamics..." (Balsillie between Florida open ocean tide gauges is and others, 1987a, 1987b, 1987c). The 27.4 miles. Ostensibly, the 6.2-mile latter constraint in the definition is included constraint is recommended since even though it is difficult to determine the concurrently similar tidal stage datum extent of influence from inlet to inlet, elevations can vary significantly over segments of the coastline when this distance Open ocean tidal datum applications in
29




FLORIDA GEOLOGICAL SURVEY
Table 1. Tidal Datums and Ranges for Open Coast Gauges of Coastal lorida
(Updated in 1992 after Balsie, Caden and Watters, 1987a, 1987b, 1987c).
Open State Plane MHIMW MHW MT MLW MLLW Coatinates .MTR X Station Name co] [(
Gauge Easting Northing (F (Feet) (Miles) (Feet) (Feet)
FLORIDA EAST COAST
Femandina Beach 0061 362649.81 2287406.62 3.52 311 0.25 -2.61 -- 5-72 5.831 Little Tabot Island 0194 372355.76 2216450.20 3.60 3.30 0.55 -2.19 -2.35 5.49 19.753
Jacksonville Beach 0291 377952-02 2163090.54 3.25 2.94 0.39 -2.17 -2.33 5.11 30.150
St. Augustine Beach 0587 417053.67 2008422.56 2.73 2.48 0.15 -2.17 -2.33 4.62 60.491
Daytona Beach 1020 498405.18 1779242.33 2.52 227 0.19 -1.88 -2.06 4.15 106.820 Daytona Beach Shores 1120 511704.59 1749549.40 2.44 2.06 0.07 -1.89 -2.06 3.98 112.990
Patrick Air Force Base 1727 628785.91 1421930.52 2.27 2.09 0.32 -1.45 -1.61 3.54 185.030
Eau Gallie Beach 1804 619782.34 1383121.82 225 2.07 0.33 -1.33 -1.49 3.40 191.810 Vero Beach 2105 707153.65 1213218.30 2.01 1.89 0.19 -1.51 -1.67 3.40 227.560
Lake Worth Pier 2670 815854.41 829171.49 1.93 1.87 0.47 -0.93 -1.10 2.80 304.910
Hillsboro Inlet 2862 800981.65 700015.89 1.79 1.73 0.43 -0.87 -1.03 2.60 329.700
Lauderdale-by-the-Sea 2899 797331.41 675151.18 1.99 1.93 0.63 -0.67 -0.83 2.60 334.580
North Miami Beach 3050 789219.52 581194.67 1.77 1.71 0.46 -0.79 -0.96 2.50 352.520
Miami Beach (City Pier) 3170 785773.29 522409.95 1.76 1.67 0.42 -0.84 -1.00 2.51 363.780
NOTE: X is the shoreline distance in miles south of the center line of St. Mary's Entrance Channel (origin: nothing = 2317969.50 feet; easting = 366516.31 feet).
FLORIDA LOWER GULF COAST
Bay Port 7151 291286.83 1527111.33 2.31 1.88 070 -0.48 -0.97 2.36 4.472 Howard Park 6904 241667.70 1389244.60 1.87 1.50 0.43 -0.64 -1.19 2.14 33.555
Clearwater 6724 231561.35 1325079.09 1.62 1.29 0.33 -0.64 -1.17 1.88 46.634
Indian Rocks Beach Pier 6623 224898.87 1295432.55 1.50 1.13 0.25 -0.63 -1.15 1-76 52.650
St. Petersburg Beach 6430 261046.14 1218243.36 1.52 1.16 0-42 -0.32 -0.83 1.48 69.560
Anna Maria 8243 268746.05 1150335.15 1.52 1.20 0.45 -0.29 -0.76 1.49 83.284
Venice Airport 5858 352475.83 995445.81 1.35 1.07 0.36 -0.35 -0.84 1.42 117.918
Captiva Island, South 5383 351707.10 779777.00 1.52 1.27 0.42 -0.42 -0.94 1.69 163.464
Naples 5110 563431.54 652958.84 1.81 1.55 0.50 -0.54 -1.17 2.09 205.226
Marco Island 4967 589299.92 572441.43 1.96 1.71 0.56 -0.59 -1.20 2.30 222.015
NOTES: 1. X is the shoreline distance in miles south of an arbitrary location in Hemando County, FL.
(origin: northing = 1551271.53 leet; easting = 287952.53 feet).
2. State Plane Coordinates and distances are based on Zone 3 transformations where necessary.
FLORIDA NORTHWEST PANHANDLE COAST
Dauphin Island 5180 472269.39 871380.81 0.87 0.82 0.26 -0.29 -0.34 1.11 -33.347
Gulf Shores 1269 467866.88 999712.52 1.20 1.13 0.50 -0.12 -0.18 1.25 -9.228
Navarre Beach 9678 508373.97 1254261.65 1.20 1.13 0.50 -0.14 -0.21 127 39737 Panama City Beach 9189 434604.55 1579274.67 125 1.18 0.54 -0.09 -0.14 127 104489 St. Andrews Park 9141 414248.96 161065122 1.16 1.06 0.47 -0.12 -023 1.18 111.489 Mexico Beach 8995 346061.53 1706517.15 1-06 1.00 0.41 -0.17 -0.22 1.17 134.479
Cape San Bias 8942 244076.07 1726862.58 1.01 0.99 0.30 -0.38 -0.38 1.37 162.615
Alligator Point 8261 32549124 2035385.12 1.73 1.49 0.53 -0.44 -1.02 1.93 232.302 Bald Point 8237 344903.70 2050145.99 2.09 1.76 0.62 -0.52 -0.98 2.28 238.633
NOTE: X is the shoreline distance in miles east of the Alabama/Florida border (origin: northing = 478050.00 feet; easting = 1047360.00 feet).
GENERAL NOTES:
1. Tidal datums are referenced to NGVD of 1929.
2. Source of information Bureau of Survey and Mapping. Division of State Lands. Florida Department of Environmental Protection, for the National Tidal Datum Epoch of 1960-1978.
3. MLLW = mean lower low water MLW = mean low water MTL = mean tide level, which along the open coast = MSL = mean sea level;
MHW = mean high water: MHHW = mean higher high water; MTR = mean range of tide (i'e.. MTR = MHW MLW).
30




SPECIAL PUBLICATION NO. 43
is exceeded. In addition, it was found that Savage (1989a, 1989b), and Schmidt and linear interpolation led to results that simply others (1993) consistently used MHW as do not reflect the natural behavior of coastal their vertical reference from which processes. Hence, in 1987, a non-linear nth- volumetric beach changes were measured, order polynomial numerical methodology Komar (1998) used NGVD (it is assumed was introduced and utilized to determine that this is NGVD of 1929, although such is quantitatively open ocean tidal datums for a not stated) but stated that for his site NGVD significant portion of Florida's ocean-fronting "... is approximately equal to mean sea level coasts (Balsillie and others, 1987a, 1987b, ...". Lee and others (1998) used NGVD at a 1987c). Updated results (Balsillie and North Carolina coastal location; they did not others, 1998) are plotted in Figures 1, 2, and state, however, how NGVD departs from 3. MSL at their site. These exemplify instances in which tidal datums referencing
This work is a companion paper to tidal can introduce significantly compounded datums listings for Florida originally error. One illustrates other cases where no published by Balsillie and others (1987a, explanation detailing how tidal datums are 1987b, and 1987c) and updated by Balsillie applied is given, and one cannot be sure if and others (1998). It was determined he or she can have confidence in final necessary to undertake the present results. compilation because of an increasing number
of misapplications of tidal datums appearing To one extent or another, misapplication in the coastal engineering literature. For of tidal datums may be due to a lack of example, Foster (1989, 1991), Foster and understanding as to how they have been
North South
4
-.- 1.5
a 0 0 150 20 25 30 35 0
0 2. I I
0.5
> 0J
Uj r0S7 i
0 0 100 150 200 250 300 350 400 Alongshore Distance (statute miles)
Figure 1. Relationship between open coast dial datums and National Geodetic Vertical Datum of 1929 for the Florida East Coast. Alongshore distance is measured from the center line of St. Mary's Entrance Channel proceeding south to Cape Florida. (Updated in 1992 after Balsillie and others, 1987a).
31




FLORIDA GEOLOGICAL SURVEY
North South
4'
35
5sr
c H
1.5 MHHW.i
3,
- -0.5-2.5 i
-50 0 50 100 150 200 Alongshore Distance (statute miles)
Figure 2. Relationship between open coast tidal datums and National Geodetic Vertical Datum of 1929 for the Florida Lower Gulf Coast. Alongshore distance is measured from north to south with the origin located at the north end of Pinellas County (i.e., north end of Honeymoon Island) and terminating to the south at Caxambas Pass. (Updated in 1992 after Balsillie and others, 1987b). West East
West East
151
3.5
ML r
0.
Q3
CD ____ _S1.5 othrs 197)
. 0.5 L32
>0)M
E -1
-1.5 ..
-2.5
-3
-50 0 50 100 150 200 250 Alongshore Distance (statute miles)
Figure 3. Relationship between open coast tidal datums and National Geodetic Vertical Datum of 1929 for the Northwest Panhandle Gulf Coast of Florida. Alongshore distance is measured from the Florida-Alabama border east to Ochlockonee River Entrance. (Updated after Balsillie and others, 1987c).
32




SPECIAL PUBLICATION NO. 43
established, and what they represent. The 1988, p. 470). Hence, exclusion of inlets first part of this work, therefore, discusses might be an oversight, particularly in view of the history of tidal datums determination and the current inlet management effort definition in U. S. coastal waters. undertaken by the State. At a most basic level, the classification of inlets is well
Guidance illustrating proper tidal datums known depending upon the effect of applications for coastal scientists and astronomical tides relative to volume of engineers is available for important basic fluvial discharge (e.g., van de Kreeke, 1992). tidal datums applications (e.g., Cole, 1983, In fact, for many inlets, selection of the 1991, 1997; Pugh, 1987; Lyles and others, proper datum plane assists in providing a 1988; Brown and others, 1995; Gorman and least equivocal representative design water others, 1998; Stumpf and Haines, 1998). reference level. Hence, a section on inlets For other specific cases it is absent. Verbal as they relate to astronomical tides in Florida communications by a few professionals is herein developed. reach only a small audience. Even then, the
latter often results in a blank stare, leaving WATER LEVEL DATUM PLANES the instructor with the message that the
explanation was not comprehended by the In endeavors concerning hydraulic informant, that he or she has predetermined phenomena with a free fluid surface, many that it is not important, or that the informant practitioners have lost perspective in selection has already predetermined just what is of the reference fluid plane across which force proper. The author has, therefore, in the elements propagate, in both the prototypical latter portion of this work presented a series setting and the natural environment. Given of selected examples and discussion about this assertion, perhaps it would be appropriate tidal datums applications. At the outset, one to review the basics of historical development needs to understand that the surveying of tidal datum plane quantification that has profession, in large part, is concerned with withstood the practicable tests of time. the management of error and variability
associated with horizontal and vertical The first recorded effort of geodetic control. It is often the case that one is not leveling in the United States began in 1856convinced by simple directive that there is a 57. During ensuing years surveying control proper methodology, so evidenced by recent become better. As chronicled by Schomaker improper uses of datum applications in (1981), by the first quarter of this century: coastal engineering works cited above. This
occurs because there isnothing to convince After the previous period of one that the methodology is better or best at comparatively short intervals between reducing error or variability. Therefore, the adjustments, 17 years elapsed before author has opted to present a series of the network was adjusted again. In the common improper tidal datums applications meantime, it had become more and to demonstrate, relative to the proper extensive and complex, and included many more sea-level connections. The
application, just why, numerically, they areGeneral Adjustment of 1929 General Adjustment of 1929
inappropriate. incorporated 75,159 km of leveling in the United States and, for the first time,
INLETS/OUTLE AND 31,565 km of leveling in Canada. The
THE ASTRONOMICAL T77DE U.S. and Canadian networks were connected by 24 ties between Calais,
The preceding definition of open ocean Me./Brunswick, New Brunswick; and tides excludes the influence of inlets (perhaps Blaine Wash./ Colebrook, British more appropriately termed outlets after Carter, Columbia. A fixed elevation of zero
33




FLORIDA GEOLOGICAL SURVEY
was assigned to the points on mean sea Epoch (i.e., the Metonic cycle; shorter series level determined at the following 26 tide are appropriately named, e.g., Monthly Mean stations. Sea Level, etc.). It was not until 1973 that the confusion over the Sea Level Datum or
Father Point, Quebec St. Augustine, Fla. "Mean Sea Level" as it popularly came to be
Halifax, Nova Scotia Cedar Keys, Fla. known and Mean Water Level was resolved
Yarmouth, Nova Scotia Pensacola, Fla. known and Mean Water Level was resolved Portland, Me. Biloxi, Miss. by assigning the more appropriate name of Boston, Mass. Galveston, Tex. "National Geodetic Vertical Datum of 1929"
Perth Amboy, N.J.' San Diego, Calif. (NGVD) to replace "Sea Level Datum of Atlantic City, N.J. San Pedro, Calif. 1929". NGVD of 1929 is additionally
Baltimore, Md. San Francisco, Calif.
Baltimore, Md. San Francisco, Calif. defined (Harris, 1981) as a fixed reference
Annapolis, Md. Fort Stevens, Ore.
Old Point Comfort, Va. Seattle, Wash. adopted as a standard geodetic datum for Norfolk, Va. Anacortes, Wash. elevations determined by leveling. It does Brunswick, Ga. Vancouver, not take into account the changing stands of British Columbia sea level. Because there are many variables Femrnandina, Fla. Prince Rupert, affecting sea level, and because the geodetic British Columbia
Bih Columbia datum represents a best fit over a broad
'There was no tide station at Perth area, the relationship between the geodetic
Amboy, but the elevation of a bench mark at datum and local mean sea level is not Perth Amboy was established by leveling consistent from one location to another in from the tide station at Sandy Hook. either time or space. For this reason NGVD
The 929 adjustment provided should not be confused with mean sea level,
The 1929 adustment provided the
basis for the definition of elevations even though it has always been defined by a
throughout the nationalnetwork asit existed mean sea level (Schomaker, 1981).
in 1929, and the resulting datum is st used
today. The various North American tidal datum planes are defined (e.g., Mariner, 1951;
The elevation adjustment of 1929 was Swanson, 1974; U. S. Department of referred to as the "Sea Level Datum of 1929", Commerce, 1976; Anonymous, 1978; although it commonly became known as the Harris, 1981; Hicks, 1984) as follows: "Mean Sea Level". In coastal work, however,
there are two standard Design Water Levels National Tidal Datum Epoch the specific 19(DWLs) that are applied. These and their year period adopted by the National Ocean definitions (Galvin, 1969) are: Service as the official time segment over which tide observations are taken and reduced
Mean Water Level (MWL) the time-averaged to obtain mean values for tidal datums. It is water level in the presence of waves, and necessary for standardization because of
necessary for standardization because of
periodic and apparent secular trends in sea
Still Water Level (SWL) the time-averaged level. It is reviewed annually for possible water level that would exist if the waves are revision and must be actively considered for stopped but the astronomical tide and storm revision every 25 years. surge are maintained.
Mean Higher High Water (MHHW) the
These water levels (i.e., MWL and SWL) average of the higher high water heights of
appl fo an legthof tme verwhih a average of the higher high water heights of apply for any length of time over which a each tidal day observed over the National field study or experiment is conducted, while Tidal Datum Epoch. Mean Sea Level and other tidal datums are
determined as an average of measurements Mean High Water (MHW) the average of all made over the 19-year National Tidal Datum the high water heights observed over the
34




SPECIAL PUBLICATION NO. 43
National Tidal Datum Epoch. northwest winter winds blow the water away from shore, and 2) water contracts as
Mean Sea Level (MSL) the arithmetic mean it cools. He notes that winds are more of hourly heights observed over the National important in shallow water where tide Tidal Datum Epoch. Shorter series are gauges are located, but that contraction specified in the name; e.g., monthly mean becomes important in deeper waters. sea level and yearly mean sea level. Swanson (1974) also notes *... seasonal changes resulting from changes in direct
Mean Tide Level (MTL) a plane midway barometric pressure, steric levels, river between Mean High Water and Mean Low discharge, and wind affect the monthly Water that may also be calculated as the variability." Cole (1997) notes that seasonal arithmetic mean of Mean High Water and variation in tides is usually attributed to two Mean Low Water. MTL and MSL planes harmonic constitutents: one with a period of approximate each other along the open coast one year termed the solar annual tidal (Swanson, 1974, p. 4). constituent, and the other with a period of six months termed the solar semiannual
Mean Low Water (MWL) the average of all constituent. Some consider these to be the low water heights observed over the meteoroligical in nature, rather than National Tidal Datum Epoch. astronomic. However, because the root cause of cyclic seasonal weather is the
Mean Lower Low Water (MLLW) the changing declination of the sun, they should average of the lower low water heights of more nearly be astronomical in origin. each tidal day observed over the National Harmonic analysis of the annual tidal record Tidal Datum Epoch. can easily determine the amplitude and phase of each of these constituents, thereby
Meanastronomicaltideelevationsexhibit providing a mathematical definition of the cyclic seasonal variability (Marmer, 1951; seasonalvariation. (George M. Cole, personal Swanson, 1974; Harris, 1981) and are communications.) Shorter-term changes included in tide predictions. Marmer (1951) occur bi-weekly and monthly; longer-term notes that seasonal variation in terms of changes occur in the relative levels of land monthly mean sea level for the U. S. can be and sea that are of eustatic or isostatic as much as one foot. Based on the many origins (e.g., Embleton, 1982). It is years of monthly data, researchers (Mariner, apparent, therefore, that there is natural 1951; Harris, 1981) note slight variations in variability associated with any average the seasonal cycle from year-to-year, but representation of tidal datums. Given these also recognize the periodicity in peaks and natural insensitivities associated with troughs over the years. For much of our averages, it is important that we do not coast, lower mean sea levels occur during exacerbate them through improper the winter months and higher mean sea manifestations of our own making when levels during the fall. Harris (1981) applying tidal datums as references. inspected the record to determine if storm
and hurricane occurrence was in any way At this point it is necessary to define responsible for the seasonal change, but certain terms. If one is interested in merely found "... no systematic variability". Galvin referencing a vertical distance without a (1988) reports that seasonal mean sea level requirement of spatial comparability, the changes are not completely understood, but result is termed a mnnst appcation. suggests that there appears to be two That is, the result of the application is good primary causes for lower winter mean tide only for that particular location. If, however, levels for the U. S. east coast: 1) strong in addition to a vertical datum, one has a
35




FLORIDA GEOLOGICAL SURVEY
need that the resulting application will have As an example, suppose that we are spatial comparability (i.e., it can be analyzing and interpreting profile data to compared to the same application at any determine volumetric erosion of sandy other site), the result is a synerbistic beaches and coasts due to extreme event application. We shall discuss this latter class impact. Further, let us select as our reference of application first. water level datum Mean High Water, MHW.
That is, we shall assess erosion volumes
SYNERGISTIC TIDAL above MHW to an upland point that must be
DATUM PLANE APPULICA TIONS carefully deliberated depending upon whether the coast was non-flooded (interpretations are
It has been widely recognized, as normally straightforward) or flooded and/or demonstrated in the introduction to this paper, breached (interpretations can be problematic) that selection of the proper tidal datum as discussed by Balsillie (1985b, 1986). It depends upon the purpose to which it is to be must be recognized that MHW can be applied. The main purpose of this work is to assigned the status of a signature value for a determine the proper tidal datum for use in particular locality, representing its National coastal science and engineering for Tidal Datum Epoch. This assessment can be referencing littoral force and response levied because MHW can change significantly elements. Force elements include from locality-to-locality. For instance, in astronomical tides, storm tides, nearshore Florida MHW varies from +3.12 feet MSL (or currents, waves, etc. Respowme elements +3.36 feet NGVD; Balsillie and others, 1987a) include extreme event beach and coast along the northern portion of Nassau County erosion, foreshore slope changes, long-term on the Atlantic east coast, to +0.66 feet MSL shoreline changes, seasonal shoreline (or +0.90 feet NGVD; Balsillie and others, changes, etc. It became apparent during the 1987c) along the western portionof Franklin course of preparation of this paper that County on the northwestern panhandle Gulf of determination of the proper datum plane is Mexico coast of Florida. This embodies a probably best accomplished by discussing potential maximum difference of almost 2.5 application/use examples. feet in MHW elevation about the State of Florida. Suppose that for the above two
EXTREME EVENT IMPACT areas, profile conditions are comparable.
Furthermore, suppose that extreme events
From the preceding description of tidal embodying precisely the same magnitudes datum planes we must, from the scientific and characteristics producing identical force perspective, be quite careful in selecting a elements impacted the two areas, resulting in reference water level from which we define identical response elements, that is, the same such response elements as beach and coast erosion volumes (i.e., the area above the erosion due to extreme event impact, and dashed lines and below the solid lines of such force elements as the peak combined Figure 4). If, however, we reference the storm tide accompanying extreme events that, erosion volumes to MHW (shaded areas) as in part, induces such erosion. As noted illustrated in Figure 4, 8.12 cubic yards of previously, water level datum planes include sand per foot are eroded above MHW along certain insensitivities regardless of the the northern portion of Amelia Island, 33 per rigorous nature of statistical methods applied, cent less than the 12.05cubic yards of sand It is necessary that we do not further per foot eroded above MHW along western exacerbate these insensitivities, creating St. George Island. It becomes quite clear, additional variability and error through therefore, that erosion volumes around the selection of improper reference datums. state cannot be compared using MHW, since the MHW base elevation is not only
36




SPECIAL PUBLICATION NO. 43
12 ,MHW is not the proper reference
12 water level datum to apply for 10 case A- Nortywn An+1 ht erosion volumes. It also becomes
- Nssau County, M.W = +3.12 ft MSL
S\ Ge =-A12 yd /ft apparent that it is not proper to
6 use the datum for reference for .such a force element as the peak 4 .W4 w combined storm tide. Similar logic results in the conclusion S- MSL that use of the MHHW, MLW,
10 and MLLW datum planes would
SWestern St. George also be improper. It should, in
. Fra kin County, MHW = +0.6 ft MSL fact, be clear that MSL (or MTL) S= -12.05 yd3/ft is the only tidal datum that is to .. .. be used for reference.
S- ML-- LONGER-TERM BEACH
-2 RESPONSES
I I II l l I I I I I I I
120O -1o0 4 0 -40 -20 0 20 40 6 It is clear why the MSL datum
Dist tm "M MW MWWpt (ftt) is the desired convention to apply Fgure 4. Erosion volumes, Q, above MHW for identical for extreme event impacts to which proxies impacted by identlical storm events, but with force and response elements are different local MHW planes. to be referenced. MSL datum should also be applied to longergeographically variable, but significantly so. term force and beach responses. One will note further that, for other North Notwithstanding the need for a standardized American MHW datums (see Table 2), the convention already required for extreme event problem can become even further impact, there is sound reasoning that it applies exaggerated. In fact. it has been to longer-term scenarios, although, such demonstrated that MSL is the best datum application is more subtle than for the extreme from which to reference erosion volumes; event impact case. The preceding extreme "... at the seaward extremity of the post- event impact scenario has dealt with physical storm profile, some material of the seaward beach and coast conditions of a sort which sink (also including some degree of post- transcend certain physiographic limitations. storm beach recovery) may reside above That is, the energetics associated with storms MSL (determined to be about 6% of the and hurricanes so exceed physical stability seaward sink volume from 245 analyzed constraints that individual gradients comprising profile pairs), the analytical method is fairly the beach and coast (e.g., shoreface, unbiased since it is applied equally to all foreshore slope, berm(s), dune or bluff stoss profiles investigated' (Balsillie, 1986). slope; see Figure 5) do not, in themselves, Seaward datums or depth of profile closure impose limiting conditions. Under normal are not suitable references, if only because littoral force conditions, however, survey response is slow compared to the physiographic slope characteristics become response of subaqueous sand-sized more nearly a limiting condition. Perhaps the sediments in the energetic force element surf most important of these gradients is the environment (e.g., Pugh, 1987; Lyles and foreshore slope, a subject that needs some others, 1988). discussion prior to addressing two additional synergistic application/use examples,
It becomes apparent, therefore, that namely, seasonal beach changes and long37




FLORIDA GEOLOGICAL SURVEY
Table 2. Selected North American Datums and Ranges Referenced to MSL (after Harris, 1981).
Station MHHW MHW NGVD MTL MLW MLLW
Eastport, ME 9.32 8.88 -0.20 -0.10 -9.01 -9.41 18.20
Portland, ME 4.87 4.45 -0.22 0.00 -4.46 -4.80 8.91 Boston, MA 5.16 4.72 -0.31 -0.15 -4.86 -5.19 9.58
Newport, RI 2.18 1.93 -0.23 +0.15 -1.69 -1.75 3.62 New London, CN 1.48 1.22 -0.43 -0.10 -1.34 -1.45 2.60
Bridgeport, CN 3.61 3.31 -0.54 -0.05 -3.36 -3.52 6.70
Willets Point, NY 3.85 3.59 -0.58 -0.05 -3.58 -3.78 7.10
New York, NY 2.51 2.19 -0.49 +0.05 -2.29 -2.42 4.50 Sandy Hook, NJ 2.66 2.33 -0.51 0.00 -2.34 -2.47 4.60 Breakwater Harbor, DE 2.46 2.04 -0.41 -0.05 -2.08 -2.15 4.10
Reedy Point, DE 3.07 2.73 -0.35 -0.10 -2.77 -2.85 5.51
Baltimore, MD 0.74 0.51 -0.43 -0.03 -0.52 -0.64 1.03
Washington, DC 1.54 1.39 -0.54 0.00 -1.37 -1.42 2.76 Hampton Roads, VA 1.41 1.22 -0.02 +0.03 -1.22 -1.26 2.44 Wilmington, NC 2.26 2.02 -0.38 +0.02 -2.24 -2.33 4.26 Charleston, SC 1.88 2.87 -0.05 +0.21 -2.67 -2.81 5.17 Savannah River Entr. 3.77 3.38 -0.28 -0.15 -3.66 -3.70 6.94
FLORIDA Listed in Table 1.
Mobile, AL 0.73 0.65 -0.05 -0.05 -0.62 -0.70 1.27
Galveston, TX 0.57 0.47 -0.10 -0.05 -0.44 -0.85 0.91
San Diego, CA 2.90 2.11 -0.21 -0.05 -2.09 -3.06 4.10
Los Angeles, CA 2.63 1.91 -0.08 0.00 -1.87 -2.82 3.80 San Francisco, CA 2.59 2.04 +0.06 +0.30 -1.93 -3.14 4.00 Cresent City, CA 3.22 2.56 -0.12 0.00 -2.49 -3.75 5.10 South Beach, OR 3.22 2.56 -0.49 +0.02 -3.09 -4.48 6.30 Seatle, WA 4.83 3.94 -0.35 0.00 -3.75 -6.48 7.60 NOTES:
MTR = Mean range of tide; average value of MTL is -0.01 feet MSL; average value of NGVD (1929) is -0.29 feet MSL; these stations do not necessarily represent open coast gauging sites.
term beach changes. synonymous with beach face but is commonly more inclusive, containing also The foreshore slope or beach face slope some of the beach profile below the berm (Figure 5) is defined by the Share Protecton which is normally exposed to the action of Manual (U. S. Army, 1984) as "... that part the wave swash." The berm or beach berm of the shore lying between the crest of the is the "... nearly horizontal part of the beach seaward berm (or upper limit of wave wash or backshore formed by the deposit of at high tide) and ordinary low water mark, material by wave action ... some beaches that is ordinarily traversed by the uprush and have no berms, others have one or several" backwash of waves as tides rise and fall." (U. S. Army, 1984). The berm and Komar (1976) elaborates further, stating that foreshore (or beach face) are separated at the foreshore slope "... is often nearly the berm crest or berm edge.
38




SPECIAL PUBLICATION NO. 43
Coast Gre
Neershtre sane
S defines area of neorumote currents
Coat Ueech oc shore a
Cckshore fafnw Inshore or Shore foce _Offshe or (extends through breaker toneil Beach
bluff F0ce
or
escerpMen t Berms
eech rp et rBreaker#
Ordinaryr %waw watevele
plunge pnlot
Figure 5. Beach proflle-slated terms (from U. S. Army, 1984).
In Florida, the foreshore slope is defined The slope of the foreshore tends to (Chapter 16B-33, Florida Administrative increase with an increase in the grain size of Code, State of Florida) as: the sediment ( U. S. Army, 1933; Bascom, 1951; King, 1972). Dubois (1972) found an ... that portion of the beach or coast inverse relationship between grain size and
that is, on a daily basis, subject to the foreshore slope where the foreshore combined influence of high and low sediments contain appreciable quantities of tides, and wave activity including wave heavy minerals. Sediment porosity and
uprush or backwash. For purposes of permeability effects on the foreshore are
this Chapter, it includes that part of the discussed by Savage (1958).
beach between mean higher high water (MHHW) and mean lower low water
(MULW). Generally, foreshore slope increases with an increase in nearshore wave energy (all
The slope of the foreshore, the steepest other factors held constant), and an inverse portion of the beach profile, is a useful design relationship is found when wave steepness is parameter since along with the berm elevation applied (e.g., Bascom, 1951; Rector, 1954; it determines beach width (U. S. Army, 1984, King, 1972). For instance, steeper eroding p. 4-86). As a response, element the waves such as winter waves will result in foreshore is a function of force elements such flatter foreshore slopes, while longer (less as astronomical tides, waves, currents, and steep) accretionary waves such as postproperty elements such as grain size, storm or summer waves produce steeper sediment porosity, and sediment mass slopes. Average foreshore slope statistics density. for Florida are listed in Table 3. While this treatment of foreshore slopes is general, it
39




FLORIDA GEOLOGICAL SURVEY
Table 3. Flodrida Foreshore Slope Statistics by County and Survey.
.... I Average Standard County Survey Type Survey Date n Average Standard I I I I Slope Deviation
FLORIDA EAST COAST
Nassau Control Line Feb 1974 81 0.0359 0.0235 Nassau Control Line Sep-Oct 1981 85 0.0474 0.0344 Duval Control Line Mar 1974 68 0.0199 0.0178 St. Johns Control Line Aug-Sep 1972 203 0.0523 0.0322 St. Johns Control Line Feb-May 1984 210 0.0339 0.0384 Flagler Control Line Jul-Aug 1972 99 0.1077 0.0273 Volusia Control Line Apr-Jun 1972 227 0.0348 0.0306 Brevard Control Line Sep-Nov 1972 217 0.0798 0.0413 Brevard Control Line Aug 1985-Mar 1986 219 0.0719 0.0347 Indian River Control Line Nov 1972 116 0.1163 0.0335 Indian River Control Line 1986 119 0.1201 0.0793 St. Lucie Control Line Jun 1972 115 0.1012 0.0358 St. Lucie Condition Jan-Feb 1983 36 0.0919 0.0248 Martin Control Line Oct-Nov 1971 115 0.0939 0.0378 Martin Control Line Jan-Feb 1976 96 0.0867 0.0287 Martin Control Line Feb-Apr 1982 104 0.0845 0.0301 Palm Beach Control Line Nov 1974-Jan 1975 226 0.1011 0.0347 Palm Beach Condition Aug 1978 24 0.1113 0.0334 Broward Control Line 1976-1976 127 0.1099 0.0423 Dade Condition Nov 1985-Feb 1986 28 0.1243 0.0328 Total n and Weighted Averages 2,515 0.0760 0.0359
FLORIDA LOWER GULF COAST
Pinellas Control Line Sep-Oct 1974 185 0.0747 0.0447 Manatee Control Line Aug 1974 67 0.1009 0.0419 Manatee Control Line Aug 1986 67 0.0942 0.0377 Sarasota Control Line Jun-Aug 1974 181 0.0983 0.0375 Sarasota Condition Apr 1985 62 0.1051 0.0469 Charlotte Control Line May 1974 67 0.0757 0.0343 Charlotte Control Line Dec 1982 68 0.1127 0.0363 Lee Control Line Feb 1974 238 0.0843 0.0415 Lee Control Line May-Sep 1982 236 0.0980 0.0419 Collier Control Line Mar-Apr 1973 144 0.0796 0.0265 Collier Condition Sep 1984 40 0.0927 0.0277 Total n and Weighted Averages 1,355 0.0903 0.0389
FLORIDA NORTHWEST PANHANDLE COAST
Franklin Control Line May-Jul 1973 147 0.0933 0.0349 Franklin Control Line Jun-Sep 1981 244 0.1155 0.0472 Franklin Condition Oct 1982 31 0.0769 0.0322 Gulf Control Line Jul-Sep 1973 161 0.1032 0.0540 Gulf Condition Jan 1983 45 0.0785 0.0327 Bay Control Line Feb 1971-Feb 1973 141 0.0707 0.0255 Walton Control Line Oct 1973 130 0.0991 0.0699 Walton Control Line May 1981 130 0.1060 0.0578 Okaloosa Control Line Nov-Dec 1973 49 0.0650 0.0406 Escambia Control Line Jan-Feb 1974 213 0.0988 0.0429 Total n and Weighted Averages 1,219 0.0970 0.0458
Grand Total n and Weighted Average 5,089 0.0848 0.0391 NOTE: n = number of profiles per survey.
40




SPECIAL PUBLICATION NO. 43
will suffice for the following use/application Balsillie, 1998). Here, however, beach width examples. is used since, compared to the others, it offers the largest range in magnitudes. Seasonal Beach Changes
Let us investigate such seasonal changes Beach changes due to extreme impacts for two localities with identical profile from storms and hurricanes are considered to conditions and average seasonal MSL more nearly represent isolated events. There shoreline variations, but different MHW are, however, beach changes that are more datums. First, however, we need some nearly episodic or cyclic. For instance, representative foreshore slope data. From systematic beach changes through an Table 3, let us select the average foreshore astronomical tidal cycle (e.g., Strahler, 1964; slope of tan afs = 0.085 to represent a Sonu and Russell, 1966; Schwartz, 1967), winter foreshore slope and a maximum of cut and fill associated with spring and neap tan afs = 0.2 (.e., 0.085 + 3 standard tides (e.g., Shepard and LaFond, 1940; deviations) to represent a summer foreshore Inman and Filloux, 1960), and effects of sea slope. The two cases, each with a summer breeze (e.g., Inman and Filloux, 1960; and winter profile are illustrated in Figure 6. Pritchett, 1976), are well known. Of the possible cyclic occurrences, however, Like Figure 4, Figure 6 is a simplification, perhaps the most pronounced
is that occurring on the
I I I T V I I f I I I l l
seasonal scale. Using the .. above prescribed rules, the +4 following scenarios can be +2: SMAMER / suggested. During the winter a a = o us season, when incident storm -2 wave activity is most active, 4 high, steep waves result in +4 e6.9 shoreline recession. Normally, the berm is eroded and a +2
0W IN T ER .' MS t. gentle foreshore slope is 2 tan a = 0.0 5 produced. Sand removed C from the beach is stored ; 4 MHW+t5. MSLC t offshore in one or more MS longshore bars. During the arm summerseasonsmallerwaves j +4 low with smaller wave steepness +2 SUMMER values transport the sand 0l tan a. .2 stored in longshore bars back 2 -4: 67.1 ft.I onshore, resulting in a wider beach berm and steeper gem/ foreshore. +2 WINTE us
0 tan af = 0.0 85Seasonal beach changes -2
have been described in terms 4 CASE 40 ft. of sand volume changes, MHW = +4.0 ft. MSL contour elevation changes, 12 so 4o ' -40 -6o and horizontal shoreline shift Distance (feet) or beach width changes (see Figure 6. Seasonal hodrizontal shorerne shift analysis.
41




FLORIDA GEOLOGICAL SURVEY
albeit representative since the slopes and offer the opportunity for calculation of distances presented are precise. First, let us volumetric changes which, if sufficient focus our attention on the CASE I locality alongshore profiles are surveyed, allows for where MHW = +2.5 feet MSL. One will sediment budget determinations. see that if we utilize MSL as the reference
datum, the seasonal variability in beach Profile surveying for temporal beach width shifts by 40 feet. If, however, one changes, however, requires a monument uses MHW as the reference datum, the shift system maintained over many years. For is 56.9 feet. The two values depart from instance, Florida's coastal monument system each other by 30 per cent. If, on one hand, has been in place for some 26 years. Other the CASE I locality were to be singularly such efforts occur on a site-specific basis. For assessed using the MHW reference plane most of our coasts there is insufficient shoreline, consistent results would emerge. monumentation, or it has not been in place for If, on the other hand, one would wish to enough time to assure long-term records. relate force elements (e.g., wave and tide Even the 26 years for the Florida program is characteristics) to the shoreline response, not lengthy. Moreover, early surveys the use of MHW would pose problems (more measured shoreline positions. In order to about this later). obtain volumetrics from shoreline position data, horizontal shoreline change (AX) and
Similar assessment for the CASE II volumetric change (AV) have been related in locality (MHW = + 4.0 feet MSL) results in the Sham Pmtecdon Maual (U. S. Army, a departure of the MHW MSL shoreline 1984) according to: change of 40 per cent. As for CASE I,
application results similarly apply. AX= cAV
Now let us compare the results of where c is a relating coefficient. If not very shoreline shift at the two localities. MSL carefully applied, such an approach can shoreline shifts would remain comparable produce highly misleading results (Balsillie, from locale to locale, since they directly 1993a). represent both the tide base and surf base.
MHW shoreline shifts, however, depart from Long-term shoreline change rate data for each other by 15 per cent. Again, as with Florida (Balsillie and Moore, 1985; Balsillie, extreme event impact, MHW shoreline shifts 1985f, 1985g; Balsillie, and others, 1986) can not be compared from locality to locality are determined from shoreline position data (the same would hold true for other datums for the period from about 1850 to present. such as MHHW, MLW, MLLW, etc.). In fact, Commonly up to about a dozen data points if we evaluated seasonal beach changes are available from which to conduct temporal volumetrically, MHW or any of the other site- analyses. specific variable datums would result in
precisely the same non-comparability By way of example, let us inspect the problems of the extreme event example application of MHW as the reference datum previously given, plane for determination of horizontal shoreline change. Let us select an average
Long-Term Beach Changes MHW value of + 1.7 feet MSL and a maximum value for MHW of + 3.0 feet MSL,
Long-term beach changes pose some both of which are representative of Florida highly important concerns. Profile type conditions (from Table 1). Using these data, surveys provide a source of detailed coast, three cases of combinations of MHW and beach, and nearshore conditions. Such data foreshore slope values are illustrated in
42




SPECIAL PUBLICATION NO. 43
Figure 7. Additional data could have been selected
as well as additional 3 CASE 1
2 Bermtanaf, = 0.085 combinations; however, 2 Len,- =1.7 .t the three illustrated 1 cases will more than
o0- us (SURF RASE)
suffice for our purposes.
.1 <102 f
The profiles of the three examples are plotted so that the MSL (Surf Base) 2 MHW +1.7 ft intercepts define the .- CASE 2 origins of the plots that tI '- te = 0.2
0 *MLt (SURF BASE) they may be compared. 1 .Horizontal differences of MHW intercept locations
are identified by vertical
dashed lines. Deviations f range from 10.2 to 25.6 2 feet, all of which are significant illustrating the CA 3 ML (SU ) inappropriate nature of tm. = 0.os s using MHW for such a
purpose. Again, as with extreme event impact
and seasonal shoreline -4 -I change, MHW shoreline .40 .s 10 0 30o so a So shifts are not comparable MaUrn sr S BASE SSaer (feet) from locality to locality
(the same would hold Figure 7. Long-term shoreine shift analysis. true for other datums
such as MHHW, MLW, MLLW, etc.). In fact, processes. if we evaluated long-term beach changes volumetrically, MHW or any of the other site THE SURF BASE specific extremal variable datums would result in precisely the same non- The preceding application/use examples, comparability problems of the extreme event while rigorously identifying inconsistencies and seasonal shoreline shift examples resulting from the use of extreme datum previously given. planes for coastal science and engineering purposes, have not specifically addressed We can approach the subject from a coastal processes in terms of the forces that different perspective. If MSL is not used as cause beach responses. a reference Surf Base plane, then what should be used? If one selects an extreme In order to understand how the samrf base tidal datum plane such as MHW, does it applies, one needs a basic understanding of represent a base to which aktological force how wave statistics are derived and applied. and response elements can be based? Does At a given water depth a wave train is a it have spatial continuity? Is it applied in a near-periodic set of waves with a conceptually correct sense? All of these characteristic average wave crest height H, questions need be directed toward coastal wave length L, period T, and having a
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FLORIDA GEOLOGICAL SURVEY
specific direction of propagation. Where tide might be considered to be maintained, water depths are such that waves remain say, for 1/2 to 1 hour. Doubling this value, relatively stable, the wave record (such as since two highs occur in each tidal day for that measured by a wave gauge) will the semidurnal tide, then MHW is actually represent all wave trains (i.e., multiple trains) maintained for about 4 to 8 per cent of the passing the gauge. Multiple wave train time (e.g., 14 and 28 days a year). height and period measurements are termed Superimposed upon MHW is the significant the special wave record or wave field,. wave height which, by definition, neglects Shot -breaking waves, however, do not 70 per cent of the wave record (assuming conform to spectral wave statistics. This that Hs adequately includes any significant occurs because in nearshore waters, waves zero wave energy component; Balsillie, are ultimately limited by water depth 1993b). Clearly, such an application would according to db = 1.28 Hb (McCowan, be inappropriate for one applying such force 1894; Balsillie, 1983a; Balsillie, 1999b; elements to annual or long-term conditions. Balsillie and Tanner, 1999) where Hb is the Unfortunately, however, such misapplicawave crest height at shore-breaking and db tions, of which this is just one example, are is the water depth where the wave breaks. commonplace. On the other hand, such an Hence, shore-breaking waves engender application might have more viable moment wave statistics for sn wave application if it included a storm surge (i.e., trains since a wave train with larger waves peak combined storm tide minus the will break further offshore than one with astronomical tide) to represent the peak smaller waves, combined storm tide and attendant wave activity which occurred coincident with the
It follows, then, that moment wave peak astronomical tide. This latter case, statistics vary depending upon whether they however, has application only to identify a represent the spectral wave record or single conservative design elevation for a structure shore-breaking wave trains. The most (e.g., perhaps a pier) which is a monergistic commonly applied nearshore wave height tidal datums application, but certainly not to statistics are the average wave height H, profile response which constitutes a root-mean-square wave height Hrms, synergistic application. significant wave height Hs (average of the
highest 30 per cent waves of record), H10 Previously discussed use/application (average of the highest 10 per cent waves examples have already led to the elimination ofrecord), and H1 (average of the highest 1 of extreme datum planes (i.e., MHHW, per cent waves). Each of these moment MWH, MLW, MLLW) as has the preceding measures is applied in the design of coastal example, and MSL and NGVD remain for engineering solutions by defined prescription, consideration. The NGVD reference is not, Relating moment measures for spectral and of course, a tidal datum. It is rather, for all shore-breaking wave cases are listed in Table practical purposes a geodetic datum for 4 to illustrate the variability of relating computational reference, that although for coefficients. open-coast gauges has a departure generally less than 0.5 of a foot from MSL for Florida,
Let us look at an example of tide the long-term primary departure of MSL and conditions to which we might superimpose NGVD is subject to influences of sea level certain wave conditions. Figure 8 illustrates rise or fall (shorter-term natural deviations 6 days of an astronomical tide record. have been discussed above). Hence, it Suppose one inspects the case where MHW should not be utilized as a datum, and Hs are, for whatever reason(s), selected particularly where global data are involved for use. From the plots, each peak of the (i.e., where the non-tidal vertical reference
44




SPECIAL PUBLICATION NO. 43
Table 4. Moment Wave Height Statistical Relationships (after Balsime and Carter, 1984a, 1984b).
Portion of Wave Record Spectral Relationships Shore-Breaking Relationships
Considered
All Waves A rage Wave Average Breaker Hei4ht = H Height = Hb
All Waves H= 0. 885 H H = 0.98 H,
Highest 30% H= 0. 625 H Hb = 0. 813 H,,
Highest 10% H= 0.493 /140 H = 0, 73 /Ho
Highest 1% H= 0.375 -4 H = 0. 637 /4,
Definitions:
Average Wave Root-MeaN-Square Wave
N N H,= significant Height = H= H Height = H.= -N I/ wave heght
NOTE: Formulas apply to both H and Hb; H,, H10, and H1 are calculated using the form of the equation as for the average wave height.
represents a conceptual plane not located Therefore, by the process of and/or not calculated such that it is not elimination MSL is defined as the surf base necessarily comparable to NGVD). The (it is also the tide base, not to be confused remaining tidal datum is, then, MSL. Other with the concept of the wave base). Upon than its identification by elimination of other inspection of Figures 1, 2, and 3, it is readily datums, there are strong motivating reasons apparent that MSL, like the other datums, why MSL is the proper tidal datum reference has variability. Why, then, would we select to use when dealing with coastal processes it as a convention for reference? Water (i.e., force and response elements). As we levels are not globally coincident in the have already learned, principal force vertical sense for very real reasons. elements include astronomical tides, storm However, MSL is a measure representative tides, and waves. Astronomical tides are, by of the entire distribution of the metonic definition, already accounted for when using astronomical tide, and is the only one of the MSL, and storm tides are extreme events tidal datums that has statistical continuity though accounted for as described in the and comparability of results from place to preceding section. Waves, however, place. Noting that for open coastal waters constitute an ubiquitous phenomenon near MSL is equivalent to MTL (Swanson, 1974, constant in nearshore coastal waters (except p.4), then the MTL measure remains to for coasts with a substantial zero wave represent the central tendency of the tide energy component), distribution since metonic measures of highs and lows are used in its determination. The
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FLORIDA GEOLOGICAL SURVEY
one should view it in the .... .statistical sense where we know S..more about its central tendency 2 than we do about the behavior of the lower foreshore (corresponding to MLW or MLLW) or higher foreshore (corresponding to MHW or MHHW). When we approach the extremes of the 4 -slope, exceptions due to physiographic irregularities can occur. Hence, one needs to view the surf base foreshore slope intersection as a focal point about which the foreshore rotates. In this context, the focal point is directly related to incoming force elements. Furthermore, it is conceptually not subject to variations to which the upper and lower parts of the foreshore are subject, since it is an origin both common and comparable to the focal point at other localities.
From a slightly different viewpoint, one argument
Figure 8. Semidiumal tide curves for 6 tidal days (from proffered by a colleague who Manner, 1951). took the "devil's advocate' position, is that the MHW intercept represents the most issue becomes particularly poignant from stable portion of the foreshore slope. While inspection of Figure 1 where the behavior of this may appear appropriate to the layman, low waters (i.e., MLW and MLLW) and high from the geological perspective it is not. It waters (i.e., MHW and MHHW) are anything is, in fact, the least stable in terms of but symmetrical in their relationship to MSL representing a normal slope. The most (or MTL), signifying a need for an average stable position of the foreshore is probably at surf base measure. Statistically extreme the MSL intercept (i.e., relative to other average point measures providing numerical submerged portions of the profile) since it is values of upper (i.e., MHW and MHHW) and reflective of average, ongoing force elements lower (i.e., MLW and MLLW) tidal datums to which it is modified as a response are robustly founded. Corresponding element. By comparison, the foreshore in extremes of such physiographic features as the vicinity of the MHW or MHHW intercepts the foreshore may not be so robustly is affected only during high tide stages and founded, since its formation and can be reflective of extremal impacts (e.g., maintenance has not been rigorously defined storm wave events). Extreme impacts in terms of forces and responses (e.g., Kraus affecting the MHW foreshore are likely to and others, 1991, p. 3). Given the manner result in relict features which persist until in which we currently define the foreshore, continual average force conditions finally
46




SPECIAL PUBLICATION NO. 43
return the upper portions of the slope to plane that is relevant to the surf base. For a normal slope status. relatively short experiment or field study, MWL or SWL references are suitable to
What point estimator of wave represent the time frame of the experiment parameters, representing the appropriate or study. Such referenced results, however, force element, does one subscribe for an may not be comparable to results referenced extreme average measure of the to MSL at other localities. For this reason, astronomical tide, say for MHW? One does all applicable datums ... MSL, MWL, and not apply such point estimators for wave SWL, where known ... collectively termed transformation synergistic applications, Design Water Levels (DWLs), should be because none would be appropriate. Hence, provided in documentation of results. unless an average sea level (MSL or MTL) is
combined with an average wave height, one SEA LEVEL RISE is mixing "apples and oranges". It is
imperative when undertaking such a task, So far, we have but in passing we render the task to simplest terms. For mentioned the effects of sea level rise, instance, when transforming waves to the recalling that the primary difference between point of shore-breaking, including any wave NGVD and MSL (or MTL) is sea level rise. In reformation and rebreaking, the waves an historical context, the effect of sea level should be expressed as an average wave rise on the current metonic period has, thus height or, perhaps, root-mean-square wave far, been insignificant from a surveying height since these measures include all perspective. Its future effect, however, waves of record. Do not use the significant remains controversial (e.g., Titus and Barth wave height, average of the highest 10 per (1984) and Titus (1987) versus Michaels cent of heights, average of the highest 1 per (1992), to mention but only several cent of wave heights, etc. Whether or not a published works among a vast number on significant zero wave energy component is the subject). Other work indicates details of included depends on the purpose of the work sea level reversals or pulses (Tanner, 1992, (Balsillie, 1993b). Any conversion of the 1993), also characterized as crescendos average wave height to extreme wave height (Fairbridge, 1989). measures of Table 4, say for design
purposes, is accomplished by converting the There are certain applications where average measure, but only after wave temporal specifications of sea level rise are transformation as an average height has of potential consequence. Hence, from a occurred. Kraus and others (1991) note the data management and processing viewpoint, importance of the average wave height and it becomes in certain cases necessary to tout its use to be the "... "Rosetta stone' start with NGVD and calculate the relative for conversion ...", no less important is the date-certain sea level rise component. The proper application of the surf base (MSL) result, of course, becomes the date-certain which becomes the Rosetta Stone for MSL (or MTL). For the 1960-1978 National referencing tide and wave phenomena. Tidal Datum Epoch, the following relationship Another good reason for using averages assessed in British Imperial units is posited: throughout any numerical transformation
process is because one is often unable to MSL0 = NGVD + c (D 1969.5) determine from published results if the
transformation methodology is truly where MSLo is the date-certain value for commutative. MSL (or MTL), c = 0.0060 for Florida's east Coast), c = 0.0064 for Florida's Lower Gulf
MSL is, therefore, the only datum Coast, and c = 0.0069 for the Florida
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FLORIDA GEOLOGICAL SURVEY
Panhandle Gulf Coast (Balsillie and others, combined storm tide (super-elevated water 1987a, 1987b, and 1987c, respectively), level including contributions of wind stress, and D is the survey date. Please note that barometricpressure decrease, dynamic wave the value of c changes with time and setup and astronomical tides) corresponding location; the current value of c for a to a 50-year return period elevation is particular coast is a representative regression normally used for design calculations. value. Superimposed upon the storm tide still water level is a design wave height, normally a
MONERGIS77TIC TIDAL DATUM breaking wave height corresponding to Hb 10
PLANE APPLICA TIONS or Hbl. As previously noted, where a wave shore-breaks is dependent on the water
Thus far, the above application/use depth which, in turn, is dependent on patexamples have been described as syner- terns of sediment redistribution occurring gistic. That is, horizontal shoreline shift and during event impact. Sediment redistribution volumetric change results are referenced to is largely a function of offshore sediment a datum so that they can be compared transport and longshore bar formation spatially within a North American or global (Balsillie, 1982a, 1982b, 1983a, 1983b, context. The scientific need to do so has 1983c, 1984a, 1984b, 1984c, 1985a, been robustly demonstrated. Even more, 1985b, 1985c, 1985d, 1985e, 1986; considerable analytical work is required to Balsillie and Carter, 1984a, 1984b, etc.). An determine such synergistic results which example is illustrated in Figure 9. cannot be simply recalculated to another
datum. Such design work calculations are site-specific because results will be
As described in the introduction there influenced by the pre-impact site-specific are, however, other quite different concep- profile configuration. There is no intention, tual applications of astronomical tidal datum nor at this time a need to compare such planes. Some of these are not necessarily results to other localities. Should such an bound by the need for a spatial tidal datum application need arise (e.g., a generalized convention. These are described as modeling effort or an accounting need to monergistic applications. The purpose, here, assure consistency in design application(s)), is to demonstrate several such examples. then the reference base should be MSL.
However, such transformations to other
DESIGN SOFFIT ELEVATION datums can be easily accomplished, CALCULATIONS compared to much more involved recalculation of synergistic data (i.e., volumes
"Soffit elevation" is a generic term or horizontal distances). meaning the elevation to the underside of the
lowest supporting structural member exclud- EROSION DEPTHISCOUR CALCULATIONS ing the piling foundation, say, for a pier or
single- or muti-family dwelling. Such Site-specific design work such as elevations are calculated for extreme minimum pile embedment requires elevations associated with the impact of knowledge of the design surface elevation. extreme events (i.e., storms and hurricanes). This elevation necessarily includes erosion The goal is to raise the structure to an depth (e.g., longshore bar trough elevation or elevation so that it is above the destructive beach erosion elevation), additional scour hydraulic force elements which will pass caused by the pile, and sediment below the soffit and through the piling liquefaction. In essence these design foundation. For a pier, for instance, a peak elevation calculations are treated in the same manner as design soffit elevation
48




-- SPECIAL PUBLICATION NO. 43
am- Setiond Destroyed Section
40 section
40
0 Hbl
20 FLAGLER BEACH PIER
w 0
t -. ST SWL
0 Bar ough Envelope-' "
-200 -100 0 100 200 300 400 500 600
Distance from NGVD Shoreline (feet)
Figure 9. Actual damage to the Flagler Beach Pier from the Thanksgiving Holiday Storm of 1984 (Balsillie., 1985c) used to test the Multiple Shore-Breaking Wave Transformation Computer Model for predicting wave behavior, longshore bar formation, and beach/coast erosion (after Balsillie. 1985b).
calculations. intersection of the rising shore and the elevation of 150 percent of the local mean
SEASONAL HIGH WATER CALCULATIONS tidal range above local mean high water ...
(para. 161.053(6)(a)1,F. S.). That is:
In addtion to short-term erosive
impacts due to extreme events, our coasts SHW = ( 1.5 MRT ) + MHW are subject to long-term changes. In 1972,
the State of Florida incorporated
consideration of storm/hurricane erosion in in which MRT is the mean range of tide affixing the location of Coastal Construction (commonly referred to as the mean tide Setback Lines. In 1978, it adopted a posture range). One might assume that the 30-year in which quantitative extreme event erosion erosion projection is to be assessed at the became the primary means by which Coastal SHW elevation. This is simply not true and, Construction Control Lines were located. It in fact, as we have seen earlier would be a was not until 1984, however, that long-term misapplication leading to spatial discontinuity erosion was officially recognized by the introducing computational error (Balsillie and State of Florida (Balsillie and Moore, 1985; Moore, 1985). Rather, the erosion Balsillie, State of Florida (Balsillie and Moore, projection needs to be assessed at MSL. 1985; Balsillie,1985f; 1985g; Balsillie and The required methodology specified by rule others, 1986; etc.,). In 1985, the Growth (para. 16B-33.024(3)(h), F. A. C., Management Amendment required republished as State of Florida, 1992, 62Bassessment of erosion at any coastal site for 33.024(3)(h)1., F. A. C.) specifies NGVD as which a permit application was tendered to the assessment elevation. The original rule, be assessed for a 30-year period, however, was written before compilation of Associated with 30-year long-term erosion datum elevations, foreshore slope, and sea projections is the local SeasonalHigh Water level rise information for the State. (SHWI) defined as ... the line formed by the Subsequent work (Balsillie, Carlen, and
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-- FLORIDA GEOLOGICAL SURVEY
Watters, 1987a, 1987b, 1987c) has remedied from the figures that only the upper east the situation, and the rule needs to be coast is significantly affected by the SHW, reassessed. Following is an alternative for attesting to the low impact figure of Curtis consideration. and others (1985).
BEACH-COAST NICKPOINT ELEVATION BOUNDARY OF PUBLIC VERSUS PRIVATE PROPERTY OWNERSHIP
In reality, Seasonal High Water is a
misnomer. First, the components necessary The boundary between private (i.e., for computation are metonically derived (i.e., upland) and public (i.e., seaward) beach 19-year averages). Second, the results have ownership is normally fixed by some not been demonstrated to represent seasonal commonly applied tidal datum, For most of variation in astronomical tide behavior, the U. S. this boundary is determined by the Third, it has been demonstrated that upon plane of MHW which when it intersects the application, only about 13% to 15% of beach or coast forms the line of mean high undeveloped beach property in Florida would water. However, unlike other riparian be affected by the SHW application (Curtis ownership determinations (i.e., fluvial, and others, 1985). lacustrine and estuarine), littoral properties must, in addition, contend with significant An alternative consideration for such wave activity that seasonally varies. Hence, an application, and others, is the ocean-fronting beaches all too often beach/coast nickpoint elevation. The experience cyclic seasonal width changes of nickpoint represents the point where the a magnitude long recognized as problematic beach intersects the coast, normally in affixing an equitable boundary (Nunez, identified as the base of a dune or bluff. 1966; Johnson, 1971; O'Brien, 1982; Generation and maintenance of the nickpoint Graber and Thompson, 1985; Collins and is primarily a function of direct extreme McGrath, 1989). event impact. These
elevations for Florida are
probabilistically -co.. |- each near.ore investigated; the results
are plotted in Figure 10. N* Median (i.e., 50th
percentile) nickpoint usL elevations, N., for Florida or Mu
are as follows: 1) East
Coast: +7.15 feet NGVD ZNo -42+5.9 (1929), 2) Lower Gulf 10 EAST-COAST Coast: +5.65 feet NGVD t
(1929), and 3) Panhandle 0 .
Gulf Coast: +6.45 feet 10 LOWER GULF COAST 3.7+ NGVD (1929). . .
0
The relationship 0 N* -4.3 + 4.3 P
between nickpoint 110 PANHANDLE GULF COAST
betee n 10aelevations and SHW A k elevations for Florida is 0 1 0!2 0.3 0. 4 0.5s 0.S 0.7 0.8 0.9 1.0 illustrated in Figures 11, Exc dnce Prob ty. P 12, and 13. It is apparent Figure 10. Beach/coast nickpoint elevations for Florida.
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SPECIAL PUBLICATION NO. 43
*4.
BREVARD
SHW
10
. 3
UJ Mi an No
00 . . .., I I
0 100 200 300 400 On. (miS)
Figure 11. Comparison of Seasonal High Water (SHW) and Medan Beach/Coast Nckpoint Bevation (NJ) for the Florida East Coast.
10
Meinm N,
0 100 200
Distc (m )
Figure 12. Comparison of Seasonal High Water (SHW) and Medan Beach/Coast Nickpoint BElevation
(N.) for the Florida Lower Gulf Coast.
.Ne
a g MYGUP FRAWKUN UU
10
z"Me.an N,
0 100 20 Distance (i*e)
Figure 13. Comparison of Seasonal High Water (SHW) and Medan Beach/Coast Nickpoint Bevation (Ne) for the orioda
Panhandle Gulf Coast.
51




. FLORIDA GEOLOGICAL SURVEY
Many investigators have suggested Florida case and adopt the that the legal boundary for ocean-fronting "winter and most landward line beaches should not be continuously moving of mean high tide" as the legal with the seasonal changes, but should be boundary between public the most landward or "winter" line of mean tidelands and private uplands ... high water (Nunez, 1966). Selection of the (it should be understood that "winter" MHW line would be the most such a boundary, whichrelatively stable, would not be permanently
practical to locate and would be the most fixed but would be ambulatory to protective of public interest by maintaining the extent there occurs long-term maximum public access to the shore (Collins accretion or erosion). and McGrath, 1989).
The use of the MHW datum plane for
In Florida, the ocean-fronting legal the determination of a boundary is boundary seasonal fluctuation issue was straightforwardly a monergistic application; deliberated upon in State of Florida, one must be careful, however, to note that Department of Natural Resources vs Ocean determination of the seasonal shoreline shift Hotel, Inc. (State of Florida, 1974) as it related (or beach width) is not. This will require a to locating the MHW line from which a 50-foot synergistic application using MSL. Similarly, setback was to be required. Judge J. R. Knott any periodic review and boundary relocation rendered the following decision: due to long-term shoreline changes will require the synergistic approach.
This court therefore concludes
that the winter and most INLES AND ASSOCIATED
landward mean high water line ASTRONOMICAL 7DES
must be selected as the boundary between the state and
the upland owner. In so doing It has been speculated that tidal inlets the court has had to balance the can significantly affect the character of open public policy favoring private coast tide behavior. There are, however, littoral ownership against the insufficient alongshore data crossing inlets, public policy of holding the both upcoast and downcoast, upon which to tideland in trust for the people, assess the effect of inlets (termed the where the preservation of a vital "shadow effect"). In addition, flow public right is secured with but characteristics vary from inlet to inlet and a minimal effect upon the interests multitude of such investigations would be of the upland owner. required to investigate the alongshore influence of inlets. There are, however, some A 1966 Caifornia Court of Appeals isolated open coast tide data near inlets or decision rejected the application of a .
decision rejected the application a within inlet throats close to the shoreline. continuously moving boundary in Peole vs There are more data interior to inlets. Such Kent Estate. However, no decision has been information for 24 Florida tidal inlets and
rendered as to what line to use (Collins and McGrath, 1989). More recently, Collins and passes are plotted in Figure 14 from which
some significant elucidating conclusions may McGrath (1989) report: be gleaned.
The Attorney Genere/'s Office in
he Attorney General's Office i The data of Figure 14 are displayed in
California has offered its informal
California has offered its informal terms of the measured inlet tide data minus
opinion that, if squarely faced
with the issue, California courts the open coast tide data of Balsillie and others would follow the reasoning in the (1987a, 1987b, 1987c). In this way the
52




SPECIAL PUBLICATION NO. 43
0.4 -,- reference plane for a synergistic o.2 application (e.g., storm impact,
--------------------- seasonal, or long-term beach
a..-_ _* __ changes), the amount of error
-0.2 . introduced is potentially highly
-0.4 significant. It would, in addition, -0. occur over a quite short segment of
* ** shoreline. For MHW .0.8 39% of the data are acceptable (i.e., -1.o MHW lie with 0.1 ft. of the open coast 1.2 data) with 61% of the data being SOA - unacceptable. For MLW 76% of the
M data are unacceptable. However, for
S.2 MTL MTL almost 70% of the data are a o *.r r - acceptable. This shift in data
-0.2 * acceptability for MTL is not aberrant.
4 *Rather, it is to be a moderating
* expectation since MTL is the plane 0.8 lying halfway between MHW and .s MLW ** MLW and should, therefore much 00. 6 more closely approach open coast
S* . MTL values than any of the other
. *-*- ** -extremal tidal datum planes.
S0- . Therefore, depending on the
-0.2. application, the locally measured -0.4 MSL (MTL) datum plane or the open
-.4 coast MSL (MTL) datum plane should
o0 0s 1.0 1 2 2. be used for synergistic applications in the vicinity of inlets (which is used
fts ftrm Shor flO should be clearly specified). Hence,
Figure 14. Departure of Flordda inlet tide data and MTL (or the MSL surf base) is, once open coast tide data (measured tide data from DNR, again, the proper datum plane to use Bureau of Survey and Mapping). See text for for inlets. In fact, O'Brien (1931) discussion. intentionally included in his definitions for tidal characteristics
acceptability of the data within the dashed (e.g., flow area, tidal prism) that they be lines (i.e., plus and minus 0.1 ft.) can be referenced specifically to MSL. easily assessed. Data for MHHW and MLLW Ideally, the alongshore "shadow plot similar to MHW and MLW data with effect" of inlets on astronomical tides should somewhat greater variability, and are not be quantitatively assessed. Such work is, shown. however, expensive and time consuming and is not expected to be forthcoming any time
The first conclusion to be drawn from soon. Figure 14, is that the amplitude of the tide is attenuated by the inlet (i.e., MHW becomes It is also of significance to note that lower in elevation and MLW gains elevation); Cole (1997, p. 38) has found that nth order this is illustrated in a different manner for polynomial equations precisely determine two Florida inlets in Figure 15. Hence, if one tidal datums within estuaries. The order of were (as before) to use MHW as the the best fit polynomial for an estuary was
53




FLORIDA GEOLOGICAL SURVEY
OCm DE T t s a FT PIECE litf TIDE RAIGE &W ST- LUE MET 2.00 i F- ---------- ----I
I I
o
I II I
/ -itO-- I I
I II.
1.__ A- --- -,
/ I : I '
- 2.00 .. .i .. .. 6 .. . 00
Tirne (Hours)
4' I ,
Figure 15. Open ocean and inside astronomical tides for Ft. Pierce
and St. Lucie Inlets, Florida (fom Anonymous, 1992).
found to be predictable based on the length ACKNOWLEDGMENTS-of the estuary and the travel speed of the tidal wave within the estuary. Review of this work by selected staff
v I I I
-2.00 . ..-...... ... .. .... I, I .. .. ... I, *.... '
0 00 10 00 20.00 30.00 40.00T 50.00 60.00 70.00 Time (Hours)
Figure 15. Open mcan and inside asfronomucal tidles for Ft. Pierce
and St. Lucde Inlets, Floida (from Anonymous, 1992).
found to be predictable based on the length ,ACKNVOWLEDGEMENTS of the estuary and the travel speed of the tidal wave within the estuary. Review of this work by selected staff
of the Florida Geological Survey is gratefully CONCLUSIONS acknowledged, in particular those editorial contributions of Jacqueline M. Lloyd, A considerable amount of information, Thomas M. Scott, Kenneth M. Campbell, Jon hopefully simplified as much as possible, has Arthur and Walter Schmidt. Review by the been presented in the above application/use Bureau of Beaches and Coastal Systems is examples. It would not serve further purpose also acknowledged with special thanks to to restate conclusions here that could be more Ralph R. Clark and Thomas M. Watters for succinctly touted, other than to state that MSL their interest in the subject and/or editorial (or open-coast MTL) is the proper datum to comments. Special thanks are extended to employ for synergistic coastal engineering George M. Cole who reviewed the applications. It is hoped that this work has manuscript and encouraged its publication. rendered it apparent that how we perceive and treat such subject matter in a scientific context REFERENCES is sensitively critical. The considerations presented herein embody not just philosophy, Anonymous, 1978, Definitions of surveying but engender intellectual contemplation and and associated terms: Joint deliberation necessary to arrive at a deductive, committee of the American Congress reasonable, and robustly correct convention on Surveying and Mapping and the for application. In this day and age, it is American Society of Civil Engineers, unfortunate that while we are finally realizing 210 p. such enhanced data processing capabilities, we are fraught with misapplication that all-too- 1992, St. Lucie Inlet manageoften render good data to inaccurate results. ment plan: Applied Technology and Management, Inc., Gainesville, FL.
54




SPECIAL PUBLICATION NO. 43
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FLORIDA GEOLOGICAL SURVEY
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56




SPECIAL PUBLICATION NO. 43
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FLORIDA GEOLOGICAL SURVEY
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, 1989b, Methods for analysis of 1971, The significance of
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Mobility, Florida State University, p. 26-31.
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Galvin, C. J., Jr., 1969, Breaker travel and 570 p.
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WW2, p. 175-200. N.J., Prentice-Hall, 429 p.
, 1988, The annual tide in 1998, Wave erosion of a
Chesapeake Bay: in C. J. Galvin, ed., massive artificial coastal landslide: Coastal Engineer Notes, p. 3-4. Earth Surface Processes and Landforms, v. 23, p. 415-428.
Gorman, L., Morang, A., and Larson, R.,
1998, Monitoring the coastal Kraus, N. C., Larson, M., and Kriebel, D. L., environment; Part IV: mapping, 1991, Evaluation of beach erosion shoreline changes, and bathymetric and accretion predictors: Coastal
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1985, The issues and problems of the beach-nearshore profile at Duck, defining property boundaries on tidal North Carolina, USA, 1981-1991: waters in California: California's Marine Geology, v. 148, p. 163-177.
Battered Coast, Proceedings of a
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Harris, D. L., 1981, Tides and tidal datums Administration, National Ocean
in the United States: U. S. Army, Service, 182 p.
Corps of Engineers, Coastal
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Hicks, S. D., 1984, Tide and current Publication No. 135, 142 p.
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McCowan, J., 1894, On the highest wave Schomaker, M. C., 1981, Geodetic Leveling:
of permanent type: Philosophical U. S. Department of Commerce, Magazine, Series no. 5, v. 32, p. National Oceanic and Atmospheric 351-358. Administration, National Ocean Survey, NOAA Manual NOS NGS 3.
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Stumpf, R. P., and Haines, J. W., 1998, U. S. Department of Commerce, 1976,
Variations in tidal level in the Gulf of Manual of tide observations: Coastal Mexico and implications for tidal and Geodetic Survey Publication 30wetlands: Estuarine, Coastal and 1, 72 p.
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2 vols, 1272 p.
60

PAGE 1

"StateofRorida DepartmentofEnvironmental Protection DavidB.Struhs,Secretary Division ofAdministrative and Technical Services Rorida Geological SurveyWalter Schmidt,State Geologist and ChiefPublished fortheRoridaGeological SurveyTaUahassee, Rorida1999

PAGE 3

LETTEROF TRANSMITTAL Florida Geological Survey Tallahassee Governor Jeb Bush Florida Department of Environmental Protection Tallahassee, Florida 32304 Dear Governor Bush: The Florida Geological Survey, Division of Administrative and Technical Services, Department of Environmental Protection is publishing two papers: "Seasonal variationinsandy beach shoreline position and beach width" and "Open-ocean water level datum planes: Use and misuseincoastal applications". The first paper identifies a methodology for predicting seasonal shifts in Florida's shorelines. A number of practical uses emerge from the research, two of which are the analytical assessment of long-term shoreline erosion data, and determination of the seaward boundary of public versus private ownership. The second paperisa companion paper to "Open-ocean water datum planes for monumented coasts of Florida" published by the Florida Geological Survey as a separate work. It identifies erroneous applications made when considering mean sea level (MSL), mean high water (MHW), mean low water (MLW), etc., tidal datum planes, illustrating why they are erroneous using practical examples, and details how proper applications shouldbedetermined. Walter Schmidt, Ph.D., P.G. State Geologist and Chief Florida Geological Surveyiii

PAGE 5

CONTENTSPageSEASONAL VARIATIONINSANDY BEACH SHORELIN E POSITION AND BEACHWIDTH ABSTRACT 1 INTRODUCTION .......................................................1SEASONAL VARIABILITY 2 DATA AND RESULTS 3 Data 3 Results ........................................................7 DISCUSSION 9 The Single Extreme Event and the Combined Storm Season 9 Beach Sediments11Astronomicalndes..............................................14APPLICATIONOFRESULTS15General Knowledge16Seaward BoundaryofPublicversusPrivate Ownership ..................,6 Long-Term Shoreline Changes ...................................17 Project Design and Performance Assessment 19 CONCLUDING REMARKS...........................................20ACKNOWLEDGEMENTS20REFERENCES.....................................................20LISTOFFIGURESFigure 1. Relationship between seasonal shoreline variability, V$'and mean rangeoftide, hINt. .4Figure2.Monthly time seriesforTorrey Pines Beach, California,forshoreline variability, V; breaker height, HIl, and wave period, T. 5 Figure 3. Monthly time seriesforStinson Beach, California, for shoreline variability, V; breaker height, HIl, and wave period, T 5 Figure4.Monthly time seriesforJupiter Beach, Rorida,forshoreline variability,V;breaker height, HIl, and wave period, T. 6 Figure 5. Monthly time seriesforGleneden Beach, Oregon, for shoreline variability, V; breaker height, HIl, and wave period, T. 6 Figure 6. Illustrationofmathematicalfitforequation (1). 9 Figure7.Illustrationofmathematicalfitforequation (2). 9 Figure 8. Exampleofthe quick response and recoveryofthe beachtostormwaveactivity, Pensacola Beach, Rorida, December1974..'0Figure 9. Monthly average occurrencesofextreme event wave eventsforthe Outer BanksofNorth Carolina. ........................................,1v

PAGE 6

Figure10.Typical examplesoftimeseries relationofmonthlydataforbreaker height,waveperiod, and foreshore slope grain sizeforCalifornia andnorthwesternFlorida panhandle. .'3Figure11.Monthlyvariation in sea levelforthecontiguous United States. .16Figure12.Exampleoflong-term shoreline change rate temporal analysis using seasonal shorelineshiftdata. .'8LISTOFTABLES Table 1. Force, response, and property elementsforseasonal shorelineshiftanalysis...4 Table2.Assessmentofthewavesteepness ratiofora selectionofexpressions relatedtoVS.8 Table3.Mean annual beach grain size (foreshore slope samples)frommonthlydata, and range in size. 12 Table4.Twocasesofsedimentologic responseofmomentmeasurestowaveenergy levels. 12 Table5.Seasonal range inmonthlyaveragewaterlevels15APPENDIX APPENDIX: PROPAGATION OFERRORSIN COMPUTING28OPEN-OCEAN WATER LEVELDATUMPLANES:USEAND MISUSE IN COASTAL APPLICATIONSABSTRACT29INTRODUCTION29INLETS/OUTLETSANDTHE ASTRONOMICAL TIDE 33WATER LEVELDATUMPLANES33SYNERGISTICTIDALDATUMPLANE APPLICATIONS36EXTREME EVENT IMPACT36LONGER-TERM BEACH RESPONSES37Seasonal Beach Changes41Long-Term Beach Changes42THE SURF BASE43SEA LEVELRISE47MONERGISTICTIDALDATUMPLANE APPLICATIONS48DESIGN SOFFIT ELEVATION CALCULATIONS48EROSION DEPTH/SCOUR CALCULATIONS49SEASONAL HIGH WATER CALCULATIONS49BEACHCOAST NICKPOINT ELEVATION50BOUNDARY OF PUBLIC VERSUS PRIVATE PROPERTY OWNERSHIP50INLETSANDASSOCIATED ASTRONOMICAL TIDES52CONCLUSIONS54ACKNOWLEDGEMENTS54REFERENCES54vi

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LISTOFFIGURESFigure1.Relationship between open coast tidal datumsandNational Geodetic Vertical Datum for the Florida EastCoast.............................31Figure2.Relationship between open coast tidal datumsandNational Geodetic Vertical Datum for the Florida Lower GulfCoast........................32Figure3.Relationship between open coast tidal datumsandNational Geodetic Vertical Datum for the Northwest Panhandle Gulf Coast ofFlorida..........32Figure4.Erosion volumes,Qe'aboveMHWfor identical profiles impacted by identical storm events, but with different localMHWplanes...............37Figure5.Beach profile-related terms. .....................................39Figure6.Seasonal horizontal shorelineshiftanalysis41Figure7.Longterm shoreline shift analysis43Figure8.Semidiurnal tide curves for 6 tidal days46Figure9.Actual damage to the Flagler Beach Pier from the Thanksgiving Holiday Storm of 1984 (Balsillie, 1985c) usedtotest the MUltiple ShoreBreakingWaveTransformation Computer Model for predicting wave behavior, longshore bar formation, and beach/coast erosion ......................49Figure10.Beach/Coast nickpoint elevations for Florida .......................50Figure11.Comparison of Seasonal High Water(SHW)andMedian Beach/Coast Nickpoint Elevation(NJfor the Florida East Coast51Figure12.Comparison of Seasonal High Water(SHW)andMedian Beach/Coast Nickpoint Elevation(Ne ) for the Florida Lower Gulf Coast51Figure13.Comparison of Seasonal High Water(SHW)andMedian Beach/Coast Nickpoint Elevation(Ne>for the Florida Panhandle GulfCoast.............51Figure14.Departure of Florida inlet tide data and open coast tidedata...........53Figure15.Open oceanandinside astronomical tides forFt.Pierce and St. Lucie Inlets54LISTOFTABLES Table1.Tidal DatumsandRanges for Open Coast Gauges of Coastal Florida. .....30Table2.Selected North American Datums and Ranges ReferencedtoMSL ........38Table3.Florida Foreshore Slope StatisticsbyCountyandSurvey40Table4.Moment Wave Height Statistical Relationships45vii

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SPECIAL PUBLICAliONNO.43SEASONAL VARIATION INSANDYBEACH SHORELINE POSITION AND BEACH WIDTHbyJames H. Balsillie,P.G.No.167ABSTRACTAnnual cyclic fluctuationsinbeach width due to seasonal variability of forcing elements(e.g.,wave energy) havebeena subjectofconcerted interest for decades.Seasonalvariabilitycanbeused to1)identifyandevaluate the accuracyofhistorical, long-term shoreline data interpretations,2)aidinthe identificationofthe boundaryofsovereignversusprivate land ownership,and3) predict expected seasonal behaviorofbeachnourishment projects, which shouldbea stated up-front design anticipation.Inthis paper, data representing monthly averagesareusedtocomparewinterandsummer wave heightandwave steepnessasthey relate to seasonal shoreline shifts. Coupled with astronomical tide conditionsandbeach sediment size,twoquantifying relationshipsareproposed for predicting seasonal shiftofshoreline position(i.e.,beach width). INTRODucnON Theconfigurationofthebeach in profileviewis primarily duetotidalfluctuationswhichcause periodic changes in sea level,andshore-breakingwaveactivity.Anychangeinwavecharacteristicsanddirectionofapproachwill,depending ontidalstage,resultina change inthesandybeachconfiguration.Systematicbeach changesthrougha singleastronomicaltidalcyclearewellnoted(Strahler,1964;Otvos,1965;Sonu and Russell,1966;Schwartz,1967).Cycliccutandfillassociatedwithspring and neaptides(ShepardandLaFond,1940;Inmanand Filloux,1960),andtheeffectofsuchphenomena as sea breeze (Inman and Filloux,1960;Pritchett,1976),cancontributeadditionalmodifyinginfluences. Beach changes are notedtooccurattimeintervalslongerthana tidalcycle(e.g.,Dolan andothers,1974),Smaller beach cusps.forexample,mayrangefrom10to50metersapart,whilesinuousformsmay1spandistancesoffrom450to700meters,andsuchfeaturesoftenmigrate alongshoreattimescales ontheorderofdaysorweeks(Morisawaand King,1974).Asthebaybetweencusphorns passes a profile line,thebeach becomesnarrower,and as a horn passes,thebeachwidens.Apredictionmodelfordailyshoreline change has been suggestedbyKatoh and Yanagishima(1988).Ofthepossiblecyclicchanges, perhapsthemostpronounced isthatoccurring ontheseasonal scale. Duringthewinter"season,whenincidentstormwaveactivityismostactive,high,steepwavesresult in shoreline recession. Generally,theberm is heightenedwitha gentleforeshoreslope, although erosion scarpsmayform.Sand removedfromthe beachisdepositedoffshorein oneormoresubmergedlongshore bars. During thesummer"seasonlowerwaveswithsmallerwavesteepness valuestransportsandstoredoffshorebackonshore, resulting in awiderbeach.Itshould be notedthatalongsomecoasts such astheapproximatelyeast-west

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FLORIDA GEOLOGICAL SURVEYtrending coastlineofLong Island, New York (Bokuniewicz,1981;Zimmerman and Bokuniewicz,1987;Bokuniewicz and Schubel,1987),no seasonal variability canbedetected(H.J. Bokuniewicz,J.R.Allen, personal communications). Such lackofseasonal variabilitymaybe symptomaticofsub-seasonalstormwavegroups combinedwithanalmost imperceptible climatic change (J.R.Allen, personal communications), possibly exacerbated by changes in oceanicstormfrontazimuths relative to shoreline azimuths (Dolan and others,1988).Similarly, theeastwesttrending shorelineofthe northwestern panhandle coastofFlorida, while having annual net longshore transporttothewest,appearstobe characterized by dailytoweeklyrather than seasonal reversals in longshore current direction (Balsillie,1975).Itappears, therefore,thateast-westtrendingshorelinespose considerations deservingfurtherattention. However,formuchofthe Earth's open, ocean-fronting shoreline seasonal changes are clear,whichconstitutes the subjectofthis paper.SEASONALVARIABIUTYClassically, seasonal variability is associatedwithCalifornia beaches wheretheirgeometric character changes noticeablyfrom"summerto"winter"(e.g.,Shepard and LaFond,1940;Shepard,1950;Bascom,1951,1980;Trask,1956,1959;Trask and Johnson,1955;Trask and Snow,1961;Johnson,1971;Nordstrom and Inman,1975;Aubrey,1979;O'Brien,1982;Thompson,1987;Patterson,1988;Collins and McGrath,1989).A considerable numberofsuch studies have also been conducted along the U.S.east coast(e.g.,Darling,1964;Dolan,1965;Urban and Galvin,1969;DeWall and Richter,1977;DeWall,1977;Everts and others,1980;Bokuniewicz,1981;Miller,1983;Zimmerman and Bokuniewicz, 1987). Geometric characteristicsofseasonal2change have been described in terms of sand volume changes (Ziegler and Tuttle,1961;Dolan1965;Eliot and Clarke,1982;Aubrey and others,1976;Davis,1976;DeWall and Richter,1977;DeWall1977;Thorn and Bowman,1980;Everts and others,1980;Bokuniewicz,1981;Miller,1983;Zimmerman andBokuniewicz,1987;Samsuddin and Suchindan, 1987), bycontour elevlltionchanges (Shepard and LaFond,1940;Ziegler and Tuttle,1961;Gorsline,1966;Urban and Galvin,1969;Nordstrom and Inman,1975;Aubrey,1979;Felder and Fisher,1980;Clarke and Eliot,1983;Berrigan,1985;Brampton and Beven,1989),and in termsof botizontalshoTelineshilts or beach width changes (Darling,1964;Johnson,1971;DeWall and Richter,1977;DeWall,1977;Aguilar-Tunan and Komar,1978;Everts and others,1980;Clarke and Eliot,1983;Miller,1983;Garrow,1984;Berrigan and Johnson,1985;Patterson,1988;Kadib and Ryan,1989).Potential legal ramificationsofseasonal shoreline changes astheyrelatetothe jurisdictional shoreline boundary position have been addressedbyJohnson (1971), Hull (1978), O'Brien (1982), and Collins and McGrath (1989). While there are other seasonal shoreline change applications (discussed in the section on ApplicationofResults), the motivationforthisworkcenters about derivationofa least equivocal methodologyforidentifying probable realshiftsin historical long-term shoreline change.Inaddition towaveheight andwavesteepness, wave direction and beach sediment characteristics can influence the degreeofseasonal beach change. Wave directionisparticularly influentialforpocket beaches found along the U.S.westcoast. Along some beaches(e.g.,Oceanside BeachjustnorthofCapeMeares, Oregon) a sandy "summer" beachisremoved during the"winter"season exposing a cobble beach.Insuch cases, "summer"to"winter"grain

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SPECIAL PUBLICATION NO.43size differences are significant.Inthis study, however,weshall dealwithrelatively straight, ocean-fronting beaches composed entirelyof material.DATAANDRESULTSInaninvestigationofseasonal beach changesatTorrey Pines Beach, California, Aubrey and others (1976) state: NNo field studies to date have been able to adequatelyquantifythese wave-related sedimentredistributions.In approaching a quantitative solution(s)tothe problem,itbecomes prudenttoidentifythe force and response elements involved. Basic force elements are identifiedtobe:1)astro nomical tides, 2)waveheight, and 3)wavesteepness. Response elements are: 1) vol ume change, 2) change in beach elevation, or 3) horizontal shoreline shift. While the beach sediment mightbeviewedasa response element, given the paucityofinformation about temporal/spatial sediment variationasitimpacts this problem,itmaybeprudenttotreat sediment characteristics (within the sand-sized range)asa property element (see section on Beach Sedimentsforfurtherdiscussion). The response element used here is the horizontal shoreline shift. Fortunately,weare dealingwitha measurewhich,comparedtothe others, has the largest range in possible values. For example, vertical contour changes are less than1-1/2to2 meters, and volumetric changeswouldbe3to4 times less than horizontalshift(" rule-of-thumb" guidance suggestedbyU.S.Army(1984)and Everts and others (1980)). while horizontalshiftmay range uptotensofmeters. Data While the amountofdata availabletoquantifyseasonal variationinshoreline positionisnotlarge,14data setsforwhichsufficient information appears to exist were3located to searchfora solution (Table 1). First. it mightbereasonable toinspecttherelationshipbetweenastronomical tidal conditions and horizontal seasonal shoreline shift, V5'since the tidal condition essentially constitutes a signature characteristicforeach site(i.e.,itcan vary considerably depending on the coast under study). Horizontal seasonal shorelineshiftisdefinedasV5=V max -Vmin,where V max isthe largest measurement representing thewidestseasonal beach, and Vminis smallest measurement representing the narrowest beach (in this paper Visthe distancefroman arbitrary permanent coastal monument to the shorelineatanyonetime). The mean rangeoftide, hmn,(i.e.,the difference between meanlowwaterand mean high water), is plotted against Vs in Figure1.While thereisscatter in the plot, a general trend is apparent. In additiontoastronomical tide conditions,weknowthatwaveclimate mustbeconsidered andthatit, like tidal conditions, varieswidelyfromcoasttocoast. Selectionofvaluesforvariables given in Table 1 canbeillustrated using time series plotsofmonthly averagesforshoreline shift andwavedata.AnexampleforTorreyPinesBeach, California, is plotted in Figure 2, which representstwoyearsofconcurrently observed monthly averagesforshoreline position, wave height,waveperiod, and sediment data (Nordstrom and Inman,1975;Pawka and others,1976).Further, the data have been smoothed by a threepointmovingaveragingsequence.Comparisonofhorizontal shoreline shifts and wave heights suggeststhatforthe monthsfromabout December through April stormwaveactivity prevailed, resulting in a narrower beach,withlull conditionsfromaboutMaythrough October coincidingwithbeach widening. Hence. the average storm wave height, Hs ,isthatoccurringfromDecember through April, and the average lullwaveheight, HL ,isthatoccurringfromMay

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FLORIDA GEOLOGICAL SURVEYTable 1. Force,response,and propertyelementsforseasonalshoreline shift analysis.Site VsHs Hl Ts TLhm..0 CO/COs (m) (m)(m)(5) (5)m(mm)Gleneden,OR46.9 1.14 0.729.28.1 1.910.350.815Stinson Beach, CA42.71.280.9916.1 12.1 1.210.301.370Atlantic City. NJ32.01.040.777.47.01.400.300.820Torrey Pines, CA29.01.340.9911.811.41.280.280.794Goleta Point.CA22.91.070.7312.514.01.280.210.547Duck.,NC(1982)18.61.100.758.88.11.000.400.808(1983)20.41.260.739.28.10.980.400.749(1984)17.41.150.708.78.40.960.400.654Surfside-Sunset,CA20.11.100.7310.213.21.070.260.398Huntington Beach,CA18.31.140.9911.610.41.150.211.078Holden Beach, NC15.20.70 0.506.57.01.300.300.614Jupiter Beach.FL10.71.000.635.45.50.920.420.614Boca Raton.FL2.40.640.514.94.50.840.900.933Hollywood,FL2.10.49 0.474.74.50.790.601.037Vs=Seasonal range in shoreline positionorbeachwidth;H s=Storm season averagewaveheight; HL=Lull season averagewaveheight; Ts=Storm season averagewaveperiod; Tl=Lull season average wave period; hmn=Mean rangeoftide; D=Swash zone mean grain size; ll =Lull seasonwavesteepness; Is =Storm seasonwavesteepness; CA=California.FL=Florida,NC=North Carolina. NJ=NewJersey,OR=Oregon. Sourcesofdataaregivenby beach in thetext.4shorelineinclusive) consistently result in the 43-meter seasonal shorelineshiftreported by Johnson (1971) and O'Brien(1982).Concurrently observed dataforfouryears at Jupiter Beach, Florida (DeWall,1977;DeWall and Richter,1977)are plotted in Figure 4. ItisapparentfromFigure 4thatlull wave heightsoccurfromaboutMaythrough September resulting in awiderbeach,withstorm waves occurringfromabout October through at least JanuaryVs=21.9+37.6limnr=0.1302 6O_,.....,,.............-.,........""'T"""T"""'T"'""T"""".,..-_,.....,,....,.......-.,.....,....,..""'1 (m) 20hmrt (m)Figure1.Relationshipbetweenseasonalvariability, Vs ,andmeanrange oftide,h mrt .through October. Note thatwaveperiod varieslittlethroughout the yearforthis site. The classic exampleofseasonalshorelineshift(Johnson,1971;O'Brien, 1982)forStinson Beach, California. represents a22-yearperiod(1948-1970),suggestinganaverage shorelineshiftofabout43meters annually. These data are plotted against six yearsofwavedataforthe period1968to1973(Schnieder and Weggel,1982)in Figure 3. Sediment data arefroma separate source (Szuwalski, 1970). Notethatunlike the data plotted in Figure 2,waveperiodshowsa concerted seasonal trend. The inferencemaybemade. therefore,thatspecial attention shouldbegiven to seasonalwavesteepness values. More recent shoreline surveys published by Collins and McGrath(1989)forthree years(1984-1986

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SPECIAL PUBLICATION NO.4311TI0 JFMAMJJASONOJ MOfttll Figure3.Monthly time seriesforStinson Beach, California,forshoreline variability, V; breaker height, H b ; andwaveperiod,T.waveheight and period are given by HL ,and TlI respectively; similarly,stormseason variables are givenbyHs ,and Ts .Wave heights and periodswereselected to represent conditionsforthelead flanksofseasonal accretion/recession trends, sinceitis under these force element conditionsthatresponses are produced. Similar analyseswereconductedforBoca Raton andHollywoodBeaches in Florida (DeWall,1977;DeWall and Richter,1977)forfour yearsofmonthlydataforV,waveheight and period,withmean grain sizesforswash zone sediment. Data publishedforHolden Beach, North Carolina (Miller,1983)wereplotted by the original author sothatseasonal changes5 IS90 10 85 V 10 ",.;........"'"75 ,. ', ,,.(m) V, 70 .\ .,' \ tiS -,,.,\. 60 ,,(m),.I,,55 ,. I50 "' \ /. - '\IH b.5 /' --- 0 .. 35 (m) I.. I.JH b1.2(m) 1.l 1.00.9 MJJASONOJFMAMtlcMllIIRgure 2.Monthly time series for Torrey Pines Beach, California,forshoreline variability, V; breaker height, Hb ,andwaveperiod, T.producing anarrowerbeach.Monthlyaveragesforwaveheights and periodswereconcurrently measured,witha reported representative grain size.TA single yearofmonthly wave datawerecollected (Aguilar-Tunan and Komar,1978)atGleneden Beach, Oregon,fromwhicha seasonal shorelineshiftofabout47meters is evident. Because wave data reported by the authors are probably inappropriate(i.e.,theystrongly appeartorepresent the initial offshore breakingwaveheight), the multi-year data reportedbythe U.S.Army(1984)are used. A singleswashzonesedimentsizewasreported by Aguilar Tunan and Komar(1978).Shorelineshiftand wave data are plotted in Figure 5. Thesefourexamples illustratehowwavedata valuesweredeterminedtorepresent each season, where the lull season

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v (m) (m)T(I)withsimultaneously measured seasonalwavedata. Sediment data arefromtheU.S.Army(1984).Perhaps themostcomplete data sets areforDuck, North Carolina,atthe Coastal Engineering ResearchCenter'sField Research Facility. All information necessaryforthisstudywascollected simultaneouslytoresult in dataforthree years (Miller,1984;Miller and others,1986a,1986b,1986c).JF M A M JJ A SON0J IIoIItll Figure5.Monthlytimeseries for Gleneden Beach, Oregon, for shoreline variability,V;breaker height, Hb ;andwaveperiod, T.Where the specific studies discussed above did not provide the necessary astronomical tide information, these datawereobtainedfromother sources (Harris, For a4-1/2year period, Patterson(1988)reports aVsof20.1 metersforSurfside-Sunset Beach, Orange County, California, alongwithseasonalwaveinformation. Sediment grain size informationisfromSzuwalski(1970).6TResultsforGoleta and Huntington Beaches, California (Ingle,1966)includeapproximatelymonthlysurveysfora one year period, including beach profiles,wave,and sediment data. Unfortunately,waveinformationforthese sites representsonlythose conditionsforthe day profilesweresurveyed. While informationforthese sites generallywasconsistent,waveperiod datafromSchneider and Weggel(1982)wereusedforGoleta Beach duetounresolvable dispersion in thefewdaily data.(I) Month Figure4.Monthly time series forJupiterBeach, Florida, for shore variability,V;breaker height, Hb ;andwaveperiod, T.vcouldbedirectlyassessed by measuring peaksofchange. The data representfouryearsofapproximatelymonthlyprofilesfor16alongshore profiles,withconcurrently measuredwavedata. Sediment data arefromthe U. S.Army(1984).(m)(m)FLORIDA GEOLOGICAL SURVEYSeasonal shorelineshiftdataforAtlanticCity,NewJersey (Darling,1964)weremeasuredforatwo-yearperiod along

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SPECIAL PUBLICAliONNO.431981;U. S.Departmentof Commerce,1987a,1987b).ItisworthwhiletonotethatBerrigan and Johnson(1985)comparedwavepowercomputationstoshoreline positionforseven yearsofdataatfourlocalities along Ocean Beach, San Francisco, California. Deepwaterwavedataweremeasuredatsites rangingfrom3.9to26.7kilometers offshore (Berrigan,1985).While some refractioneffectsmayhave occurred duetothe San Francisco entrance bar, there appearstobea correlationbetweenan increase inwavepowerand decrease in beachwidth.ResultsThere is,fromFigure 1,anindicationthatastronomical tides play a role in seasonal variability. The mean rangeoftide, h mrt and seasonalwaveheight difference, ,;" H s H L ,mightbeexpressedasa sum,i.e.,hmrt+ orasa product,i.e.,hmrt Sinceenergyaccordingtoclassicalwavetheoryis proportional.tothe height squared, theproduct,i.e.,hmrt mightbemore appropriate. On the other hand, the sum hasmeritbecause laboratory data,ifavailable, could be used (i.e., since tides are almost never modelled in laboratory studies, a productwouldbe meaningless because the resultwouldalwaysbezero). Ineitherevent,manycombinationsofparameterswereinvestigated (Balsillie,1987b;see also Table 2forsomeoftheequations), anditwasfoundthatthesumwasnot nearly as successfulastheproduct;eitherscatterwasexcessiveasindicatedbyalowcorrelationcoefficient,r,and/orthefittedregression line didnotpassthroughthe originofthe plot.Manyresearchers have emphasized the importanceofwavesteepness in influencing the shore-normal directionofsand transport(e.g.,Johnson,1949;Ippen and Eagleson,1955;Saville,1957;Dean,1973;Sunamura and Horikawa,1974;Hattori andKawamata,1980;Sawaragi and7Deguchi,1980;Watanabe and others,1980;Quick and Har,1985;Kinose and others,1988;Larson and Kraus,1988;and Seymour and Castel,1988).In this paper, the "summer" or lull seasonwavesteepness is expressedas >L = H/(g T L2),and the"winter"orstormseason steepnessas CPs = HJ(g Ts2),Itbecame apparentthatincorporationofthewavesteepness ratioinducednumericalconsistencyinquantitative prediction.Whetherthe ratioisevaluatedas >/>s or >JCPL becomes important. Theformofthe ratioforvarious arrangementsofrelating expressionsforassessment purposes is given in Table2.Hence,if (>/>s) <1.0thenwaveheight during thestormseasonmustbemore important;if (>/>s) >1.0thenwavesteepness plays astrongerrole. Infact,itwouldbeexpectedthat >L/>S results inbettercorrelation, since beaches are erodedbysteeperwaves,withlowersteepnesswavesresulting in accretion. Inaddition,beachsedimentcharacteristics have beentoutedtoplay a significant role. The generalviewisthat,holding force elementsconstant,a beach composedofcoarser sediment is more stable than a beach composedoffinermaterial(e.g.,Krumbein andJames,1965;James,1974,1975;Hobson,1977),i.e.,a beach comprisedofcoarser sediment should exhibit less seasonal variability than a beach composedoffiner sediment (notethatthis explanation isnotsostraightforward,andwillbeaddressed in greater detail in thefollowingsection). Since a numberofinvestigatorshave published general quantifying relationshipswhichin additiontowaveheight and steepness, incorporate sand size(e.g.,Dean,1973;Hattori and Kawamata,1980;Sawaragi and Deguchi,1980;Watanabe and others,1980),itwouldbeprudenttoconsider granulometry in this study. Again,itistobe notedthatmanyformsofpossible relating parameterswere

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FLORIDA GEOLOGICAL SURVEY Expressions Using CPL/CPS r Expressions Using CPS/CPL r h"",+41 L {4I sl0.9339 hmrt + 4Is/4IJ 0.7445 [hmrt + (AH)14lL/4lS 0.8843 [hmrt + (AH)] 0.4071 h"",(AH)4l L f4l s0.9047 hmlf(AH) 0.5498 h"", + 4l L /4l s1 hIM + 4ls/4l,J D0.8567D0.3837 hIM(11H)4l L /4l S hIM(liH) D0.9672D0.5478r= Pearson product-moment correlation coefficient between each expression evaluated using measured force and property element dataofTable 1, and measured Vsresponse dataofTable 1.Table2.Assessmentofthewavesteepnessratio for a selection of expressions relatedtoVconsidered in an earlier study,butthatonlythemostsuccessful are presented here. Incorporating the preceding considerations,twoequations are presented, thefirstwhichincludesforceelements only,whichposits:(1)and isplottedin Figure 6. The cubic least squares regressioncoefficient(forced through the origin)of78.5isin unitsofmlwherethemean rangeoftide, hmn,and seasonalwaveheight difference, are in meters. The standard deviationofthe datafromtheequation (1) regression line in the vertical direction (Ricker,1973)is11.4m. The second equation includes the meanswashzone grain size,0,toyield:(2)plotted in Figure7,wherein all variables are expressed in consistent units. Intermsofdimensions, onewillnotethatwhenall dimensional cancellations are made in equations (1) and (2), length only remains. Thecoefficientof0.025wasdetermined using the samefittingprocedure asforequation (1).Itis apparentfromthe figuresthatequation (2) reduces someofthescatterofequation (1). The standard error (Ricker,1973)ofequation (2) in the vertical direction is6.8m.Itmayalsobeofinteresttonotethatthecoefficientofequation (1)whenexpressed relativetothecoefficientof8

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__._-_..9 TheSingle Extreme Eventand theCombinedStonnSeason become availabletofurthertestand/or enhance the prediction relationships. Nevertheless, the results presented here are statistically valid; one should notbetimid in applying resulting computational values pending future refinement in prediction methodology.Onepurposeofthis paper istoactasa pleaformore data. Following are discussionsofafewconcerns relatedtoseasonal shoreline variation predictions. The sandy littoral zone is comprised,fromoffshoreto-onshore,ofthe nearshore, the beach, and the coast. Eachofthese three subzones is created and maintained by setsofforce elements normallydifferentfromeach otherwithinthe long-term temporal framework. When astormor hurricane impacts the littoral zone, the following scenarios are possible: 1) the extreme event produces a combinedtotalstorm tidewhichrises above the beach-coast interface elevation toaffectall three subzones,2)the combined total storm tide does not rise above the beach-coast"mrl (6N)41L/4's Vs = 0.025 D r.s 0.'.72oo 0.20.3 0." 0.5 0.6 07"mrl (6H)41L/41s(m2)figure 6.Illustration of mathematical fit for equation (1).1000""'r.(AN) 41L/4ls (m )DFigure7.Illustration of mathematicalfitfor equation (2).DISCUSSIONA favorable result from manyofthe prediction equations tested during the courseofthis investigation isthatmostshowedVs a trend between Vs and the relating 'lit) parameters(e.g.,column 1ofTable 2). Ostensibly, suchconsistencyshouldnotbesurprising since the major factorsknowntocauseseasonal variabilitywereconsidered, and the remainderoftheworkinvolved rearranging the variablestoreduce scatter. Further, the goaltodelineate seasonalitywasa simplified approach (comparedtorelating the entiretimeseriesofmonthlyvalueswhichbecomes increasingly complex).SPECIAL PUBLICATION NO.43equation(2)resultsina mean 60r--..,.---r--,.----r--.---,.-__ grain sizeof0.318mm which. usin9theWentworth Vs'-O classification scheme.isa medium-sized sand (Wentworth, ("'I 20'922).Equations (1) and (2) engender some heterogeneitythatneeds discussion. Both and t/Jl/t/JS are seasonal parameters. Granulometryasitappears in equation (2) is a property element application, although a seasonal response element application is possible and is discussedina later section. The quantity, h mrt however,isnota seasonal measure.Itis, rather,anaverage approximate hourly measure where one tide (diurnal)ortwotides (semi-diurnal) occur in one tidal dayof245/6hours. Hence, h mrt is also a property elementthatis a signature valueforeach site, notingthatitcan vary significantly depending upon the locale. Seasonal mean sea level changeforwhichthere are no site-specific dataforTable 1 localities,isdiscussed in a following section. The resultsofthisworkmightbebest viewedasafirstappraisal until more data

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FLORIDA GEOLOGICAL SURVEY16021986;Savage and Birkemeier,1987),forevents described by scenarios 1, 2 and 3 above. Beach recoveryfollowingtheeffectsofastormwaveevent(i.e.,scenario 4)wasrecorded by JamesP.Morganathis Pensacola Beach, Florida, home (Figure 8);withina day followingstormwaveabatement, the beach had recovered to its pre-stormwidth.123 56189101112Day Figure 8.Exampleofthequickresponse and recoveryofthebeachtostormwaveactivity,Pensacola Beach, Florida, December1974;thestorm peak occurred on December 7 (data courtesyofJamesP.Morgan, personal communications).(m)50(m)0The magnitudeofseasonal shoreline change may varyfromyear-toyear, sinceforanysite some years may have more frequent and intense storm tide andwaveactivitythanotheryears. Horizontal shoreline shifts duetodirect storm and hurricane impacts arenowusually recorded. However,forstormsthatdo not directlyimpactthe shore(i.e.,arefaroutatsea,forexample TropicalStormJuan (Clark,1986)whichaffected Florida) but generate stormwavesthatdo interface elevationbutdoes persist long enoughforthe beachtobeeroded and thecoastis attacked bystormwaves, 3) the combined storm tide doesnotrise above the beach-coast interface elevation and is short enough in duration sothatonly the nearshore and beach are affected, and 4) the extreme event remainsoutatseasothatimpactis indirect(i.e.,a combined totalstormtide doesnotoronlyfractionally reaches the shore) and storm waves primarilyaffectthe nearshore and beach. The combined totalstormtide used hereisdefinedbyDean and others (1989) as thestormsurge duetoastronomical tide,windstress, barometric pressure, and breaker zone dynamic setup,whichdefines the active phenomenaforscenarios 1, 2, and 3(i.e.,the stonn tideevent).Scenario 4 includes only theeffectsofbreakingwaveactivity,including dynamicwavesetup, andistermed the stonnw.ve event.Scenarios 1 and 2 are thosewhich,depending onstormstrength, duration, continental slope, and approach angle, usually produce the design erosion event (Balsillie,1984,1985a,1985b,1986).Probabilistically, the frequencyofoccurrence increasesfromscenario 1to4. Under certain circumstancesofevent longevity, astronomical tides, and nearshore slopes, exceptions can occur. One such exception occurredwhenHurricane GilbertstruckCancun, Mexico in1988.Because there is essentially no continental shelf and nearshore slopes are steep, all eroded sandfromCancun's beacheswasremoved and natural beach recoverywasnot possible. Potentially, other exceptions can occurwhere,forinstance, submarine canyonsmightactasa sediment transport conduit and sand is irremeably lostfromthe littoralsystem.Formostshores, however, continental shelves arewideand nearshore slopes gentle enoughthatbeach recovery to pre-storm dimensionsfollowingsinglestormimpactoccurs in a periodofonetoseveral days (Birkemeier,1979;Bodge and Kriebel,10

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SPECIAL PUBLICATION NO.43cause shoreline erosion, such erosion is usually not measured.Month Figure 9.Monthly average occurrencesofextremeeventwaveeventsfortheOuter BanksofNorth Carolina. P IJI IJo,JJ/IJ a JJII IJ D \'\', Q Beach Sedimentsa EXTREME EVENT TYPE o Extretroplcel(Dolan. Llna,andHayden,1981) "42-1184 oTropica'I(Neumannetal. Hurricane 1981)1940-1980Beach sediments engender some interesting concerns.Howweconsidersedimentsdependsuponwhethergranulometry is appliedasa property elementora response element,whichin turn has aneffecton the dimensional configurationofa numerical representation. As an example, equation (1) requires an additional parameterwithunitsofL1forthe equationtobeunit consistent. Equation (2) was rendered unit consistent by dividingbya granulometric parameterwitha length dimension.Ifthisistobethe applied case,itisusefultonote that when sedimentologic grain size is specified inS.I.units, the mean grain size and standard deviationmomentmeasures have unitsofmm,while51 '5c: o 2 .. c: &io 3... E z & 2... .I Dolan and others (1988) conducted an extensive study onextratropicalstormactivity,assessed alsointermsofstormwavehours,for41yearsofdata(1942to1984)along the Outer BanksofNorth Carolina. These data (Figure 9)showa concerted seasonal trend. In addition, the author extracted from Neumann and others(1981)tropical storms and hurricanes whose tracks camewithinabout250milesofthe Outer Banksforthe period1940to1980.These latter data, also plotted in Figure 9, are addedtothe extratropical data (plottedasa bold, solid line). Hence, the totalstormrecord is nearly represented and, exceptforonly afewdirectimpacts, representstormwaveevents (i.e., scenario' 4 above). For the mid-Atlantic, about35storms occur per year on the average (about26winterevents and 9 summer events),93%ofwhichare extratropical events. In termsofstorm wave duration, Dolan and others (1988), determined using hindcast techniques that on the average,stormwavesoccurforabout 571 hours per year (i.e.,24days per year)forextratropical stormsoffofthe Outer Banks;winterstormwaves persistforan averageof433hours (i.e.,18days), and summer stormwavesabout156hours (i.e.,6.5days). These data strongly correlatewiththe expectationofwidermid-Atlantic east coastsummerbeaches and narrowerwinterbeaches, and illustrate the importantfactthat a largenumber...notafew... winterstonnevents aTe requiredto maintain a nanuwer winterbeachrelativeto a widersummerbeach.11

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FLORIDA GEOLOGICAL SURVEY Table3.Mean annual beach grain size (foreshore slope samples)frommonthlydata,and range in size.Annual Range SiteD(mm)ofD Source (mm) FLORIDAS1.AndrewsSt. Pk.0.290.04Balsillie,1975Grayton Beach0.370.13" "Crystal Beach0.370.15" "J.C. Beasley St.Pk.0.400.11.."Navarre Beach0.410.14.."Fort Pickens Beach0.43 0.27""NORTHCAROLINA Duck0.40 0.19Miller.1984CALIFORNIA Goleta Pt. Beach0.210.16Ingle,1966Trancas Beach0.220.18,"Santa Monica Beach0.260.29.."Huntington Beach0.210.14".LaJolla Beach0.170.04""skewnessandkurtosisaredimensionless. Otherwise, the granulometricmomentmeasures canbespecified all in dimensionless phi units. Beach sands characteristically have a range in sizefrom0.1 mmto1.0mm(U.S.Army,1984)whichoccupies about46%ofthe sand sized rangeofWentworth(1922;i.e.,0.0625to2.0mm). From Table 3,itis apparentthatthe range in mean grain sizes occurring overanannual period is less than1/3ofthe commonly found range in beach sand size(i.e.,0.9mm). Therefore, the typical annual mean grain size,0,forany beachmightbean appropriate measuretoconsiderasaproperty elementprovidedthatsufficient samples are available annuallytoobtain a reliable measure(e.g.,a suiteofmonthlysamples). This impliesthatthere needstobea real difference in mean grain sizesfromsite-to-siteforthe applicationtohave meaning. Even so, theuseofmean grain size alonewithoutconsiderationofstandard deviation, skewness and kurtosis remainssomewhatofa curiosity other than: 1. its use results in a goodfitforequation (2), 2.isproperly applied in equation (2)(i.e.,the largerthevalueofD,the smaller becomes Vs)'3. produces the proper unit dimensionsforthe equation, and 4. has been a considered variable in other research results.Itis generally the case (CASE 1ofTable 4)thatthe coarsest beach sandisfound in theswashzone, andwhichis the only type of sample considered here sinceitdirectly represents energy expendituresofthe littoral hydraulic environment. One might suspectthatswash samples are coarser during the storm than the lull season. However, the range in sediment sizewithinthe sand-sized rangeislimitedforany beachtothe coarsest available materialTable4.Twocasesofsedimentologic responseofmomentmeasurestowaveenergylevels.CASE'CASE 2 EnetgyUveIsAle EnetgylewisAle&.cessive 10 NatfJcc:essive 10Se __1dDkigicSe6nentulagicRespawlSeRespmi5e MEAN GRAIN SIZE Ds-DLIOs>DLSKEWNESS Sk S-SkLISks
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SPECIAL PUBLICATION NO.4313 the negligibleeffectofsand-sized material on runup for larger waves has been noted by Savage (1958). His results strongly implythatrelative to sand size, as the wave height increases thereisreached a point beyondwhichsediment sizewithinthe sand-sized range no longer discriminately responds.Thatis, the levelofwaveenergyisoverpowering eventothe coarsest fractionofsediment availablewithinthe sand-size range. Hence, unless thewaveclimate is closely in equilibriumwithsediment comprising the beach, one wouldnotnecessarilyexpecttofindsignificantly correlative seasonal changes in mean grain size (orforthatmatterskewness, althoughitmightbesomewhatless sensitivetoenergy)withinthe sand-size range. Theauthorlocated datawhereatleast monthly sand samples were collectedwithconcurrentwavedataforsites along theU.S.west,east, and Gulf coasts. Therewasno discernible seasonal correlation betweenwavesand mean sediment grain size. Several typical examples are illustrated in Figure 10. Samsuddin(1989),however, reportstohave found correlationbetweenseasonal changes inwaveconditions, foreshore slope, and sand-sized textural changes along thesouthwestKerala coastofIndia, wherein mean grain size increased and kurtosis decreased during higher seasonalwaveenergyconditions (CASE2,example 1). Samsuddin's one-year investigation,inwhichbeach foreshore sandwasseasonally sampled, may have been afortuitousyear inwhichequilibrium conditions were more nearly manifest. Kerala sand samples are also characterizedbya consistently large standard deviationwhichallowsforgreaterleewayin sorting potential (0.6to0.7phi comparedto0.2to0.55phi commonlyfoundforU.S.beach sands). Unfortunately, Samsuddin did not describe the mineralogyorshape characteristicsofthe samplesT e-I o.so CUI1,---...... __....TI..e-) 3zSt. .... ""... D Uh>-"' ........__ '""-e_1 It.Z '.1 ..&.....I.""""J...J.."SO.DJF SO.D_Ill figure 10.Typical examplesoftime series relationofmonthly data for breaker height.waveperiod, and foreshore slope grain size for California (data from Ingle, 1966) and northwestern Rorida panhandle (data from Salsillie. 1975) sites.whichmayormaynotdifferfromthecharacteristicallyrounded. quartzose feldspathicU.S.beach sands consideredinthiswork.There also occursthecase (CASE 2, example 2) where a beach is comprisedofsediments exceeding the sand-sized range.Anexample is Oceanside Beach, Oregon, mentioned earlier, inwhichallthesand-sizedsummerbeach material is removedtoexpose awintercobble beach. Under such conditions, one wouldexpectthatsediment coarsening,asreflectedbythe mean grain size and skewness, would resultfromhigherwaveenergy levels becauseofthe excessive sizeofcoarser sediments. When singularly considered, the 1stmomentmeasure (mean grain size) tellsusnothing about the natureofthe distribution.

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FLORIDA GEOLOGICAL SURVEYFromthepreceding discussion,itis apparentthattwogeneral cases canbeidentifiedwherewaveenergy levelseitherexceedstabilityconstraintsofthe coarsest fractionofthe sedimentologic distribution, ortheydo not. For three moment measures consideredtobest represent sedimentologic responsetothewaveenergy force element,stormand lull season responses are listed in Table 4. Forthetwocases (Table 4)onlythe kurtosis persists in providing a response, because the4thmoment measure isnotrenderedineffectivetoregister a changebyexcessivewaveenergy levels. Therefore, a parameterforconsiderationthatmore nearly quantifies sedimentologic responsemightbe given by: The2ndmomentmeasure (standard deviation) tells us about the dispersion about the 1stmomentmeasure, but leaves no insightastohowthe distribution departs either symmetrically or asymmetricalfromthe normalbell-shaped frequency curve (orfromthe straight lineforthe cumulative curve plotted on standard probablity paper). Such departure is a characteristicofthe tailsofthe distribution aboutwhichknowledge is progressively imparted tousby considering the 3rd moment measure (skewness),4thmoment measure, (kurtosis), and highermomentmeasures (Tanner, personal communication; Balsillie, 1995).Itis, infact,the tailsofthe distributionwhichcan provide a great dealofenvironmental information.Ithas been demonstrated,forinstance,thatthere is an inverse relationship between the kurtosis and the levelofsurfwaveenergy expenditure (Silberman,1979;Rizk,1985;Rizk and Demirpolat,1986;Tanner,1991,1992).Tanner(1992)has reported a correlation betweensealevel rise and kurtosis, because the rise component is attendedbyan increase in surf wave energy expenditure. e =(20+Sk)KD(3)14where the moment measures are defined in Table 4. The 3rd moment measure (skewness) of equation (3) has a valueof20added to itinordertoassurethatpositive values will result. The parameter()when evaluated usingS.I.units has unitsof V' (dimensionlessunitsresultwhengranulometric measures are evaluatedinphi units). By using seasonal valuesof 8, thatis, 8 s forthe storm season and 8L forthe lull season,itmaybepossibletocompile a sedimentologicresponse elementparameterthatcanbeincorporated into equation (1). The proper formofthe parameter, including equation (3), however, requires additional data, research, and testing. AstrDllomicalTitles Thatmeanastronomicaltideelevations exhibitcyclicseasonal variability has long been established (Marmer,1951;Swanson,1974;Harris,1981)and is includedintide predictions. TheU.S.DepartmentofCommerce(1987a,1987b)states, however,thatat....ocean stations the seasonal variation is usually less than half afoot.Marmer(1951)notesthatseasonal variation in termsofmonthly mean sea levelforthe U.S.canbeasmuchas0.305m(1foot; Table 5); some examplesfortheU.S.east, Gulf, andwestcoasts are illustrated in Figure11.Based on the many yearsofmonthly data, researchers (Marmer,1951;Harris,1981)note slight variations in the seasonal cyclefromyear-to-year, but also recognize the periodicity in peaks and troughs over the years. For muchofourcoast, lower mean sea levels occur during thewintermonths and higher mean sea levels during the fall. Harris (1981 ) inspected the recordtodetermineifstormand hurricane occurrencewasin anywayresponsibleforthe seasonal change,butfound....nosystematic variability. Galvin (1988) reportsthatseasonal mean sea level changes are not completely understood,butsuggests that there appearstobetwoprimary causesforlowerwintermean tide

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SPECIAL PUBLICATION NO.43levelsfortheU.S.east coast:1.strongnorthwestwinterwindsblowthewaterawayfromshore, and 2.watercontractsasitcools.Henotesthatwindsare moreimportantin shallowwaterwhere tide gauges are located,butthatcontraction becomes important in deeper waters.Swanson(1974)also notes....seasonal changes resultingfromchanges in direct barometric pressure, steric levels, river discharge, andwindaffectthemonthlyvariability. Seasonal variation in tidesisusuallyattributedtotwoharmonicconstitutents:onewitha periodofoneyeartermed thesolarannual tidalconstituent,and theotherwitha periodofsixmonthstermed the solar semiannualconstituent(Cole,1997).Someconsiderthesetobemeteoroligical in nature,ratherthan astronomic.However,becausetherootcauseofcyclicseasonalweatheristhechanging declinationofthe sun,theyshould more nearly be astronomical in origin. Harmonic analysisofthe annual tidal recordcaneasily determine the amplitude and phaseofeachofthese constituents, thereby providing a mathematical definitionofthe seasonal variation. (George M. Cole, personal communications.) Comparing the closest appropriatecurvefromFigure 11toFigures 2 through 5, itis apparentthatthelowestseasonal standofmean sea level and, therefore, average astronomical tideeffectsoccurswhenthe beach is narrowestforStinson Beach andTorreyPines Beach, California, andJupiterBeach, Florida. For Gleneden Beach, Oregon,narrowbeachwidthsandmonthlyaverage tidal highs seemtobemore nearly in phase. Therefore,itisnotclearthatseasonal changes in astronomical tidessignificantlyaffectseasonal shoreline variability,atleastnotin termsofaveragemonthlymeasures. Quite clearly, however,suchdata needs tobeprocuredforeach sitetoconfirma correlationorlack thereof. Should the proper correlation consistentlyTable5. Seasonalrange inmonthly average waterlevels.I SiIe I v:" IhII-I(m) Law U. S. fastCoast New York. 190.177Feb SepAtlanticCity190.165Feb Sep Baltimore190.238Feb Sep Norfolk190.177Feb Sep Charleston190.253MarOctMayport190.314MarOct Miami Beach 17 0.259MarOctU.S. a.Coast KeyWest190.216MarOctCedar Key100.244Feb Sep Pensacola190.232Feb Sep Galveston190.247JanSep Port Isabel40.262FebOctU.S. WestCoast Seattle190.159AugDec Astoria190.219AugDec CresentCity140.180AprDec San Francisco190.104AprSep Los Angeles190.152AprSepLaJolla190.143AprSep San Diego190.152AprSep Notes:1.h=seasonal range based on averageofn yearsofmonthly means wheremonthlymeans are averageofhourly heights;2.San Diego gaugeislocated in San Diego Bay; 3. Astoria gauge is located15miles upstream from the mouthofthe Columbia River.occur(e.g.,lowmonthly average mean sea level -widerbeaches, and highmonthlyaverage meansealevel -narrowerbeaches) then a relating parameter needstobeincorporated in the quantifying predictive relationship(s).Itisofconsequencetonote,forthedataofTables 1 and 4,thatthe seasonal rangeofmonthly average mean sea level isfrom9 to33%ofthe mean rangeoftide(hmrt).APPUCAnONOFRESULTSWhile horizontal shorelineshift(or beachwidthchange) addressesonlyone15

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FLORIDAGEOLOGICALSURVEY III u. S. GULF coasTMONTH u. s. weST COAST ,M A M A 0 DRgure11.Monthlyvariation in sea levelforthecontiguous United States (after Manner,1951).dimensionofa measureofbeach change,itdoes servetostraightforwardly punctuate the natureofthe phenomenon. The mannerofapproaching quantificationofthe phenomenon here, allowsfora simply applied methodologythatisusefulforeducational,technical,and planning purposes.General KnowledgeSeasonal beach shifts arenotgenerallyknownby the layman. In Florida,with35,000newresidents arrivingmonthly(Shoemyen and others,1988),newcoastal property owners have been alarmedafterpurchasing ocean-fronting property during the "summer"whentheir beach iswide,tofindorreturntofind a narrowwinter"beach, believingthattheyhaveunwittinglypurchased eroding property. OstensiblY, this might result in an applicationfora permittoconstructa coastal hardening structure suchasa bulkhead or seawallwithoutinvestigating seasonal beachwidthvariation on the partofthe applicant, the applicant's design professional,orthe permitting16agency. The resultsofthis paper provide a quantitative basis uponwhichtoinform the public, and a method to assess a permit application. SeawanlllDundary of PublicversusPrivate OwnershipThe boundary between private (i.e., upland) and public (i.e., seaward) beach ownership is fixed by some commonly applied tidal datum. For mostoftheU.S.this is the planeofmean highwater(MHW) which, whenitintersects the beach or coast forms, the mean highwaterline. However,unlikeotherriparianownershipdeterminations (i.e., fluvial, lacustrine and estuarine), littoral properties must, in addition, contendwithsignificantwaveactivitythat seasonally varies. Hence,ocean-frontingbeachesall-too-oftenexperience cyclic seasonalwidthchangesofa magnitude long recognizedasproblematic in affixinganequitable boundary (Nunez,1966;Johnson,1971;Hull,1978;O'Brien,

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SPECIAL PUBLICATION NO.431982;Graber and Thompson. 1985; Collins and McGrath. 19891. Many investigators have suggestedthatthe legal boundaryforoceanfronting beaches should notbecontinuously movingwiththe seasonal changes. but shouldbethe most landwardor"winter"lineofmean highwaterINunez.1966).Selectionofthe"winter"MHWlinewouldbethe most practical to locate andwouldbethe most protectiveofpublic interest by maintaining maximum public accesstothe shoreline (Collins and McGrath,1989).InFlorida, the ocean-fronting legal boundary seasonal fluctuation issuewasdeliberated upon in StateofFlorida, DepartmentofNatural ResourcesvsOcean Hotels, Inc. (StateofFlorida, 1974)asitrelatedtolocating theMHWline fromwhicha50-footsetbackwastobedetermined. Judge J.R.Knott, upon considerationofall the options. renderedthefollowing decision: ThiseDUltu,.,.fotweoncludesth the winter and most1MHIwan/ mean highw.r.r line mustbeselectedasthe boundary Iwtween the stat.and the upland owner.In so doingthe eourthashad to balaneethepublicpoDey favoring private littoral ownership against thepublie poOey of holdingthetideland in trust forthe people,whetwthepreseNation of a vital pubHerightisseeured withbutminimal .ffectupontheinte,.sts ofthe upland owner.A1966California CourtofAppeal decision rejected the applicationofa continuously moving boundaryinPeoplevsKent Estate (StateofCalifornia,1966).However. no decision has been renderedastowhatlinetouse (Collins and McGrath,1989).More recently, however. Collins and McGrath (1989) report:The AttomeyGeneral'sOffiee in Califomia luis offetwdits informal opinion thilt, if squarelyfaeed withthe issue, Califomia eourts would followthe twasoning intheRorida ease and adoptthe "winter andmost landward lineofmeanhigh tide" as the legal17 boundarybetweenpublie tidelands and private uplands ... (it shouldbe undemoodthat such aboundary, while relatively stable, wouldnotbe permanently fixedbutwouldb.ambulatorytotheextent th.reoccurs long term aecretion or erosion). Collins and McGrath also discuss special issues suchasshore and coastal hardening structures,artificiallyinduced accretionofsand.etc.,and theirworkis highly recommendedforfurtherreading. However, no formal legal adoptionofthelittoral MHW boundary has found nationwideacceptance. This is symptomaticofmankind's tendencytogive credencetocodesofanthropicconductthrough the t.ws.fMan (published in local codes, statestatutes,and federal regulations, etc.) buttoessentially ignore the environment andhowitworksthrough the LrNs .f NIItuIe (published in scientific papers and journals). Untilabalance is more nearly achieved,weshallcontinuetoexacerbatetheenvironmental crisisthathas befallenusall. The resultsofthis paper provideforone small aspectofthe behaviorofnatureanopportunitytoachieve a balance betweenthetwosetsoflaws.Long-Term Shoreline ChangesThe initial motivationtoinvestigate this subject was the developmentofa methodologytoanalyze and assess longtermshorelinechanges.Quantitative behavioroflongterm shoreline changetoassess coastal stability is best accomplished using actual historical surveys. In Florida,asmanysurveysaspossible are locatedforthe period from about1850topresent (aerial photographyisusedwherean historical hiatus occurs), usually resulting in from 8 to14points to represent the historical shoreline position (Balsillie.1985a,1985b;Balsillie and Moore. 1985; Balsillie and others,1986).These data are assessed alongshoreata spacing of approximately300m. Hence. historical change rate analysis

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FLORIDAGEOLOGICAL SURVEYVF Rgure 12.Example of long-term shorelinechangerate (solid lines) temporal analysis using seasonal shoreline shift data(dashed lines);seetextfor explanation.Ofthe numerical methods availabletoanalyze such data, many can actually magnify the uncertainty and/or error associatedwiththe final resultsofaninvolved computational approach. Cautionwithrespecttothis aspectofanalysis cannotbeover emphasized. Infact,the topic is so importantthata seriesofstandard equationsforassessing the propagationoferror in computing have been provided in the Appendix.20001950a:-6.25m/YF c:-0.45m/YFb:+110m/YFd:+1.64m/yrmagnitudethatwemust keep the numberofcomputational stepstoa minimum in ordertominimize the propagationoferrorincomputing (bearinmind thatinadditiontothe tempol'lll analytical component a spatial component remains,whichfurther increases analytical computation). The bottomline"isthatweneedtousethemostappropriateandcomputationallysimpleanalyticalmethodologyavailable. Themostappropriate statistical analytical tool is undoubtedly tIendanalysis whichalready includes measuresofdetermining the associatederrororvariability.Inaddition,whatwemight learn andquantifyabout nature'sownsystematic variability canbeusedtoour advantage both in termsofassessing the acceptabilityofdata, and asananalytical tool. Such is the usefulnessofhorizontal seasonal shoreline change. An exampleoftemporal analysis is illustrated in Figure 12fora locality about2.7kilometers southofa major inlet on the east coastofFlorida. Equation (1)wasevaluated using the appropriate wave dataof1900Art""lalNou.Is_80".1JettyConstructionaeg_n ,"... I ... InletArtlflcl_lIyCut1I ....," a.b' ... .,... ..---_-.I,... ..,"C......'..._-'!. I --...... d. .. -,--'----,# 200100400300v(m)analyticalanalytical tempol'lll aspatialrequires both acomponentand component. The natureofhistorical shoreline location data is suchthatthere is associated error and variability. Surveying error includes inherent closure errors, error duetoolder technologies, and non-adjustment errorformore recent vertical and horizontal epoch readjustments. Survey nets establishedforcountysurveys may not precisely relatetoadjacentcountynetsastheywouldin a state-wide net. Long-term sea level changes, though slight,affectlong-term shoreline changes. These sourcesoferrormaybecalled map-source errorsafterDemirpolat and others(1989),forwhicha magnitudeof9to15mmaybeappropriate (Demirpolat and others, 1989). Interpretive plottingoferrorsofshoreline location (depending on data concentration) on original survey mapsmustbeassumed,especiallyforolder maps. Present digitizing technology results in an errorof3to4m (Demirpolat and others,1989).Exceptforrecenttechnologies,magnitudesoferrorsforexamples suggested above arenotknownwithcertaintyin the majorityofcases. Even so,itcanbeenvisioned thattheyareofsufficiently large 18

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---SPECIAL PUBLICATION NO.43Thompson('977)and tidal data from Balsillie('987a). To the result.onestandard deviation was added to yield a predicted seasonal variability measure of50.5m.Startingwiththe most recent data and moving back in time, regression techniques are usedtodetermine a trend line (solid lineinFigure 12) aboutwhichplus and minus one-half the seasonal variability measureisaffixedinthe vertical direction (dashed lines in Figure 12). The slopeofthe trend lineofthe time seriesisthe rate of erosionoraccretion(azero slopeorhorizontal line represents stability).Nowthe seasonal variability measure becomes a valuable asset towards identifying spurious data or long term change segments in shoreline behavior. For instance,ifa point lies outsidetheseasonal variability envelop in the middleofsegment d, onewouldconclude that either seasonal variabilitywasextremeforthatyear (forwhichthere are undoubtedly no records)orthe survey was made immediately following extreme event impact (either storm tideorwaveeventforwhichthere are probably no records).Ineither case,wehave reasontonot include the data pointinour analysis, since there are sufficient data pointsforthe segmenttosuggest a strong trend. Interactively, trends in segment datlocalities upanddowncoast canbeusedtoverifysuch a trend in the spatial componentofthe change rate analysis. We also can use historical information about the areatoassist in analysis. For instance,weknowthatthe inletwasartificially constructed in1951,andjettyconstruction began in1953.Furthermore, artificial nourishment southofthe inlet began in1974.Eachofthese eventsiscoincidentwitha new episode in shoreline behavior, and maybeverifiedwithsimilar analysesatnearby upand down-coast sites. Notethatthere are toofewdata points to quantify the shoreline change trendforsegment c; either additional data points are required or verification/readjustmentfromanalysesat19nearby adjacent sites are required to assure quantificationofrepresentative shoreline change. Project Design and Pedonnance Assessment Both Iong-tenn changes and eJtt1'eme event impacts have long been considered in assessing coastal development design. activities (until recently the formerhasby and-largebeenqualitative).Inproper order,long-termchangesshouldfirstbe determined, followedbythe design extreme event impact. Thefirstdetermination allowsforprudent sitingofthe developmentactivity,and the secondforresponsible structural design solutionstowithstandstormtide, wave, and erosion event impacts. However,withoutknowledgeof BellSOIIII1shoteIineshifts fora particular locality, uncertainty willbeintroduced into suchassessment.Followinglong-termdeterminationofwherethe shorewillbe(e.g.,say, a standard 30-year mortgage period)itwould,forinstance,beprudenttoadjust the beachwidthofa given topographic surveytoits narrowest expected seasonal dimension, thentoapply extreme event analyses. Considering the significant outlayofresourcesforbeach nourishment projects,itwould seem appropriate to consider seasonal shoreline variability both in project design and in assessing performance. The controversial issueofwhether coastal hardening structures(e.g.,seawalls, bulkheads, revetments) promote the erosionofbeaches fronting them,isone of complex proportions. Without being long-winded, the issue might finallyberesolvedbyinspecting long-term shoreline location data. Again, however, seasonal shoreline shifts would require quantification and applicationinthe analysis.Atthe very least, methodology developed here would allow one to determineifseasonal shoreline change wasofsignificant proportions thatitshouldbeconsidered in design applications. Using

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FLORIDAGEOLOGICALSURVEYknownwave. tidal. and sedimentological dataitwouldbea straightforward task to compile such results. particularlyinFlorida where the coasthasbeen monumented.CONCLUDINGREMARKSFor muchofour shoreline, seasonalshiftsin shoreline position occur. While the phenomenonhasbeen the subjectofconsiderableconcern,nospecificquantification has. untilnow,surfaced.Ithas been noted earlier that some shorelines(e.g.,east-west trending shores) apparently donotexhibit seasonal shifts. This maybeduetostormwaveimpacts occurring in groupsforperiodsofless thanmonthlyand/or duetoclimatic changeaffectingstormfrontazimuths relativetoshoreline azimuths. Correlation mightbeattainedbyselectingmostand least activemonthlyaverages, orbyapplying moment statistics.AnhistoricalstudyofGulfofMexicostormwaveand direct coastal impacts,asDolan and others(1988)conductedfortheAtlanticOceanoffNorth Carolina, is needed. Resultsofsuch astudywouldshed light on the regional behaviorofeast-west trending shoresofthe central Gulf, and would alsobeapplicabletothe more nearly north-south trending shoresofthelowerGulf coastsofFlorida and Texas. While the methodologyforassessing average seasonal shoreline and beachwidthvariability canbeusedfora varietyofimportantapplications, the developments presented here are afirstappraisal. Theintentofthisworkis to invoke interest in the subject andtoactasa pleaforadditional data onwhichtotestexisting predictive methodology and/or develop more exacting technology. For instance, while thisworktreats straight ocean-:fronting beaches composedofsand, seasonal changesofpocketbeaches mightbetreated by20including seasonal wave approach angle changes, and data for beaches composedofsand and pebbles (i.e.a very large standard deviation) would help in understanding the roleofthe sedimentologic property element. ACKNOWI.DGEMENTS Reviewofanearlier manuscript leadingtothis paper provided significant guidance, and those comments and suggestions fromPaulT. O'Hargan, Joe W. Johnson, George M. Cole, Alan W. Niedoroda, and Gerald M. Ward are gratefully acknowledged. JamesR.Allen and RalphR.Clark, and WilliamF.Tanner reviewed the presentformofthepaper and made several valuable suggestions. Special thanks are also extended to Kenneth Campbell,EdLane,Jacqueline M. Lloyd, Frank Rupert, and ThomasM.Scottofthe Florida Geological Surveyforthe many useful editorial comments.REFERENCESAguilar-Tunan,N.A.,and Komar,P.D.,1978,The annual cycleofprofile changesoftwoOregon beaches: TheOreBin, v. 40,p.25-39.Aubrey,D.G., 1979, Seasonal patternsofonshore-offshoresedimentmovement: JournalofGeophysical Research, v. 84,p.6347-6354.__ Inman,D.L., and Nordstrom,C.E.,1976, Beach profilesatTorrey Pines, California:inProceedings,15thInternationalCoastalEngineering Conference, v. 2,p.1297-1311.

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'-.SPECIAL PUBLICATION NO.43Sa/sillie,J.H.,1975,Analysis and interpretation of Littoral Environment Observation(LEO)andprofile data along the western panhandle coastofFlorida: Coastal EngineeringResearchCenterTechnicalMemorandum No. 49,104p.1984,A multiple breakingwavetransformationcomputer model: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 84-4,81p._____ 1985a,Calibration aspectsforbeach and coast erosion duetostormandhurricaneimpactincorporatingeventlongevity:Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum N ..85-1,32p._____,1985b,Verificationofthe MSBWT numerical model: coastal erosionfromfourclimatological events and littoral wave activityfromthree storm-damaged piers: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 85-2,33p.1986,Beach and coast erosion duetoextreme event impact: Shore and Beach, v. 5,p.22-37.,1987a,Predicted open coast-----tidal datumsforthe Florida east coast: Florida Department of Natural Resources, Division of Beaches and Shores Technical and Design Memorandum 87-1, 68p.21 1987b,Seasonal variation in-----shoreline position and application to determinationoflong-term shoreline change trends: (Unpublished draft report), Florida DepartmentofNatural Resources, DivisionofBeaches and Shores, 59p._____, and Moore,S.D.,1985,A primeronthe applicationofbeach and coast erosiontoFlorida coastal engineering and regulation: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 85-3.____ O'Neal, T.T.,and Kelly, W.J.,1986,Long-term shoreline change ratesforBay County, Florida: Florida DepartmentofNatural Resources, Beaches and Shores Special Report No.86-1,84p.Barry,B.A.,1978,Errors in practical measurement in science, engineering and technology:NewYork, John Wiley&Sons,183p.Bascom, W.H.,1951,The relationship between sand size and beach-face slope: Transactionsofthe American Geophysical Union, v. 32,p.866874. 1980,Waves and beaches:-----'GardenCity,AnchorPress/Doubleday,366p.Berrigan,P.D.,1985,Seasonal beach changesatthe Taraval seawall: Shore and Beach, v. 53,p.9-15. and Johnson,J.W.,1985,-----Variationsofwaveattack along Ocean Beach,SanFrancisco, California: Shore and Beach,v.53,p.7-15.

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FLORIDA GEOLOGICAL SURVEYBirkemeier, W.A.,1979,The effectsofthe 19 December1977coastal stormonbeachesinNorth Carolina and New Jersey: Shore and Beach, v. 47, no.1,p.7-15.Bodge,K.R'tand Kriebel,D.L.,1986,Storm surge andwavedamage along Florida's gulf coast from Hurricane Elena: UniversityofFlorida, Coastal and Oceanographic Engineering Department. Bokuniewicz,H.J.,1981,The seasonal beachatEast Hampton,NewYork: Shore and Beach, v.49,p.28-33._____,'and Schubel,J.R.,1987,The vicissitudesofLong Island beaches,NewYork: Shore and Beach, v. 55,p.71-75.Brampton,A.H., and Beven,S.M.,1989,Beach changes along the coastofLincolnshireU.K.(1959-1985):Coastal Sediments'89,v. 1,p.539554.Clark,R.R.,1986,TheimpactofHurricane Elena and Tropical Storm Juan on coastal constructioninFlorida: Florida DepartmentofNatural Resources, Beaches and Shores Post-Storm Report No. 85-3,142p.Clarke,D.J.,and Eliot,I.G.,1983,Mean sea-level and beach-width variationatScarborough, Western Australia: Marine Geology, v.51,p.251-267.Cole,G.M.,1997,Waterboundaries,NewYork, Wiley and Sons, Inc.,193p.Collins,R.G., and McGrath,J.,1989,Whoownsthe beach? Finding a nexus gets complicated: Coastal Zone'89,v.4,p.3166-3185.22Darling, J. M.,1964,Seasonal changesinbeaches of the North Atlantic coastofthe United States: Proceedingsofthe 9th Conference on Coastal Engineering,p.236-248.Davis,R.A,Jr.,1976,Coastal changes, eastern Lake Michigan,1970-73:Coastal Engineering Research Center Technical Paper No.76-16,64p.Dean,R.G.,1973,Heuristic modelsofsandtransportinthesurfzone: Conference on Engineering Dynamics in the Surf Zone, Sydney, Australia,7p.____, Chiu, T.Y.,and Wang,S.Y.,1989,CombinedtotalstormtidefrequencyanalysisforCollier County, Florida: Florida DepartmentofNatural Resources, Beaches and Shores Storm Tide Report No. 89-1. Demirpolat, S., Tanner, W.F.,Orhan, H., Hodge,S.A.,and Knoblauch, M.A,1989,High-precisionstudyofFloridashorelinechanges:CoastalSediment'89,p.683-697.DeWallAE.,1977,Littoral environment observations and beach changes along the southeast Florida coast: Coastal Engineering Research Center Technical Paper No.77-10,171p.__ __ and Richter, J.J.,1977,Beach and nearshore processes in southeastern Florida: Coastal Sediments'77,p.425-443.Dolan,R.,1965,Seasonal variations in beach profiles along the Outer BanksofNorth Carolina: Shore and Beach, v. 33,p.22-26.___ .__-' Lins, H., and Hayden, B.,1988,Mid-Atlantic coastal storms: JournalofCoastal Research, v. 4,p.417-433.

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--....;sSPECIAL PUBLICATION NO.43_____, Vincent, L., and Hayden, 8., 1974. Crescentic coastal landforms: Zeitschrift fur GeomorphologieN.E.,v. 18,p.1-12. Eliot,I.G.,and Clarke,D.J.,1982,Seasonal andbiennialfluctuation in subaerial beach sediment volume on Warilla Beach, New South Wales: Marine Geology, v. 48,p.93-103.Everts,C.H.,DeWall,A.E.,and Czerniak, M. T.,1980,Beach and inlet changes at Ludlam Beach,NewJersey: Coastal Engineering ResearchCenterMiscellaneousPaper No. 80, 146p. Felder,W.N., and Fisher, J. S.,'980,Simulation model analysisofseasonal beach cycles: Coastal Engineering, v. 3,p.269-282.Galvin,C.J.,Jr.,1988,The annual tide in Chesapeake Bay: Coastal Engineer Notes,p.3-4. Garrow,H.C.,1984,Quantificationofshoreline rhythmicity:inProceed ings,17thInternational Coastal Engineering Conference, v. 2,p.2165-2180.Gorsline,D.S.,1966,DynamiccharacteristicsofwestFloridagulfcoast beaches: Marine Geology, v. 4, p.187-206.Graber,P.H.F.,and Thompson, W. C.,1985,The issues and problemsofdefining property boundariesontidalwatersin California: California's Battered Coast, Proceedingsofa ConferenceonCoastal Erosion, SanDiego,CaliforniaCoastalCommission,p.16-25.Hale, J.5.,1975,Modeling the ocean shoreline: Shore and Beach, v. 43,p.35-41.23Hattori,M.,and Kawamata,R.,1980,Onshore-offshore transport and beach profile change:inProceed ings,17thInternational Coastal Engineering Conference, v. 2,p.1175-1193.Harris,D.L.,1981,Tides and tidal datums in the United States: Coastal Engineering Research Center Special ReportNo.7,382p.Hobson,R.D.,1977,Reviewofdesign elementsforbeach-fill evaluation: Coastal Engineering Research Center Technical Paper No. 77, 51p.Hull,W.V.,1978,The significanceoftidaldatumstocoastalzonemanagement: Coastal Zone'78,p.965.Ingle, J. C., Jr., 1966; The movementofbeach sand, Elsevier, Amsterdam, 221p.Inman,D.L.,and Filloux,V.,1960,Beach cycles relatedtotide and localwindwaveregime: JournalofGeology, v.68,p.225-231.Ippen,A.T., and Eagleson,P.S.,1955,Astudyofsediment sorting by wave shoaling on a plane beach:ProceedingsoftheCoastalEngineering Specialty Conference,p.511-536.James, W.R.,1974,Borrow material texture and beach fill stability:inProceedings,14thInternational Coastal Engineering Conference,p.1334-1349.,1975,Techniques in eval------'uating suitabilityofborrow materialforbeach nourishment: CoastalEngineeringResearchCenterTechnical MemorandumTM-60.

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FLORIDA GEOLOGICAL SURVEYJohnson,J.W.,1949,Scaleeffectsinhydraulic models involvingwavemotion: Transactionsofthe American Geophysical Union, v.30,p.517-525._____ 1971,The significanceofseasonal beach changesintidal boundaries: Shore and Beach, v.39,no. 1,p.26-31.Kadib, A.L,and Ryan, J.A.,1989,San Diego region seasonal and longtermshoreline changes: Coastal Zone'89,v.2,p.1755-1765.Katoh, K., and Yanagishima,5.,1988,Predictive modelfordaily changesofshoreline:inProceedings,21stInternational Coastal Engineering Conference, v. 2, p1253-1264.Kinose, K., Okushima,5.,and Tsuru, M.,1988,Calculationofon-offshoresandmovementandwavedeformation on two-dimensional wave-current coexistent system:inProceedings,21stInternational Coastal Engineering Conference, v.2,p.1212-1226.Krumbein, W. C., and James, W.R.,1965,A lognormal size distribution modelforestimating stabilityofbeach fill material: Coastal EngineeringResearchCenterTechnicalMemorandumTM-16.Larson, M., and Kraus,N.C.,1988,Beach profile change: morphology,transportrate, and numerical simulation:inProceedings,21stInternational Coastal Engineering Conference, v. 2,p.1295-1309.Marmer,H.A.,1951,Tidal datum planes:U.S.DepartmentofCommerce, Coast and Geodetic Survey, Special Publication No.135,142p.24Miller,H.C.,1984,Annual data summaryfor1980,CERCfield researchfacility:Coastal Engineering Research Center Technical ReportCERC81-1._____, Leffler, M. W., Grogg, W.E.,Jr., Wheeler,S.C., and Townsend,C.R.,III,1986a,Annual data summaryfor1982CERCfieldresearchfacility:CoastalEngineeringResearchCenterTechnical ReportCERC86-5.__ Grogg,W.E.,Jr., Leffler, M. W., Townsend,C.R.,III,and Wheeler,S.C.,1986b,Annual data summaryfor1983CERCfieldresearchfacility:CoastalEngineeringResearchCenterTechnical ReportCERC86-9._____, Grogg, W.E.,Jr., Leffler, M.W.,Townsend,C.R.,III,and Wheeler,S.C.,1986c,Annual data summaryfor1984CERCfieldresearchfacility:CoastalEngineeringResearchCenterTechnical ReportCERC86-11.Miller, M. C.,1983,Beach changesatHolden Beach, North Carolina,197074:Coastal Engineering Research Center Miscellaneous Report No.835,194p.Morisawa, M., and King,C.A.M.,1974,Monitoring the coastal environment: Geology, v. 2,p.385-388.Neumann,C.J.,Cry,G.W.,Capo,E.L,and Jarvinen,B.R.,1981,Tropical stormsofthe North Atlantic Ocean,1871-1980:U.S.DepartmentofCommerce, National Oceanic and Atmospheric Administration,174p.

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SPECIALPUBLICATIONNO.43Nordstrom,C.E.,and Inman,D.L.,1975,Sand level changes on TorreyPinesBeach,California:CoastalEngineeringResearchCenterMiscellaneous Paper No. 11-75,166p.Nunez,P.,1966,Fluctuating shorelines and tidal boundaries: an unresolved problem:SanDiegoLawReview,v. 6, p.447,466-469.O'Brien,H.P.,1982,Our wandering high tide lines: Shore and Beach, v. 50,p.2-3.Otvos,E.G.,1965,Sedimentation-erosion cycleofsingle tidal periods on Long Island Sound beaches: JournalofSedimentary Petrology, v. 35,p.604-609.Passega,R.,1957,Texture as characteristicofclastic deposition: Bulletinofthe American AssociationofPetroleum Geologists, v.41,p.1952-1984.1964,Grain size repre sentation by CM patternsasa geologicaltool:JournalofSedimentary Geology, v. 34,p.830847.Patterson,D.R.,1988,Beach nourishmentatSurfsideSunset Beach: the Orange County beach erosion project, Orange County, California:inProceedings, Beach Preservation Technology'88,p.47-58.Pawka,S.5.,Inman,D.L.,Lowe,R.L.,and Holmes,L.,1976,Wave climateatTorrey Pines Beach: CoastalEngineeringResearchCenterTechnical Paper No.76-5,372p.25Pritchett,P.C.,1976,Diurnal variationsinvisually observed breaking waves: Coastal Engineering Research Center Miscellaneous Report No.76-8.Quick, M. C., and Har,B.C.,1985,Criteriaforonshore-offshore sediment movementonbeaches:inProceed ings, Canadian Coastal Conference,p.257-269.Ricker,W.E.,1973,Linear regression In fishery research: Journalofthe Fisheries Research BoardofCanada, v.30,p.309.Rizk,F.F.,1985,Sedimentological studiesatAlligator Spit, Franklin County, Florida:M.S.Thesis, Geology Department, Florida State University, Tallahassee,FL,171p._____, and Demirpolat,5.,1986,Prehurricane.vs.posthurricane beach sand, Franklin County, Florida: ProceedingsoftheSeventhSymposiumonCoastalSedimentology Suite Statistics and Sediment History, (W.F.Tanner, ed.), DepartmentofGeology, Florida State University, Tallahassee,FL,p.129-142.Samsuddin,M.,1989, Influenceofseasonal changesinthe textureofbeach sands, southwestcoastofIndia: JournalofCoastal Research, v. 5,p.57-64.__ ----:,...--_" and Suchindan,G.K"1987,Beach erosion and accretion in relation to seasonal longshore current variation in the northern Kerala Coast, India: JournalofCoastal Research, v.3,p.55-62.

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FLORIDA GEOLOGICAL SURVEYSavage,R.J., and Birkemeier, W. A.,1987,Storm erosion data from the United States Atlantic coast: Coastal Sediments'87,p.1445-1459.Savage,R.P.,1958,Wave run-up on roughened and permeable slopes: Transactionsofthe American SocietyofCivil Engineers, v.124,Paper No.3003,p.852-870.Saville,T.,Jr.,1957,Scaleeffectsintwodimensionalbeachstudies:Transactionsofthe International AssociationofHydraulic Research,p.A3-1-A3-10.Sawaragi, T., and Deguchi,I.,1980,On offshore sediment transport rate in thesurfzone:inProceedings,17thInternational Conference on Coastal Engineering, v. 2,p.1194-1214.Schneider, C., and Weggel, J. R.,1982,Littoral Environment Observation(LEO)data summaries, northern California,1968-1978:CoastalEngineeringResearchCenterMiscellaneous Report No.82-6,164p.Schwartz, M.L.,1967,Littoral zone tidal cycle sedimentation: JournalofSedimentary Petrology, v.37,p.677-709.Seymour,R.J.,and Castel,D.,1988,Validationofcross-shore transport formulations:inProceedings,21stCoastal Engineering Conference, v. 2.p.1676-1688.Shepard,F.P.,1950,Beach cycles in southern California: Beach Erosion Board Technical Memorandum No.20,26p.26_____, and LaFond,E.C.,1940,Sand movements along the Scripps Institution pier: American JournalofScience, v.238,p.272-285.Shoemyen,A.H., Floyd,S.S., and Drexel,L.L.,1988,1988Florida Statistical Abstract, University PressesofFlorida, Gainesville,FL.Silberman,L.Z.,1979,A sedimentologicalstudyofthe Gulf beachesofSanibel and Captiva Islands, Florida: M.S.Thesis, Geology Department, Florida State University, Tallahassee,FI,132p.SonuC.J.,and Russell,R.J.,1966,Topographic changes in the surf zone profile: Proceedingsofthe10thConferenceonCoastalEngineering,p.504-524.StateofCalifornia,1966,PeoplevsKent Estate: California Appellate Reports (2d),p.156,160.StateofFlorida,1974,DepartmentofNatural ResourcesvsOcean Hotels, Inc.: Circuit Courtofthe15thJudicial CircuitofFlorida, Case No.7875CA(L)01Knott. Strahler,A.N.,1964,Tidal cycle changes inanequilibrium beach, Sandy Hook,NewJersey: Columbia University, DepartmentofGeology, OfficeofNaval Research Technical Report No.4,51p.Sunamura, T., and Horikawa, K.,1974,Two-dimensionalbeachtransformation duetowaves:inProceedings,14thInternational Coastal Engineering Conference,p.920-938.

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SPECIALPUBLICATIONNO.43Swanson.R.L..1974.Variabilityoftidal datums and accuracy determining datums from short seriesofobservations:U.S.DepartmentofCommerce, National Oceanic and Atmospheric Administration, National Ocean Service, NOAA Technical Report NOS64.41p.Szuwalski.A..1970,Littoral Environment Observation PrograminCalifornia,preliminaryreport,FebruaryDecember1968:CoastalEngineeringResearchCenterMiscellaneous Paper No.2-70,242p.Tanner, W. F.,1991,The relationship between kurtosis and wave energy:inProceedings, Ninth SymposiumofCoastal Sedimentology: Geology Department, Florida State University, Tallahassee,FL,p.41-50.___ 1992,3000yearsofsea level change: Bulletinofthe American Meteorological Society, v.73,p.297-303.Thorn,B.G., and Bowman,G.M.,1980,Beach erosion accretionattwotime scales:inProceedings,17thCoastal Engineering Conference, v. 1,p. Thompson,E.F.,1977,Wave climateatselected locations alongU.S.coasts: Coastal Engineering Research Center Technical Report No.77-1,364p.Thompson,W.C.,1987,Seasonal orientationofCalifornia beaches: Shore and Beach, v. 55,p.67-70.Trask.P.D.,1956,Changes in configurationofPoint Reyes Beach, California,1955-1956:Beach Erosion Board Technical Paper No. 91.27 1959.Beaches nearSan-----Francisco, California. 1956: BeachErosionBoard Technical Memorandum No.110.__ ---:::--_' and Johnson, J.A.,1955,Sand variationatPoint Reyes, California: Beach Erosion Board Technical MemorandumNo.65.__ and Snow,D.T.,1961,Beaches near San Francisco,19571958:UniversityofCalifornia, InstituteofEngineering Research, Report Series11,Issue23.U.S.Army,1984,Shore Protection Manual,CoastalEngineeringResearch Center, 2 vols,1272p.U.S.DepartmentofCommerce,1987a,Tide tables1988,high andlowwaterpredictions, east coastofNorth and South America including Greenland: National Oceanic and Atmospheric Administration, National Ocean Service,289p.___ 1987b,Tide tables,1988,high andlowwaterpredictions,westcoastofNorth America including the Hawaiian Islands: National Oceanic and Atmospheric Administration, National Ocean Service,234p.Urban,H.D.,and Galvin,C.J.,Jr.,1969,Pipe profiledataandwaveobservationsfromtheCERCbeach evaluation program, January-March1968:Coastal Engineering Research Center Miscellaneous Paper No. 369,74p.Watanabe,A.,Riho, Y., and Horikawa, K.,1980.Beach profiles and on-offshore sediment transport:inProceedings,17thInternational Conference on Coastal Engineering. v. 2,p.11061121.

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FLORIDAGEOLOGICALSURVEYWentworth,C.K.,1922,A scaleofgrade and class termsforclasticsediments: Journal of Geology,v.30,p.377-392.Ziegler.J.M., andTuttle,S.D..1961.Beach changes basedondaily measurementsoffourCapeCodbeaches: JournalofGeology, v.69,p.583-599.Zimmerman, M. S., and Bokuniewicz,H.J.,1987,Multi-year beach response along the south shoreofLong Island,NewYork: Shore and Beach, v. 55,p.3-8.APPENDIX: PROPAGA710NOFERRORSINCOMPunNG(compiled from formulations in Barry, 1978) Where R is the resultofsome numerical operation(e.g.,addition, subtraction, multiplication, division,powerfunction, average, etc.)formeasured quantities N N2 ,N3 ,...,Nn ,eachwithassociated measurement errors E1 ,E2 ,E3 ,..,En,respectively, then the total error Erorisapplied as: where Etorisdetermined according to:ADDITIONORSUBTRACTION EIr1I=0Je: + E; + + ...+ E; PRODUCTORQUOTIENTE ..=R ..... (;.) 28AVERAGE + + E; + ... + E; E ItJt -...!...-..:...-..---=:......---=..--_:,:,-,nCONSTANTERRORwhere E=E ,=E2=E3=...=En EIrJI'" E {n POWERwhere(R+E,}m=(N1+E1)m EhJI'"E.,11,""" ROOTwhere(R+E,}'/m=(N,+E,)1/mE -1 EItJt m1 N;

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SPECIAL PUBLICATION NO.43OPEN-OCEAN WATER LEVEL DATUM PLANES: USE AND MISUSE IN COASTAL APPLICATIONSbyJamesH"Balsillie,P.G.No.167 ABSTRACT Swanson(1974)notes that tidal datum planes".., are planes of reference derived from the rise and fall oftheoceanic tide", There are numerous tidal datum planes. Commonty used datums in the United States include the planes of meanhigh., high w.", (MHHW), mean high WMer(MHW),"""tide__(MTl),""""1wrJI(MSl).,.."low... (MlW), and",."/owei'lowWI (MllW).Eachdatumisdefined for a specific purpose or to help describe some tidal phenomenon.Forinstance, MHW high water datums havebeenspecified by cartographersinsome states(e.g.,Florida)asa boundaryofproperty ownership.lowwater datum planes havebeenusedasa chart datum becauseitisa conservative measureofwater depth and, hence, provides a factorofsafetyinnavigation. High water tidal stages have historicallybeenofimportance because they identified when sailors should report for duty when "flood tide" conditions were favorableforocean-going crafttoleave port, safely navigate treacherousebbtidal shoals,andputtosea.Not only do tidal datum specifications vary geographically based on localtoregional conditions for purposesofboundary delineation, cartographic planes, designofcoastal structures, and landusedesignations, etc.,butthey have changed historicallyaswell. Moreover, given ongoing technological advancements(e.g.,computer-related capabilities including the adventofthe personal computer),howweapproach these data numericallyishighly importan't from a data management viewpoint.INTRODUC710NTide gauges are usually locatedinwater bodies connectedtothe oceans, suchasestuaries and rivers, and may evenbeusedtorecord seichessuchasthose occurring in the Great Lakes. Here, however, the concern iswithopen oceantides. Openoceantidegaugesaredefined" ... asthosegaugessiteddirectlyupontheopenoceannearshorewatersand SUbjecttotheinfluenceofoceanprocesses,excludingthoseundertheinfluenceofinlethydrodynamics....(Balsillieandothers,1987a,1987b,1987c).Thelatterconstraintinthedefinitionisincludedeventhoughitisdifficulttodeterminetheextentofinfluencefrominlettoinlet. Open ocean tidaldatumapplicationsin29Florida are problematic becausethereare alimitednumberofgaugingstationstorepresentastronomicaltidalphenomena.Whileithas beenstandardpracticetolinearlyinterpolateopen oceantidaldatumsbetweengauges, such anapproachisnotrecommendedshouldthegauges bespacedfurtherapartthanabout6.2miles (Balsillie andothers,1987a).Ofthe33currentlyavailable open ocean gauges in Florida (Table 1),onlythree pairsofstationsmeetthisconstraint.Infact,theaveragedistancebetweenFlorida open oceantidegauges is27.4miles. Ostensibly,the6.2-mileconstraintisrecommendedsinceconcurrentlysimilar tidalstagedatumelevationscanvarysignificantlyoversegmentsofthecoastlinewhenthisdistance

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FLORIDAGEOLOGICALSURVEYTable.1. Tidal Datums and RangesforOpenCoastGaugesofCoastal Rorida(Updatedin1992after Balsilie. Carlen and Watters.1987a,1987b,1987c). OpenPlane MHHWMHW M1l. MLW MLLW Coordinates station Name CoastMTR XGauge Easting Northing (Feet) (Miles)I.D. (Feet) (F..t) (Ft.NOVO)FLORIDA EAST COAST Femanclina Beach 0061 362649.81 2287406.62 3.52 3.11 0.25 -2.61--5]2 5.831little Tabot Island 0194372355.76 2216450.20 3.60 3.30 0.55 -2.19 -2.35 5.49 19.753 JacksonviUe Beach 0291 377952.02 2163090.54 3.25 2.94 0.39 -2.17-2.33 5.11 30.150St. Augustine Beach 0587 417053.67 2008422.56 2.73 2.48 0.15 -2.17 -2.33 4.62 60.491Daytona Beach 1020498405.18 1779242.33 2.52 2.27 0.19 -1.88 -2.06 4.15 106.820Daytona Beach Shores1120511704.59 1749549.40 2.44 2.06 0.07 -1.89 -2.06 3.98 112.990 Patrick Air Force Base1727628785.91 1421930.52 2.272.09 0.32 -1.45 -1.61 3.54 185.030Eau Gallie Beach 1804619782.34 1383121.82 2.25 2.07 0.33 -1.33 -1.49 3.40 191.810Vera Beach 2105707153.65 1213218.30 2.01 1.89 0.19 -1.51 -1.67 3.40 227.560Lake Worth Pier2670 815854.41 829171.49 1.93 1.87 0.47 .0.93 -1.10 2.80 304.910 HUlsbo roInlet2862800981.65 700015.89 1.79 1.73 0.43 .0.87 -1.03 2.60 329.700 Lauderdale-by-the-Sea 2899797331.41 675151.18 1.99 1.93 0.63 .0.67 .0.83 2.60 334.580North Miami Beach 3050 789219.52 581194.67 1.77 1.71 0.46 .0.79 .0.96 2.50 352.520 MiamiBeach(City Pier)3170785173.29 522409.95 1.76 1.67 0.42 .0.84 -1.00 2.51 363.780NoTE;Xisthe shoreMnedistance in miles south ot the centertine ofSt. MillY's Entrance Channel (origin: northing=2317969.50 teel: easting =366516.31teet). FLORIDA LOWER GULF COAST Bay Port7151 291286.83 1527111.33 2.31 1.88 0]0.0.48 -0.97 2.36 4.472Howard Pm 6904241667.70 1389244.60 1.87 1.50 0.43 .0.64 -1.19 2.14 33.555 Clearwater6724231561.35 1325079.09 1.62 1.29 0.33 .0.64 -1.17 1.88 46.634 Indian Rocks Beach Pier6623224898.87 1295432.55 1.50 1.13 0.25 .0.63 -1.15 1.76 52.650St. Petersburg Beach6430261046.14 1218243.36 1.52 1.16 0.42 .0.32 -0.83 1.48 69.560Anna Maria 6243268746.05 1150335.15 1.52 1.20 0.45 .0.29 -0.76 1.49 83.284 Venice Airport 5858 352475.83 995445.81 1.35 1.07 0.36 .0.35 -0.84 1.42 117.918Captiva Island. South5383 351707.10179m.OO1.52 1.27 0.42 .0.42 .0.94 1.69 163.464Naples5110 563431.54 652958.84 1.81 1.55 0.50 .0.54 -1.172.09205.226Marco Island 4967589299.92 572441.43 1.96 1.71 0.56 -0.59-1.20 2.30 222.015NoTES:1.XisIhe shoretine distance in miles south of an arbitrarylocation inHernando County, FL. (origin: northing=1551271.53leet; easting=287952.53leet).2.State Plane Coordinates and distances arebased onZone3 lranstonnalionsWherenecessalY. flORIDANORTHWEST PANHANDLE COAST Dauphin Island 5180472269.39 871380.81 0.87 0.82 0.26 .0.29 -0.34 1.11 -33.347Gulf Shores1269467866.88 999712.52 1.20 1.13 0.50 {l.12 -0.18 1.25 -9.228 NaVlllTe Beach9678 508373.97 1254261.65 1.20 1.13 0.50 -0.14 .0.21 1.27 39.737Panama CityBeach 9189434604.55 1579274.67 1.25 1.18 0.54 -0.09 {l.14 1.27 104.489st.Andrews Park 9141 414248.96 1610651.22 1.16 1.06 0.47 .0.12{l.231.18 "1.489Mexico Beach8995 346061.53 1706517.15 1.06 1.00 0.41 .0.17{l.22 1.17 134.479 Cape San Bias8942 244076.07 1726862.581.010.99 0.30 -0.38 -0.38 1.37 162.615 Alligato r Point8261 325491.24 2035385.12 1.73 1.49 0.53 -0.44 -1.02 1.93 232.302Bald Point8237 344903.70 2050145.99 2.09 1.76 0.62 .0.52 {l.98 2.28 238.633NOTE: Xisthe shoreline distance in miles east01the AJabamalFlorida border (oligin: northing", 478050.00feet; easting .. 1047360.00feet). QENERAL NOTES:1. Tidal datums are referenoed to NGVD of1929. 2.Source of inlormation Bureau01 Survey and Mapping. Division01State Lands, Florida Department01EnVironmental Protection.lorthe National Tidal Dalum Epoch 01 1960-1978. 3.MLLW=mean lower low water. MLW =mean low water. MTL .. mean tide level, Which along the open coast = MSl = mean sea level: MHW =mean high water: MHHW= mean higher high water: MTR = mean rangeoftide Ve ..MTR= MHW MLW).30

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SPECIAL PUBLICATION NO.43isexceeded.Inaddition, it was found that linear interpolation led to results that simply do not reflect the natural behavior of coastal processes. Hence. in1987,a non-linear nth order polynomial numerical methodologywasintroduced and utilized to determine quantitatively open ocean tidal datumsfora significant portionofFlorida's ocean-fronting coasts (Balsillie and others, 1987a, 1987b,1987c).Updated results (Balsillie and others, 1998)areplotted in Figures1,2, and3.Thisworkisa companion papertotidal datums listingsforFlorida originally published by Balsillie and others (1987a,1987b,and 1987c) and updatedbyBalsillie and others (1998).Itwasdetermined necessarytoundertake the present compilation because of an increasing numberofmisapplicationsoftidal datums appearing in the coastal engineering literature. For example, Foster(1989,1991),Foster and Savage (1989a,1989bl,and Schmidt and others (19931 consistently usedMHWastheirvertical referencefromwhichvolumetric beach changes were measured. Komar (1998) usedNGVD(itisassumed that thisisNGVDof 1929, although suchisnot stated) but stated thatforhis siteNGVD....isapproximately equal to mean sea level'".Lee and others (1998) usedNGVDataNorth Carolina coastal location;theydid not state, however, howNGVDdeparts from MSLattheir site. These exemplify instances in which tidal datums referencing can introduce significantly compounded error. One illustrates other cases wherenoexplanation detailinghowtidal datums are appliedisgiven, and one cannot be sureifheorshe can have confidence in final results.Toone extent or another, misapplicationoftidal datums maybedueto8lackofunderstandingasto howtheyhave beenNorth South40050100150200250300350Alongshore Distance (statute miles) /..... IiIiI "Ii I,i i1 ..j i ,,,. "'"I)iIIi : i.--.;; !IiiI i I,IIi---'M:::iL : IIiIIT iI III L.VVI i II I MILW I! : i rI I : II II i! i i,II II c o 0.5>0 com-0.5 E-1 .3 -1.5 etlCl -2-2.5 -3 o4_ 3.5 o 3> c.!) 2.5Z2 S 1.5Figure 1. Relationshipbetweenopencoastdial datums and National Geodetic Vertical Datum of1929fortheFlorida East Coast. Alongshore distance is measured fromthecenterline ofSt.Mary's Entrance Channel proceeding southtoCape Rorida. (Updatedin1992after Balsillie and others,1987a).31

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FLORIDAGEOLOGICALSURVEYNorthSouth200o50100 150Alongshore Distance (statute miles) --,I!I !... IMLVV' 1 I ,I ...... ilAI -._-,,,-!I!II!IIo-1-1.5-2-2.5-3 -50 4 -,-,-------,-------------3.5+-i ,0-3 +1 >2.5 -.-1-----., __ ----'"""---_!':1.==C I g 0.51 ,MSlias >Q)W-0.5E .....aso Figure2.Relationshipbetweenopencoasttidaldatumsand National Geodetic Vertical Datum of1929fortheFlorida Lower Gulf Coast. Alongshore distance ismeasuredfrom northtosouthwiththeorigin locatedatthenorthendofPinellas County (i.e., north endofHoneymoon Island) and terminatingtothesouthatCaxambasPass. (Updatedin1992afterBalsillie and others,1987b).West East250o50100150200Alongshore Distance (statute miles)iIIIII i h W' ,.. i I I\fHVV I,. ...... ......",.,.MdN -IIPtA IIW! ..............."""'-i I;II,-0.5-1-1.5-2-2.5 -3 -503.5Cl 3> c.!J 2.5Z2 E.. 1.514 c o 0.5>0Q)wE ..... coCl Figure3.Relationshipbetweenopencoasttidaldatumsand National Geodetic Vertical Datum of1929fortheNorthwestPanhandle GulfCoastof Florida. Alongshore distance is measured fromtheFlorida-Alabama bordereasttoOchlockonee River Entrance. (Updated after Balsillie and others,1987c).32

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SPECIAL PUBLICATION NO.43established, andwhattheyrepresent. Thefirstpart of this work, therefore, discusses the history of tidal datums determination and definitioninU.S.coastal waters. Guidance illustrating proper tidal datums applicationsforcoastal scientists and engineersisavailableforimportant basic tidal datums applications (e.g., Cole,1983,1991,1997;Pugh,1987;Lylesandothers,1988;Brown and others,1995;Gorman and others,1998;Stumpfand Haines,1998).For other specific casesitisabsent. Verbal communicationsbyafewprofessionals reach only a small audience.Eventhen, thelatteroften results in a blank stare, leavingtheinstructorwiththe message that the explanation wasnotcomprehended by the informant,thatheorshe has predeterminedthatitisnot important,orthatthe informant has already predeterminedjustwhatis proper. The author has, therefore, in thelatterportionofthisworkpresented a seriesofselected examples and discussion about tidal datums applications.Atthe outset, one needstounderstandthatthe surveying profession,inlarge part,isconcernedwiththemanagementoferror and variability associatedwithhorizontal and vertical control. Itisoften the case that oneisnot convinced by simple directive that thereisa proper methodology, so evidenced by recent improper usesofdatumapplications in coastal engineeringworkscited above. This occurs because there isnothing to convince one that the methodology is better or bestatreducing error or variability. Therefore, the authorhasoptedtopresent a seriesofcommon improper tidal datums applications andtodemonstrate, relativetothe proper application,justwhy,numerically, they are inappropriate. INlETS/OUTlETS AND THE ASTRONOMICALTIDEThe preceding definitionofopen ocean tides excludes the influence of inlets (perhaps more appropriately termed outlets after Carter,331988.p.470). Hence, exclusionofinlets mightbeanoversight, particularlyinview of the current inlet management effort undertakenbytheState. At a most basic level, the classificationofinletsiswellknowndepending upon theeffectof astronomical tides relativetovolumeoffluvial discharge (e.g., van de Kreeke,1992).Infact,for many inlets, selectionofthe proper datum plane assists in providing a least equivocal representative designwaterreference level. Hence, a sectiononinlets astheyrelate to astronomical tides in Florida is herein developed.WATERLEVELDATUM PLANESInendeavors concerning hydraulic phenomena with a free fluid surface, many practitioners have lost perspectiveinselection of the reference fluid plane across which force elements propagate,inboththe prototypical setting andthenatural environment. Given this assertion, pemaps itwould be appropriate to review the basics of historical development of tidal datum plane quantification that has withstood the practicable tests of time. The first recorded effort of geodetic leveling in the United States beganin 1856p 57. During ensuing years surveying control become better. As chronicled by Schomaker(1981),by the first quarter of this century:Aherthepreviousperiodof com".rative/y short intetVlI1s between adjustments, 17 yeanelapsed beforethenetwork was adjusted IIgain. In the meantime,ithad become more extensive and complex, andincludedmany more SeHevei connections.TheGenerslAdjustmentof1929incorporllted75,159/emofleveling in the United Stlltes end,forthe first time,31,565km of leveling in Canadll. TheU.S.snd Canadian networkswere connectedby24tiesbetween Calais, Me./Brunswick,NewBrunswick;lindBlaine Wash.! Colebrook, British Columbill. A fixed elevationofzero

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FLORIDA GEOLOGICAL SURVEY WIIS IIssignedtothepointson mellnsell leveldetermined lit thefollowing26tide stlltions.Father Point, Ouebec St. Augustine, Ra. Halifax, Nova Scotia Cedar Keys, Ra. Yarmouth, Nova Scotia Ptlns8cola,Ra. Portland, Me. Biloxi, Miss. Boston, Mass. Galveston, Tex.Perth Amboy,N.J.'SanDiego, Calif. Atlantic City, N.J. San Pedro,Calif. Baltimore, Md. San Francisco, Calif. Annapolis, Md. Fort Stevens, Drs. Old Point Comfort, Va.Seattle,Wash. Norfolk,Va. Anacortes,Wash. Brunswick, Ga. Vancouver, British Columbia Fernandina,Ra.Prince Rupert, British Columbia 'Thers was no tide stationatPerth Amboy,butthe elevation of a benchmarieatPelth Amboy was establishedbylevelingfTomthe tide stationatSandy Hook. The 7929 adjustment provided the basis forthe definitionof elevations throughout the national ntItWork.. it existed in7929, and the resulting datumisstillused today.The elevation adjustment of 1929 was referred toasthe "Sea Level Datum of 1929", although it commonly became known as the "Mean Sea Level".Incoastal work, however, there are two standard Design Water Levels (OWls) that are applied. These and their definitions (GalVin, 1969) are: Mean Water Level (MWL) the time-averaged water levelinthe presence of waves, and Still Water Level (SWL) the time-averaged water level that would exist if the waves are stopped but the astronomical tide and storm surge are maintained. These water levels(i.e.,MWL and SWL) applyforany lengthoftime overwhicha field study or experimentisconducted, while MeanSeaLevel and other tidal datums are determinedasanaverageofmeasurements made over the 19-year National Tidal Datum34Epoch(i.e..the Metonic cycle; shorter seriesareappropriately named, e.g., Monthly MeanSeaLevel, etc.).Itwas not until1973thatthe confusion over theSeaLevel Datum or "MeanSeaLevel"asitpopularly cametobeknown and Mean Water Level was resolved by assigning the more appropriate nameof National Geodetic Vertical Datumof1929(NGVD) to replace Sea Level Datumof1929. NGVDof1929isadditionally defined (Harris, 1981)asa fixed reference adoptedasa standard geodetic datumforelevations determined by leveling.Itdoes not take into account the changing standsofsealevel. Because therearemany variables affectingsealevel, and because the geodetic datum represents a bestfitover a broad area, the relationship between the geodetic datum and local meansealevelisnot consistent from one locationtoanother in either time or space. For this reason NGVD should notbeconfusedwithmeansealevel, even thoughithas always been defined by a meansealevel (Schomaker, 1981). The various North American tidal datum planesaredefined(e.g.,Marmer,1951;Swanson,1974;U.S.DepartmentofCommerce,1976;Anonymous,1978;Harris,1981;Hicks, 1984)asfollows: National Tidal Datum Epoch the specific 19 year period adoptedbythe National Ocean Serviceasthe official time segment over which tide observations are taken and reducedtoobtain mean values for tidal datums. It is necessary for standardization because of periodicandapparent secular trendsinsea level. Itisreviewed annually for possible revision and mustbeactively considered for revision every25years. Mean Higher High Water (MHHW) the average of the higher high water heights of each tidal day observed over the National Tidal Datum Epoch. Mean High Water (MHW) the average ofallthe high water heights observed over the

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SPECIAL PUBLICATION NO.43National Tidal Datum Epoch. Mean Sea Level (MSL) the arithmetic mean of hourly heights observed over the National Tidal Datum Epoch. Shorter series are specifiedinthe name:e.g.,monthly meansealevel and yearly meansealevel. Mean Tide Level (MTL) 4 a planemidwaybetween Mean HighWaterand MeanLowWaterthatmayalsobecalculated as the arithmetic meanofMean HighWaterand MeanLowWater. MTL and MSL planes approximate eachotheralong the opencoast(Swanson,1974,p. 4). MeanLowWater(MWL) the averageofall thelowwaterheights observedoverthe National TidalDatumEpoch. MeanLowerLowWater(MLLW) -theaverageofthelowerlowwaterheightsofeach tidaldayobserved over the National Tidal Datum Epoch. Mean astronomical tide elevationsexhibitcyclic seasonal variability (Marmer,1951;Swanson,1974;Harris, 1981) and are included in tide predictions. Marmer(1951)notesthatseasonal variationintermsofmonthly mean sea levelfortheU.S.canbeasmuch as onefoot.Basedonthemanyyearsofmonthlydata, researchers (Marmer,1951;Harris,1981)note slight variations in the seasonal cyclefromyea r4to-yea r,butalso recognize the periodicityinpeaks and troughsovertheyears. For muchofourcoast,lowermean sea levels occur during the wintermonthsand higher mean sea levels during the fall. Harris (1981 ) inspected the recordtodetermineifstormand hurricane occurrence wasinanywayresponsibleforthe seasonal change, but found ... nosystematicvariability. Galvin (1988) reportsthatseasonal mean sea level changes arenotcompletely understood,butsuggeststhatthere appears tobetwoprimary causesforlowerwinter mean tide levelsfortheU.S.east coast:1)strong35northwestwinterwinds blow thewaterawayfrom shore, and 2)watercontractsasitcools.Henotesthatwindsaremore importantinshallowwaterwhere tide gauges are located, butthatcontraction becomes important in deeper waters. Swanson (1974) also notes ... seasonal changes resultingfromchangesindirect barometric pressure, steric levels, river discharge, andwindaffectthe monthly variability. Cole(1997)notes that seasonal variationintides is usually attributedtotwoharmonic constitutents: onewitha periodofone year termed the solar annual tidal constituent, and theotherwitha periodofsix months termed the solar semiannual constituent. Some consider thesetobemeteoroligical in nature, rather than astronomic. However, because the root causeofcyclic seasonal weather is the changing declinationofthe sun,theyshould more nearlybeastronomical in origin. Harmonic analysisofthe annual tidal record can easily determine the amplitude and phaseofeachofthese constituents, thereby providing a mathematical definitionofthe seasonal variation. (George M. Cole, personal communications.) Shorter-term changesoccurbi-weekly and monthly; longer-term changes occur in the relative levelsofland andseathat areofeustatic or isostatic origins(e.g.,Embleton,1982).Itis apparent, therefore,thatthere is natural variability associatedwithany average representationoftidal datums. Given these natural insensitivities associatedwithaverages,itis importantthatwedonotexacerbatethemthroughimpropermanifestationsofourownmakingwhenapplying tidal datumsasreferences.Atthis pointitis necessarytodefine certain terms. If one is interested in merely referencing a vertical distancewithouta requirementofspatial comparability, the result is termed a monergistiespp/icBtion. That is, the resultofthe application is good onlyforthat particular location. If, however, in addition to a vertical datum, one has a

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FLORIDA GEOLOGICAL SURVEYneed that the. resulting application will have spatial comparability(i.e.,it canbecompared to the same application at any other site), the resultisa synetgistic app/iclltion. Weshall discuss this latter class of application first.SYNERGISTICTIDALDAroMPlANEAPPUCA TlONSIthasbeenwidely recognized,asdemonstratedinthe introductiontothis paper, that selectionofthe proper tidal datum depends upon the purposetowhich itistobeapplied. The main purpose of this worK istodetennine the proper tidal datum for useincoastal science and engineering for referencing littoral forceandresponse elements.Forceelementsinclude astronomical tides, storm tides, nearshore currents, waves, etc. Responseelements include extreme event beachandcoast erosion, foreshore slope changes, long-term shoreline changes, seasonal shoreline changes, etc.Itbecame apparent during the courseofpreparation of this paper that determination of the proper datum planeisprobably best accomplished by discussing application/use examples.EXTREMEEVENTIMPACTFrom the preceding descriptionoftidal datu m planeswemust, from the scientific perspective,bequite carefulinselecting a reference water level from whichwedefine such response elementsasbeachandcoast erosion duetoextreme event impact,andsuch force elementsasthe peak combined stonn tide accompanying extreme events that,inpart, induces such erosion. As noted previously, water level datumplanes include certain insensitivities regardless of the rigorous natureofstatistical methods applied. It is necessary thatwedonot further exacerbate these insensitivities, creating additional variability and error through selectionofimproper reference datums. 36Asanexample, suppose thatweareanalyzingandinterpreting profile datatodetermine volumetric erosionofsandy beachesandcoastsduetoextreme event impact. Further, letusselectasour reference water level datumMeanHighWater,MHW.Thatis,weshall assess erosion volumes above MHW toanupland point that mustbecarefully deliberated depending upon whether the coastwasnon-flooded (interpretations are normally straightforward) or flooded and/or breached (interpretationscanbeproblematic)asdiscussedbyBalsillie (1985b, 1986).Itmustberecognized that MHWcanbeassigned the statusofa signature value for a particular locality, representing its National Tidal Datum Epoch. This assessmentcanbelevied becauseMHWcanchange significantly from locality-to-Iocality. For instance,inFlorida MHW variesfrom+3.12 feet MSL (or +3.36 feet NGVD; Balsillieandothers, 1987a) along thenorthemportionofNassau Countyonthe Atlantic east coast,to+0.66 feet MSL (or +0.90 feetNGVD;Balsillie and others, 1987c) along the westem portion?of Franklin Countyonthe northwestem panhandle GulfofMexico coastofFlorida. This embodies a potential maximum difference of almost 2.5 feetinMHW elevation about the StateofFlorida. Suppose that for the above two areas, profile conditions are comparable. Furthermore, suppose that extreme events embodying precisely the same magnitudesandcharacteristics producing identical force elements impacted the two areas, resultinginidentical response elements, thatis,the same erosion volumes(i.e.,theareaabove the dashed linesandbelow the solid linesofFigure4).If, however,wereference the erosion volumes to MHW (shaded areas)asillustratedinFigure4,8.12cubic yards of sand per footareeroded above MHW along the northern portion of Amelia Island,33per cent less than the 12.05cubic yardsofsand perfooteroded above MHW along western St. George Island. It becomes quite clear, therefore, that erosion volumes around the state cannotbecompared using MHW, since the MHWbaseelevationisnot only

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SPECIAL PUBLICATION NO.43LONGER-TERMBEACHRESPONSESMHWisnot the proper referencewaterlevel datumtoapply for erosion volumes.Italso becomes apparent thatitisnot proper tousethe datumforreferenceforsuch a force elementasthe peak combined storm tide. Similar logic results in the conclusion that useofthe MHHW, MLWiand MLLW datum planes would alsobeimproper.Itshould,infact.beclearthatMSL (or MTL) is the only tidal datumthatistobeusedforreference.-eas.IeNot1MmAIMIIeI.-rd,......,County,lIIiW'" +3.12 rtMSL Q. '"yct3/M ,.I I .... 6 .. 12 :; 2 o2 0 IISl .-:.. 10 ....j \;:/:.!............_eo*-............DimnCetram1MIISlInten:ePt("'1)Agare 4. &osion volumes. 0..above MHWfor identicalproIIesimpacted by identical stormevents.butwith clfferent Ioc* MHWplaDes.geographically variable, but significantly so. Onewillnotefurtherthat,forother North AmericanMHWdatums(seeTable 2), theproblemcanbecomeevenfurtherexaggerated. Infact.ithasbeen demonstratedthatMSListhe best datumfromwhichtoreference erosion volumes; ...atthe seaward extremityofthe poststormprofile, some materialofthe seaward sink (also including some degreeofpost storm beach recovery) may reside above MSL (determinedtobeabout6%ofthe seaward sink volumefrom245analyzed profile pairs), the analytical methodisfairly unbiased sinceitis applied equallytoall profiles investigated" (Balsillie,1986).Seaward datumsordepthofprofile closure are not suitable references,ifonly because survey responseisslowcomparedtothe responseofsubaqueoussandsizedsediments in the energetic force element surf environment(e.g.,Pugh,1987;Lyles and others,1988).It becomes apparent, therefore,thatIt is clear why the MSL datumisthe desired convention to apply for extreme event impacts to which force and response elements are tobereferenced. MSL datum should alsobeapplied to longertermforceandbeach responses. Notwithstanding the need for a standardized convention already required for extreme event impact, thereissound reasoning that it applies to longerterm scenarios, although, such application is more subtle than for the extreme event impact case. The preceding extreme event impact scenario has dealt with physical beach and coast conditions of a sort which transcend certain physiographic limitations. That is, the energetics associated with storms andhurricanesso exceed physical stability constraints that individual gradients comprising the beach and coast(e.g.,shoreface, foreshore slope, berm(s), duneorbluff stoss slope; see Figure5)do not, in themselves, impose limiting conditions. Under normallittoralforceconditions,however,physiographic slope characteristics become more nearly a limiting condition. Perhaps the most importantofthese gradientsisthe foreshore slope, a subjectthatneeds some discussion prior to addressingtwoadditionalsynergisticapplication/useexamples,namely, seasonal beach changes and long 37

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FLORIDA GEOLOGICAL SURVEY Table2.Selected North American Datums and Ranges ReferencedtoMSL (after Harris,1981).ISt.tionIMHHWIMHWINGVDIMTLIMLWIMLLWIMTRIEastport,ME9.328.88-0.20-0.10.01 -9.4118.20Portland,ME4.87 4.45-0.220.00-4.46-4.808.91Boston, MA5.164.72-0.31-0.15-4.86-5.199.58Newport,AI2.181.93-0.23+0.15-1.69-1.753.62New London,CN1.48 1.22-0.43-0.10-1.34-1.452.60Bridgeport,CN3.61 3.31-0.54-0.05.36-3.526.70Willets Point,NY3.853.59-0.58-0.05.58-3.787.10New York,NY2.512.19-0.49+0.05-2.29-2.424.50 Sandy Hook,NJ2.66 2.33-0.510.00-2.34 -2.474.60Breakwater Harbor,DE2.462.04-0.41-0.05.08-2.154.10Reedy Point,DE3.072.73-0.35-0.10-2.77-2.855.51Baltimore, MD0.740.51 -0.43 -0.03-0.52-0.641.03Washington,DC1.541.39 -0.54 0.00-1.37-1.422.76Hampton Aoads,VA1.411.22 -0.02 +0.03-1.22-1.262.44Wilmington,NC2.26 2.02 -0.38 +0.02-2.24-2.334.26Charleston,SC1.882.87 -0.05 +0.21-2.67-2.815.17Savannah Aiver Entr.3.773.38 -0.28 -0.15-3.56-3.706.94FLORIDA Listed it T.bIe1.Mobile, AL0.730.65 -0.05 -0.05-0.62-0.701.27Galveston,TX0.570.47 -0.10 -0.05 -0.44 -0.850.91San Diego, CA2.902.11 -0.21-0.05 -2.09-3.06 4.'-0 Los Angeles, CA2.631.91-0.080.00-1.87-2.823.80 San Francisco, CA2.592.04+0.06+0.30-1.93-3.144.00Cresent City, CA3.222.56-0.120.00-2.49-3.755.10South Beach,OA3.222.56 -0.49 +0.02-3.09-4.486.30Seatle,WA4.833.94-0.350.00-3.75-6.487.60NOTES:MfA= Mean rangeoftide; averege valueofMfLis-0.01feet MSL; average valueofNGVD(1929)is-0.29feet MSL; these stations do not necessarily represent open coast gauging sites.termbeach changes. The foreshore slopeorbeach face slope (Figure 5) is definedbythe ShoteProtectionManual (U.S.Army,1984)as" ...thatpartofthe shore lyingbetweenthe crestoftheseawardberm (or upperlimitofwavewashathigh tide) and ordinarylowwatermark,thatis ordinarily traversedbythe uprush andbackwashofwavesas tides rise and fall. Komar(1976)elaboratesfurther, statingthatthe foreshore slope"...isoftennearly38synonymouswithbeachfacebutiscommonlymore inclusive, containing also someofthe beach profilebelowthe bermwhichis normally exposedtothe actionofthewaveswash.The bermorbeach berm is the ... nearly horizontalpartofthe beachorbackshore formedbythedepositofmaterial by wave action ... some beaches have no berms, others have oneorsevera'" (U.S.Army,1984).The berm and foreshore (or beach face) are separatedatthe berm crest or berm edge.

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CHUoloreBotro'" Neon'If,.e Inshore or Shore foeeThe slopeofthe foreshore tendstoincrease withanincreaseinthe grain size of the sediment (U.S.Army,1933;Bascom,1951;King,1972).Dubois(1972)foundaninverse relationship betweengrainsizeandforeshore slope where the foreshore sediments contain appreciable quantitiesofheavy minerals. Sediment porosityandpermeability effectsonthe foreshore are discussedbySavage(1958).GeneraJly,foreshore slope increaseswithanincreaseinnearshore wave energy(allother factorsheldconstant),andaninverse relationshipisfoundwhenwave steepness is applied(e.g.,Bascom, 1951; Rector, 1954; King, 1972).Forinstance, steeper eroding waves suchaswinter waves will resultinflatter foreshore slopes, while longer (less steep) accretionaIY waves suchaspost storm or summer waves produce steeper slopes. Average foreshore slope statistics for FloridaarelistedinTable 3. While this treatmentofforeshore slopesisgeneral,it39 Figure 5. BeachplCllfiIerelatedterms (fromU.S.Amy,1984). "wffor ... th6tportion ofthe beach or coastthllt is, on a daily basis, subject tothe combined influenceofhighlindlowtides,lind Wave activityincluding waveupl1JshOfbackwash. For purposesofthis Chllpter,itincludes thlltpatt ofthe beach between mean higher high wsfer (MHHW) and meanlowerlow wllter (MUW). SPECIAL PUBLICATION NO.43In Florida, the foreshore slopeisdefined (Chapter 168-33, Florida Administrative Code, StateofFlorida)as:The slopeofthe foreshore, the steepest portion of the beach profile, is a useful design parameter since along with thebermelevation it determines beach width(U.S.Army,1984,p.4-86).Asa response, element the foreshoreisa function of force elements suchasastronomical tides, waves, currents, and property elements suchasgrain size. sedimentporosity,andsediment mass density.

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FLORIDA GEOLOGICAL SURVEYTable3_ Aorida Foreshore Slope Statistics byCountyandSurvey.County Survey Type Survey Date n Average Standard Slope Deviation FLORIDA EAST COAST Nassau Control LineFeb1974810.03590.0235Nassau Control Line Sep-Oct 1 981850.04740.0344Duval Control Line Mar1974680.01990.0178St. Johns Control Line Aug-Sep19722030.05230.0322St. Johns Control Line Feb-May19842100.03390.0384Flagler Control Line Jul-Aug1972990.10770.0273Volusia Control Line Apr-Jun19722270.03480.0306Brevard Control Line Sap-Nov19722170.07980.0413Brevard Control LineAug1985-Mar19862190.07190.0347Indian River Control Line Nov 19721160.11630.0335Indian River Control Line1986 119 0.12010.0793St. Lucie Control Line Jun19721150.10120.0358St. Lucie Condition Jan-Feb1983360.09190.0248Martin Control Line Oct-Nov 19711150.09390.0378Martin Control Line Jan-Feb1976960.08670.0287Martin Control Line Feb-Apr19821040.08450.0301 Palm Beach Control Line Nov 1974-Jan19752260.10110.0347Palm Beach ConditionAug1978240.1113 0.0334Broward Control Line1976-19761270.10990.0423Dade Condition Nov 1985-Feb1986280.12430.0328Total nand Weighted Averages2,5150.07600.0359FLORIDA LOWER GULF COAST Pinellas Control Line Sep-Oct 19741850.07470.0447Manatee Control LineAug1974670.10090.0419Manatee Control LineAug1986670.09420.0377Sarasota Control Line Jun-Aug19741810.09830.0375Sarasota ConditionApr1985620.10510.0469Charlotte Control LineMay1974670.07570.0343Charlotte Control Line Dec1982680.11270.0363LeeControl LineFeb19742380.08430.0415LeeControl Line May-Sep19822360.09800.0419Collier Control Line Mar-Apr19731440.07960.0265Collier Condition Sep1984400.09270.0277Total n and Weighted Averages1,3550.09030.0389FLORIDA NORTHWEST PANHANDLE COAST Franklin Control Line May-Jul19731470.09330.0349Franklin Control Line Jun-Sep 1 9812440.11550.0472Franklin Condition Oct1982310.07690.0322Gulf Control Line Jul-Sep1973 610.10320.0540Gulf Condition Jan1983450.07850.0327Bay Control LineFeb1971-Feb19731410.0707 0.0255Walton Control Line Oct19731300.09910.0699Walton Control Line May 19811300.10600.0578Okaloosa Control Line Nov-Dec1973490.06500.0406Escambia Control Line Jan-Feb19742130.09880.0429Total n and Weighted Averages1,2190.09700.0458Grand Total nand Weighted Average5,0890.08480.0391INOTE:n =0 numberofprofiles per survey.,40

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-_.:. SPECIAL PUBLICATION NO.43 -10-40 -20 "'10:----MSL51.'tt. Like Figure 4, Figure 6 is a simplification,IIII III --...."""""""-----...'.!.'-------3 --,.0::;:----.;-'MSL.-------.l ,, 40tt. -IBalsillie,1998).Here,however,beachwidthis used since, comparedtothe others,itoffersthe largest range in magnitudes.Letusinvestigate such seasonal changesfortwolocalitieswithidentical profileconditionsand average seasonal MSL shoreline variations,butdifferentMHWdatums.First, however,weneed some representative foreshore slope data. From Table3,letusselect the average foreshore slopeoftanafs=0.085torepresent awinterforeshore slope and amaximumoftanafs=0.2(i.e.,0.085+3 standard deviations)torepresent asummerforeshore slope. Thetwocases, eachwitha summerandwinterprofile are illustrated in Figure6. ....... --17.1fL --""1 100 1010 WINTER -.nil" = 0.085 CASEIIMHW=+4.0fl.MSLWINTER a.II..'"0.085 CASEIMHW=+2.5ft.MSL12041o-2 ...-I +2 +I +2 '"'Il:""'""---MHW---l"""--MIL g+I...... = +4 : +2 iii 0 .....,,-+4 +2_0 """ en::E... i of -40 200Distance (feet)Figure6. Seasonal horizontalshorelneshiftanalysis.will suffice for the following use/application examples. Seasonal BeachChangesBeach changes due to extreme impacts from storms and hurricanes are considered to more nearly represent isolated events. There are, however, beach changes that are more nearly episodic or cyclic. For instance, systematic beach changes through an astronomical tidal cycle(e.g.,Strahler,1964;Sonu and Russell,1966;Schwartz,1967),cutand fill associatedwithspring and neap tides(e.g.,ShepardandLaFond,1940;Inman and Fil/oux,1960),andeffectsofsea breeze(e.g.,InmanandFilloux,1960;Pritchett,1976),arewellknown.Ofthe possible cyclic occurrences, however, perhaps themostpronounced isthatoccurring on the seasonal scale. Using the above prescribedrules,thefollowingscenarioscanbesuggested. During thewinterseason,whenincidentstormwaveactivityismostactive,high, steepwavesresult in shoreline recession. Normally,theberm is erodedandagentleforeshore slope is produced. Sandremovedfromthe beach isstoredoffshorein oneormore longshore bars. Duringthesummerseason smallerwaveswithsmallerwavesteepness values transport the sandstoredin longshore barsbackonshore, resulting in awiderbeach berm andsteeperforeshore. Seasonal beach changes have been described intermsofsand volume changes,contourelevation changes,andhorizontal shorelineshiftorbeachwidthchanges (see

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FLORIDAGEOLOGICALSURVEYalbeit representative since the slopes and distances presentedareprecise. First, letusfocus our attentionontheCASEI locality whereMHW=+2.5feet MSL. Onewillsee thatifweutilizeMSlasthe reference datum, the seasonal variability in beachwidthshiftsby40feet. If, however, one usesMHWasthe reference datum, theshiftis56.9feet. Thetwovalues departfrom.each otherby30per cent. If,onone hand, the CASEIlocality weretobesingularly assessed using the MHW reference plane shoreline, consistent results would emerge. If,ontheotherhand, one wouldwishtorelate force elements (e.g., wave and tide characteristics)tothe shoreline response, theuseofMHWwould pose problems (more about this later). Similar assessmentforthe CASE/Ilocality(MHW=+4.0feetMSl)results in a departureofthe MHW -MSlshoreline changeof40per cent. AsforCASEI,application results similarly apply.Nowletus compare the resultsofshorelineshiftatthetwolocalities.MSlshorelineshiftswould remain comparable from localetolocale, since they directly represent both the tide base and surf base.MHWshoreline shifts, however, departfromeach otherby15 per cent. Again,aswithextreme event impact, MHW shoreline shifts can notbecompared from localitytolocality (the samewouldhold trueforother datums suchasMHHW,MlW,MllW,etc.). Infact,ifweevaluated seasonal beach changes volumetrically,MHWoranyofthe other site specific variable datums would result in precisely the same non-comparability problemsoftheextreme event example previously given.Long-TennBeach Changeslong-term beach changes pose some highly important concerns. Profile type surveys provide a source of detailed coast. beach, and nearshore conditions. Such data 42 offertheopportunity for calculationofvolumetric changes which, if sufficient alongshore profiles are surveyed, allows for sediment budget detenninations. Profile surveying for temporal beach changes, however, requires a monument system maintained over many years. For instance, Florida's coastal monument system has beeninplace for some26years. Other such efforts occurona site-specific basis. For most of our coasts thereisinsufficient monumentation,orithas notbeeninplace for enough time to assure long-term records. Even the26years fortheFlorida program is not lengthy. Moreover, early surveys measured shoreline positions.Inorder to obtain volumetrics from shoreline position data, horizontal shoreline change (.boX) and volumetric change (.bo V)have been related in the ShIItePtrIteetionMaIlUlll (U.S.Army, 1984) according to: where cisa relating coefficient.Ifnotverycarefully applied, suchanapproach can produce highly misleading results (Balsillie, 1993a).long-termshoreline change rate dataforFlorida (Balsillie and Moore, 1985; Balsillie,1985f,1985g; Balsillie, and others,1986)are determinedfromshoreline position dataforthe periodfromabout1850to present. Commonly uptoabout a dozen data points are available fromwhichto conduct temporal analyses. Bywayof example, letusinspect the applicationofMHWasthe reference datum planefordeterminationofhorizontal shoreline change.letusselectanaverage MHW valueof+1.7 feetMSlandamaximum valueforMHWof+3.0feetMSl,bothofwhich are representative of Florida conditions (from Table 1). Using these data, three casesofcombinations of MHW and foreshore slope values are illustrated in

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--....--SPECIAL PUBLICATION NO.435040302010o -.......::----MSl (SURF BASE)-----4 -10, ,II I I: ..10.2ft.: processes.THESURFBASEThe preceding application/use examples, while rigorously identifying inconsistencies resulting from the use of extreme datum planes for coastal science and engineering purposes, have not specifically addressed coastal processesinterms of the forces that cause beach responses.Inordertounderstand how the sillbase applies, one needs a basic understandingofhowwavestatistics are derived and applied.Ata givenwaterdepth a woretrain is a near-periodic setofwaveswitha characteristic average wave crest heightH,wavelength L. period T, and having aCASE3 ,-"alaso0.016 4r---------r-------------. 3o CASE 1 Berm'a"a,.'"0.085 2 WfW .. ---------1 2 ... I MHW =+1.1It -------.j I I CASE 2I :--''''ftlana,. =0.2; 0 (StR:BASE)----i I III I .........""+3.0 It _+o 2 31 ...HI Figure7. shorelne shift analysis. Figure 7. Additional data could have been selectedaswellasadditional combinations; however. the threeillustratedcaseswillmore than sufficeforour purposes. The profilesofthe three examples are plotted sothatthe MSL (Surf Base) intercepts define the originsofthe plotsthattheymaybecompared. Horizontal differencesofMHWintercept locations are identifiedbyvertical dashed lines. Deviations range from10.2to25.6feet, allofwhichare significant illustrating the inappropriate natureofusingMHWforsuch a purpose. Again, aswithextreme eventimpactand seasonal shoreline change,MHWshoreline shifts are not comparablefromlocalitytolocality (the same would hold trueforother datums suchasMHHW, MLW, MLLW, etc.).Infact,ifweevaluated long-term beach changes volumetrically,MHWoranyofthe other site specific extremal variable datums wouldresultinpreciselythesame non comparability problemsofthe extreme event and seasonal shorelineshiftexamples previously given. We can approach the subject from adifferentperspective.IfMSL is not used as a reference Surf Base plane, thenwhatshouldbeused?Ifone selectsanextreme tidal datum plane such as MHW, doesitrepresent a base towhichaktological force and response elements canbebased? Doesithave spatial continuity?Isitapplied in a conceptually correct sense? Allofthese questions needbedirected toward coastal43

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-_.. FLORIDA GEOLOGICAL SURVEYspecific directionofpropagation. Wherewaterdepthsaresuch that waves remain relatively stable, the wave record (suchasthat measured by a wave gauge) will represent all wave trains(i.e.,multiple trains) passing the gauge. Multiplewavetrain height and period measurements are termed the speetTalwavereconl or wave field. Shote-brea/dng waves, however, do notconformtospectral wave statistics. This occurs becauseinnearshore waters, waves are ultimately limited bywaterdepth accordingtodb=' ,.28 H b (McCowan,1894;Balsillie, 1983a; Balsillie,1999b;Balsillie and Tanner,1999)where H b is thewavecrest heightatshore-breaking anddbis thewaterdepth where thewavebreaks. Hence, shore-breaking waves engendermomentwavestatisticsfor singletrains since a wave trainwithlargerwaveswillbreakfurtheroffshore than onewithsmallerwaves.Itfollows,then,thatmomentwavestatisticsvarydepending uponwhethertheyrepresent the spectralwaverecord or single shore-breaking wave trains. Themostcommonlyapplied nearshorewaveheight statistics are the averagewaveheight H, root-mean-squarewaveheight Hrms' significantwaveheight H s (averageofthe highest30per cent wavesof record). H10(averageofthe highest10percentwavesofrecord) and H1(averageofthe highest 1 percentwaves). Eachofthese moment measures is applied in the designofcoastal engineering solutions by defined prescription. Relatingmomentmeasuresforspectral and shore-breaking wave cases are listed in Table 4toillustrate the variabilityofrelatingcoefficients. Letuslookatanexampleoftide conditionstowhichwemight superimpose certainwaveconditions. Figure8illustrates6daysofanastronomical tide record. Suppose one inspects the case whereMHWand H s are,forwhatever reason(s). selectedforuse. From the plots, each peakofthe44tide mightbeconsidered tobemaintained, say.for1/2to1 hour. Doubling this value, sincetwohighs occurineach tidaldayforthe semidurnal tide, then MHW is actually maintainedforabout 4 to 8 per centofthe time (e.g.,14and 28 days a year). Superimposed upon MHWisthe significant wave height which, by definition, neglects70percentofthe wave record (assuming that H s adequately includes any significant zerowaveenergy component; Balsillie, 993b). Clearly, suchanapplicationwouldbeinappropriateforone applying such force elementstoannual or long-term conditions. Unfortunately, however, such misapplica tions,ofwhichthis isjustone example, are commonplace.Onthe other hand, such an application might have more viable applicationifitincluded a storm surge(i.e.,peak combined storm tide minus the astronomical tide) to represent the peak combinedstormtide and attendantwaveactivitywhichoccurred coincidentwiththe peak astronomical tide. This latter case, however, has application onlytoidentifya conservative design elevationfora structure (e.g., perhaps a pier)whichis a monergistic tidal datums application, but certainlynottoprofile response which constitutes a synergistic application. Previously discussed use/application examples have already ledtothe eliminationofextreme datum planes (i.e., MHHW, MWH, MLW, MLLW)ashasthe preceding example, and MSL andNGVDremainforconsideration. TheNGVDreference is not,ofcourse, a tidal datum.Itis rather,forall practical purposes a geodeticdatumforcomputational reference,thatalthoughforopen-coast gaugeshasa departure generally less than0.5ofa foot from MSLforFlorida, the longterm primary departureofMSL andNGVDis subject to influencesofsea level rise or fall (shorteHerm natural deviations have been discussed above). Hence,itshouldnotbeutilizedasa datum, particularly where global data are involved(i.e.,where the non-tidal vertical reference

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SPECIAL PUBLICATION NO.43Table4.MomentWave Height Statistical Relationships(afterBalsllie andCarter.19848.1984b).Portionof Wave Record Spectral Relationships Shore.Breaking Relationships Considered All Waves Average WaveAverage Breaker Height "H Height= It AllWavesH=0.885 HrmsIt =0.98 ftHighest30%H=O.625 It =O.813 Hbs Highest 10% H=-O.493 f(o =O.73 Highest 1 % H=-0.375 f( =O.637 ,"" Definitions: Average WaveRoot WaveN W'=significant Height =H= 1 Height =-Hrms wsve height N.N.,NOTE:Formulas applytoboth H and HH,o.and H,arecalculated using the formofthe equationasforthe average wave height.represents a conceptual planenotlocated and/ornotcalculated suchthatitisnotnecessarily comparabletoNGVD). The remaining tidaldatumis, then, MSL.Otherthanitsidentificationbyeliminationofotherdatums,thereare strong motivating reasonswhyMSLis the proper tidaldatumreferencetousewhendealingwithcoastal processes(i.e.,forceand response elements).Aswehave already learned, principalforceelements include astronomical tides,stormtides, andwaves.Astronomical tides are,bydefinition,already accountedforwhenusing MSL, andstormtides are extreme events thoughaccountedforas described in the preceding section. Waves.however,constitutean ubiquitous phenomenon nearconstantin nearshore coastalwaters(exceptforcoastswitha substantial zerowaveenergycomponent).45Therefore,bythe processofelimination MSL is defined as the sudbase (it is also the tide base,nottobeconfusedwiththeconceptofthe wavebase). Upon inspectionofFigures 1,2,and 3,itisreadily apparentthatMSL, like the other datums, has variability.Why,then,wouldweselectitas a conventionforreference?Waterlevels arenotglobally coincident in the vertical senseforvery real reasons. However, MSL is a measure representativeofthe entire distributionofthe metonic astronomical tide, and is the only oneofthe tidal datumsthathas statisticalcontinuityand comparabilityofresultsfromplacetoplace. Notingthatforopen coastalwatersMSL is equivalenttoMTL (Swanson,1974,p.4), then the MTL measure remainstorepresent the central tendencyofthe tide distribution since metonic measuresofhighs andlowsare used in its determination. The

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FLORIDA GEOLOGICAL SURVEYoneshouldviewitinthe statistical sense whereweknow more about its central tendency thanwedo about the behavior of the lower foreshore (corres pondingtoMLW or MLLW) or higher foreshore (corresponding to MHW or MHHW). Whenweapproach the extremes of theslope,exceptionsduetophysiographic irregularities can occur. Hence, one needstoview the surf base foreshore slope intersectionasa focal point about which the foreshore rotates. In this context, the focal pointisdirectly relatedtoincoming force elements. Furthermore,itisconceptuallynotsubjecttovariationstowhichthe upper and lower partsofthe foreshorearesubject, sinceitis an origin both common and comparabletothe focal pointatother localities. From a slightly differentviewpoint,oneargumentFigure8. SelDiciumai tideCUlVesfor6 tidal_ys(froID proffered by a colleaguewhoManner,1951).took the "devit's advocate" position,isthatthe MHW intercept represents the most stable portionofthe foreshore slope. While this may appear appropriatetothe layman,fromthe geological perspectiveitis not.Itis, infact,the least stable in termsofrepresenting a normal slope. The most stable position of the foreshore is probablyatthe MSL intercept (Le., relativetoother submerged portionsofthe profile) sinceitisreflectiveofaverage, ongoing force elementstowhichitismodifiedasa response element. By comparison, the foreshore in the vicinity of the MHWorMHHW intercepts is affected only during high tide stages and canbereflectiveofextremal impacts(e.g.,storm wave events). Extreme impacts affecting the MHW foreshore are likelytoresult in relict featureswhichpersist until continual average force conditions finally issue becomes particularly poignant from inspectionofFigure1where the behavioroflowwaters(i.e.,MLWand MLLW) and high waters(i.e.,MHWand MHHW)areanythingbutsymmetrical intheirrelationshiptoMSL (or MTL), signifying a needforanaverage surf base measure. Statistically extreme average point measures providing numerical valuesofupper(i.e.,MHWand MHHW) andlower(i.e.,MLW and MLLW) tidal datums are robustly founded. Corresponding extremesofsuch physiographic featuresasthe foreshoremaynotbeso robustlyfounded,sinceitsformationandmaintenance has not been rigorously defined in termsofforces and responses(e.g.,Kraus and others,1991,p. 3). Given the manner inwhichwecurrently define the foreshore,46

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SPECIAL PUBLICATION NO.43return the upper portionsofthe slope to normal slope status.Whatpoint estimatorofwave parameters, representing the appropriate force element, does one subscribeforanextremeaveragemeasureoftheastronomical tide, sayforMHW?Onedoesnotapply such point estimatorsforwave transformation synergistic applications, because none wouldbeappropriate. Hence, unless an averagesealevel(MSlor MTL)iscombinedwithanaverage wave height, one is mixing apples and oranges.Itisimperative when undertaking such a task,werender the tasktosimplest terms. For instance, when transforming wavestothe pointofshore-breaking, including anywavereformation and rebreaking, the waves shouldbeexpressedasan averagewaveheight or, perhaps, root-mean-squarewaveheight since these measures include allwavesofrecord.Donotuse the significantwaveheight, averageofthe highest10percentofheights, averageofthe highest 1 percentofwaveheights, etc. Whetherornota significant zero wave energy component is included dependsonthe purposeofthework(Balsillie, 1993b).Anyconversionofthe averagewaveheighttoextreme wave height measuresofTable4,sayfordesign purposes,isaccomplishedbyconverting the average measure, butonlyafterwavetransformationasanaverage height has occurred. Kraus and others (1991) note the importanceofthe averagewaveheight andtoutits usetobethe ... Rosettastoneforconversion...., no less important is the proper applicationofthesurfbase (MSL)whichbecomes the Rosetta Stoneforreferencing tide andwavephenomena.Anothergood reasonforusing averages throughout any numerical transformation processisbecause oneisoften unabletodeterminefrompublished resultsifthetransformationmethodologyistrulycommutative.MSL is, therefore, the only datum47planethatisrelevant to the surf base. For a relatively short experiment or field study,MWLorSWL references are suitable to represent the time frameofthe experiment or study. Such referenced results, however, maynotbecomparable to results referenced to MSLatother localities. For this reason, all applicable datums ... MSL,MWl,and SWL, where known ... collectively termed DesignWaterLevels (OWLs), shouldbeprovided in documentationofresults.SEALEVB.RISESofar,wehave butinpassing mentioned the effects of sea level rise, recalling that the primary difference between NGVD and MSL (or MTL) is sea level rise.Inanhistorical context, the effect of sea level riseonthe current metonic period has. thus far, been insignificant from a surveying perspective.Itsfuture effect. however. remains controversial(e.g.,Titus and Barth(1984)and Titus (1987) versus Michaels (1992),tomention butonlyseveral published works among avastnumber on the subject). Otherworkindicates detailsofsealevel reversals or pulses (Tanner,1992,1993),also characterizedascrescendos (Fairbridge, 1989). There are certain applications where temporal specificationsofsea level rise areofpotential consequence. Hence,froma data management and processing viewpoint,itbecomes in certain cases necessarytostartwithNGVD and calculate the relative date-certainsealevel rise component. The result,ofcourse, becomes the date-certainMSl(or MTL). For the1960National Tidal Datum Epoch, the following relationship assessed in British Imperial unitsisposited: MSLD NGVO+c(D 1969.5)where MSLoisthe date-certain valueforMSl(or MTL),C = 0.0060forFlorida's east Coast), c=0.0064forFlorida'sLowerGulf Coast, andc=0.0069forthe Florida

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FLORIDA GEOLOGICAL SURVEYPanhandle Gulf Coast (Balsillie and others,1987a,1987b,and1987c,respectively), and 0isthe survey date. Please notethatthe valueofc changeswithtimeand location; thecurrentvalueofcfora particular coast is a representative regression value.MONERGISncTIDAL DA TUM PLANE APPUCAnONSThus far,theabove application/use examples have been describedassyner gistic.Thatis, horizontal shorelineshiftand volumetric change results are referencedtoa datum sothattheycanbecompared spatiallywithinaNorthAmerican or globalcontext.Thescientificneedtodo so has been robustlydemonstrated.Even more, considerable analyticalworkis requiredtodeterminesuch synergistic resultswhichcannotbesimplyrecalculatedtoanother datum. As described intheintroduction there are, however,otherquitedifferentconcep tual applicationsofastronomical tidaldatumplanes. Someofthese arenotnecessarily boundbytheneedfora spatial tidaldatumconvention. These are describedasmonergistic applications. The purpose, here, istodemonstrate several such examples.DESIGNSOFFITELEVATIONCALCULATIONS"Soffitelevation"is a generictermmeaning the elevationtotheundersideofthelowestsupportingstructuralmember exclud ing the pilingfoundation,say,fora pier or singleormuti-familydwelling. Such elevations are calculatedforextreme elevations associatedwiththeimpactofextreme events(i.e.,stormsand hurricanes). The goal istoraisethestructuretoan elevation sothatitis above thedestructivehydraulicforceelementswhichwillpassbelowthesoffitand through the piling foundation. For a pier,forinstance, a peak48combined storm tide (super-elevatedwaterlevel including contributionsofwindstress, barometric pressure decrease, dynamic wave setup and astronomical tides) correspondingtoa 50-year return period elevationisnormally usedfordesign calculations. Superimposed uponthestorm tide stillwaterlevel is a designwaveheight, normally a breakingwaveheight correspondingtoHb10orHb1.As previously noted, where awaveshore-breaksisdependent on thewaterdepthwhich, in turn, is dependent on patternsofsediment redistribution occurring during event impact. Sediment redistribution is largely afunctionofoffshore sedimenttransportand longshore bar formation (Balsillie,1982a,1982b,1983a,1983b,1983c,1984a,1984b,1984c,1985a,1985b,1985c,1985d,1985e,1986;Balsillie and Carter,1984a,1984b,etc.).Anexampleis illustrated in Figure 9. Such designworkcalculations are site-specific because resultswillbeinfluencedbythepre-impactsite-specific profile configuration. There is no intention, noratthistimea needtocompare such resultstoother localities. Should suchanapplication need arise(e.g.,a generalized modelingeffortor an accounting needtoassure consistency in design application(s)),thenthe reference base shouldbeMSL. However, suchtransformationstootherdatumscanbeeasily accomplished, comparedtomuchmore involved re calculationofsynergistic data (Le., volumes or horizontal distances).EROSION DEPTH/SCOUR CALCULATIONSSite-specific designworksuchasminimumpileembedmentrequiresknowledgeofthe design surface elevation. This elevation necessarily includes erosiondepth(e.g.,longshore bartroughelevation or beach erosion elevation), additional scour caused by the pile, and sediment liquefaction.Inessence these design elevation calculations are treated in the samemannerasdesignsoffitelevation

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SPECIAL PUBLICATION NO.43 Damaged Section --t--Destroyed Section --o-i 40 .2 10 iiiiQ 30> 20 __ __ --.Lt _.-'-':::.::.:'" ._ ::-.:::::::::::::.::-.:'.::':.:-:.:.:::::.l1I:__ -...ST SWL,....---------...,,!r---::::'-''-'-'-.-.oPot Storm -=-;;.-r-:-::_-=. .....-_-. -"'''''.''=--. --.---.---.--.--.-_-.-_-.-_-._---s--'Prof".-._._.-._._-_.-._._.-'-'-'_.-'-'-'-'Pre-Storm Profle ._.-.--_. -".,7' _.-.._.Bar 'D'oughEnveIope---"'" -.-. ........ DistancefromNGVD Shotelne(feet) Agure9.ActualdamagetotheRagler Beach PierfromtheThanksgiving HolidayStormof1984 (Balsilf.e. 1985c)usedtotesttheMultiple Shore-Breaking Wave Transformation Computer Modelforpredictingwavebehavior. longshore bar formation. and beachlcoast erosion (after Balsillie.1985b).calculations.SEASONAL HIGHWATEACALCULAnONSIn addtiontoshort-term erosiveimpactsduetoextremeevents, our coasts aresubjecttolong-term changes. In1972,theStateofFloridaincorporatedconsiderationofstormlhurricaneerosion inaffixingthelocationofCoastalConstructionSetbackLines. In1978,itadopted a posture inwhichquantitativeextremeeventerosion becametheprimarymeansbywhichCoastalConstructionControl Lineswerelocated.Itwasnotuntil1984,however,thatlong-term erosionwasofficiallyrecognizedbytheStateofFlorida (Balsillie and Moore,1985;Balsillie,StateofFlorida (Balsillie and Moore,1985;Balsillie,1985f;1985g;Balsillie and others,1986;etc.,).In1985,theGrowthManagementAmendmentrequiredassessmentoferosionatany coastal siteforwhichapermitapplicationwastenderedtobe assessedfora30-yearperiod.Associatedwith30-yearlong-term erosion projections isthelocal Seasonal HighWater(SHW)defined as ...the line formedbythe intersectionofthe rising shoreandthe elevationof150percentofthelocalmean tidal range abovelocalmean highwater...(para.161.053(6)(a)1,F.S.).Thatis:SHW=(1.5MRT)+MHWinwhichMRT isthemean rangeoftide(commonlyreferredtoasthemeantiderange). Onemightassumethatthe30-yearerosion projection istobeassessedattheSHWelevation. This issimplynottrueand, infact,aswehave seen earlierwouldbe a misapplication leadingtospatialdiscontinuityintroducing computational error (Balsillie and Moore,1985).Rather,theerosion projection needstobe assessedatMSL. The, requiredmethodologyspecifiedbyrule (para.16B-33.024(3Hhl,F.A.C., republishedasStateofFlorida,1992,62B33.024(3)(h)1.,F.A.C.) specifies NGVDastheassessment elevation. The original rule,however,waswrittenbefore compilationofdatumelevations, foreshore slope, and sea level rise informationfortheState. SubsequentworkIBalsillie, Carlen, and49

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FLORIDA GEOLOGICAL SURVEYWatters. 1987a.1987b, 1987c)hasremedied the situation, and theruleneedstobereassessed. Followingisanalternative for consideration. from the figures that only the upper east coastissignificantly affected by the SHW, attesting to thelowimpact figure of Curtis and others (, 985).BEACH-COAST NICKPOINT aEVA nONBOUNDARYOFPUBUCVERSUS PRIVATEPROPERTYOWNERSHIP IISL----I-BNdI.....,..-+-1.. _-The boundary between private(i.e.,upland) and public(i.e.,seaward) beach ownershipisnormally fixed by some commonly applied tidal datum. For mostofthe U.S.this boundaryisdetermined by the planeofMHW whichwhenitintersects the beachorcOast forms the lineofmean highwater.However, unlike other riparian ownership determinations(i.e.,fluvial, lacustrine and estuarine), littoral properties must, in addition, contendwithsignificantwaveactivitythat seasonally varies. Hence, ocean-fronting beaches all too often experience cyclic seasonalwidthchangesofa magnitUde long recognized as problematic in affixinganequitable boundary (Nunez,1966;Johnson,1971;O'Brien,1982;Graber and Thompson,1985;Collins and McGrath, 1989). ---------JI:)"-" -_ .. ----DI.ne or IIIuff......---Coatzf 10EAST j ... i1: LOWERGULF COAST I 000.10.20.30.40.50.80.70.80.9 EJrc....1Ce PFigure10.Beach/coast niekpoint elevations for Aorida. Inreality, SeasonalHighWaterisa misnomer. First, the components necessary for computation are metonically derived(i.e.,1 9-year averages). Second, the results have notbeendemonstratedtorepresent seasonal variation in astronomical tide behavior. Third,ithasbeen demonstrated that upon application, only about13%to15%ofundeveloped beach property in Florida wouldbeaffected by the SHW application (Curtis and others,1985).An alternative considerationforsuchanapplication, and others,isthe beach/coast nickpoint elevation. The nickpoint represents the point where the beach intersects the coast, normally identifiedasthe baseofa dune or bluff. Generation and maintenanceofthe nickpointisprimarily a functionofdirect extreme event impact. These elevationsforFlorida areprobabilisticallyinvestigated; the results are plotted in Figure10.Median(i.e.,50thpercentile)nickpoint f elevations, Ne ,forFlorida areasfollows: 1) East :. Coast:+7.15feet NGVD (1929), 2) Lower Gulf Coast:+5.65feet NGVD (1929), and 3) Panhandle Gulf Coast:+6.45feetNGVD (1929). The relationshipbetweennickpointelevationsandSHWelevationsforFlorida is illustrated in Figures 1 1, 12. and 13.Itisapparent50

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SPECIAL PUBLICATION NO.43 PALMBEACH BREVARDSHW ---------------------MedlIn Ne ij 5 w -00100 200300 400...... )Figure11. eom,.risonofSeason ... High Wmer (SHW) and MecillnBeach/CoastNickpointBevatioa (NJfor theRoridII East eo.st.u. iI 0 IldE I, e.illrJI 5...,.,.-....... N. S"_ i 5---------------------------iiiSHWo ............L.J o100200 DIst8nce(min)Figure 12. eom,.risonofSeasoal High Wider (SHW) and MecIiInBeach/CoastNickpointBevnon (N.)forthe RoridIILower Gulf CoIIst. 51200o IoNIc c !2 I !ci BAY GU.FFRAtLJNC1;en III-L.... Ne-----------------------------_.._-------.--/--I.Io j 5 I 100 D6stIInce("...)Figure 13. eom,.risonof Seasonal High Water (SHW) and Mecian Beach/CoastNickpoint 8evation(Ne )forthe Aorida Panhancle Gulf COiIst.

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FLORIDA GEOLOGICAL SURVEYMany investigatorshavesuggested that the legal boundary for ocean.fronting beaches should notbecontinuously movingwiththe seasonal changes, but shouldbethe most landward or "winter"lineof mean high water (Nunez. 1966). Selectionofthe "winter" MHW line wouldbethe most practical to locate and wouldbethemostprotectiveofpublic interest by maintaining maximum public access to theshore(Collins and McGrath. 1989),InFlorida, the ocean.fronting legal boundary seasonal fluctuation issue was deliberated uponinState of Florida, Department of Natural ResourcesvsOcean Hotel, Inc. (State of Florida,1974)asit relatedtolocating the MHW line fromwhicha 50-foot setbackwastoberequired. JudgeJ.R.Knott rendered the following decision:Thiscoufftherefore concludes thllt thewinterlind most IlIndwllrd mean high wllter linemustbe selectedliS theboundllry between the stlltelUJd theup/lind owner.In so doing thecouff hilS hlldto bMlInce thepublicpolicyfllvoring prlvllte littorlllownership IIgainst thepublicpolicyofholdingthetidelllnd intrustforthe people, wherethe preservation of II vital publicright issecured withbut minimMeffect uponthe interests oftheuplllndowner.A 1966 California Court of Appeals decision rejected the application at a continuously moving boundaryinPeoplevsKent Estate. However,nodecisionhasbeen renderedastowhat linetouse (Collins and McGrath, 1989). More recently, Collins and McGrath (1989) report:TheAttomey Generlll's Officein Clllifomill hilSoffereditsinformlll opinion thllt, ifsqullrely fllced withthe issue, ClIlifomill courtswouldfollowthe rellsoning in the52Floridll ClIse lind IIdopt the "winterlindmost Ilmdwllrd lineof melln hightide"liSthe leglll boundllry betweenpublictideJlInds lind privllteuplllnds ...(itshould be understoodthlltsuch1Iboundllry,whichreilltive/y stllble, would not be permllnently fixedbutwouldbe IImbullltory tothe extent there occurs long-term IIccretion orerosion).Theuseof the MHW datum plane for the determinationofa boundaryisstraightforwardly a monergistic application; one mustbecareful, however,tonote that determinationofthe seasonal shoreline shift (or beach width)isnot. This will require a synergistic application using MSL. Similarly, any periodic review and boundary relocation duetolong-term shoreline changes will require the synergistic approach.INLETSAND ASSOCIATEDASTRONOMICAL nOES It hasbeenspeCUlatedthat tidal inletscansignificantly affect the characterofopencoast tide behavior. Thereare,however, insufficient alongshore data crossing inlets, both upcoastanddowncoast, upon whichtoassesstheeffect of inlets (termedthe"shadow effeer). Inaddition, flow characteristics varyfrominlettoinlet and a multitude ofsuchinvestigations wouldbereqUiredtoinvestigate the alongshore influence of inlets. There are, however, some isolatedopencoasttidedata near inlets or within inlet throats closetotheshoreline. There aremoredatainteriortoinlets.Suchinformation for 24 Florida tidal inletsandpasses are plottedinFigure 14fromwhich some significant elucidating conclusions maybegleaned. ThedataofFigure14are displayedintenns ofthemeasuredinlet tide data minus theopencoasttidedataof Balsillie and others (1987a, 1987b,1987C).Inthiswaythe

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SPECIAL PUBLICATION NO.43 53reference planefora synergistic application (e.g., storm impact, seasonal,orlong-term beach changes), the amountoferror introducedispotentially highly significant.Itwould,inaddition, occur over a quite short segmentofshoreline.ForMHW,39%ofthe data are acceptable (i.e., liewith :t 0.1ft.ofthe open coast data)with61%ofthe data being unacceptable. For MLW76%ofthe data are unacceptable. However,forMTL almost70%ofthe data are acceptable. Thisshiftin data acceptabilityforMTL is not aberrant. Rather,itistobea moderating expectation since MTL is the plane lyinghalfwaybetweenMHWand MLW and should, therefore much more closely approach open coast MTL values than anyofthe otherextremaltidaldatumplanes .Therefore,dependingontheapplication, the locally measured MSL (MTL)datumplaneorthe open coast MSL (MTL)datumplane shouldbeusedforsynergistic applications in the vicinityofinlets (whichisused shouldbeclearly specified). Hence, MTL (or the MSLsurfbase) is, once again, the proper datum planetouseforinlets.Infact,O'Brien (1931)intentionallyincludedinhisdefinitionsfortidal characteristics (e.g.,flowarea, tidal prism)thattheybereferenced specificallytoMSL. Ideally, the alongshore "shadoweffect"ofinlets on astronomical tides shouldbequantitatively assessed. Suchworkis, however, expensive and time consuming andisnot expectedtobeforthcoming any time soon.Itisalsoofsignificance to notethatCole(1997,p.38) has foundthatnth order polynomial equations precisely determine tidal datums within estuaries. The orderofthe bestfitpolynomialforanestuary was MHWI MLW f------------_--------------..0.2 .. .. -0.6 ........ ,__ -'__ --.I", __ --L1'L....-_..:.HI:.:.lI o0.5 1.0 1.5 2.0 2.5 ...fromSftoreIIne0.2fi------------------------o.' ... _1.1..._ ..... : -0.4i-0.8l. -0.1 ; .0 iif e.2 :IO.2f->, .Ii-,.... --------------------------O'i 0.4,.....---..L..---'---........--"'-----4 o U 0.2MTl c .M_-, -----.-r ----------Q, O.I. c. i! 0.1 t5 0.6" 0.4 Aggre 14. Oep8rtureofRoridaMt tide data andopen coast tide Uta (measured tidedata fromDNR, Bureau of Surveyand Mapping). See textfor clscussion. acceptability of the data within the dashed lines (i.e., plus and minus 0.1 ft.) canbeeasily assessed. DataforMHHW andMLLWplot similartoMHWand MLW datawithsomewhatgreater variability, and arenotshown. ThefirstconclusiontobedrawnfromFigure 14, isthatthe amplitudeofthe tide is attenuatedbythe inlet (i.e., MHW becomeslowerinelevation andMLWgains elevation); this is illustrated in a different mannerfortwoFlorida inlets in Figure 1S.Hence,ifone were(asbefore) to use MHWasthe

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FLORIDA GEOLOGICAL SURVEY __ _ 2.00 I I I I I I : :: I I ,. I I 6" I 1,,.-.... 1.00 --!--,--.. i --r ---r : "'" I tl II '-"'t i' 'i I il I I J I 10 I g 0.00i '"_:_'_-\-aI I \\ > Q) ....,..1i1.".J .,'W\,' -I'to L _-1.00"\' --", -Io I I "D I t:I I I I I-200.,.1'. ".,1." ".11.""'",I"1""".,1",,,,"1"",,,,(.0.0010.0020.0030.0040.0050.0060.0070.00Time (Hours) Rgure 15.Open oceanandinside astronomical tidesfor Ft. PierceandSt.LucieInlets, Aorida (fromAnonymous,1992).foundtobepredictable based on the lengthofthe estuary and the travel speedofthe tidalwavewithinthe estuary.CONCLUSIONSA considerable amount of information, hopefully simplifiedasmuch as possible, has been presentedinthe above application/use examples. It would not serve further purpose to restate conclusions here that couldbemore succinctly touted, other than to state that MSL (or open-coast MTL) is the proper datumtoemploy for synergistic coastal engineering applications. It is hoped that this work has rendered it apparent that how we perceive and treat such subject matterina scientific context is sensitively critical. The considerations presented herein embody not just philosophy, but engender intellectual contemplation and deliberation necessary to arrive at a deductive, reasonable, and robustly correct convention for application.Inthis day and age, itisunfortunate that while we are finally realizing such enhanced data processing capabilities, we are fraught with misapplication that all-too often render good data to inaccurate results.ACKNOWLEDGEMENTSReviewofthisworkbyselectedstaffofthe Florida Geological Survey is gratefully acknowledged,inparticular those editorial contributionsofJacqueline M. Lloyd, Thomas M. Scott, Kenneth M. Campbell, JonArthurand Walter Schmidt. Review by the BureauofBeaches and Coastal Systemsisalso acknowledgedwithspecial thanks to RalphR.Clark and Thomas M. Wattersfortheir interestinthe subject and/or editorial comments. Special thanks are extendedtoGeorge M. Colewhoreviewed the manuscript and encouraged its pUblication.REFERENCESAnonymous,1978,Definitionsofsurveying and associated terms:Jointcommitteeofthe American Congress on Surveying and Mapping and the American SocietyofCivil Engineers,210p.____,1992,St. Lucie Inlet manage ment plan: Applied Technology and Management, Inc., Gainesville,FL.54

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SPECIAL PUBLICATION NO.43BalsillieJ.H., 1982a, Offshore profile description using the power curvefit,PartI:explanation and discussion: Florida Department of Natural Resources, Beaches and Shores Technical and Design Memorandum No. 82-1-1,23p. ,982b,Offshore profile description using the power curve fit, PartII:standard Florida offshore profile tables: Florida DepartmentofNatural Resources, Beaches and ShoresTechnicaland Design Memorandum No. 82-'' ,.7'p.,,983a,Onthe determinationof----whenwavesbreak in shallow water: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No.83-3,25p.,1983b,The transformationof----thewaveheight during shorebreaking: the alpha wave peaking process: Florida DepartmentofNatural Resources, Beaches and ShoresTechnicaland Design Memorandum No. 83-4,33p.____,1983c,Wave crest elevation above the designwaterlevel during shore-breaking: Florida DepartmentofNatural Resources, Beaches andShoresTechnicaland Design Memorandum No. 83,41 p.____,1984a,Wave length and wavecelerityduringshore-breaking:Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 84-1,17p.55____,, 984b, Attenuationofwavecharacteristicsfollowingshore breaking on longshore sand bars: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 84-3,62p.1984c,Amultiple shorebreakingwavetransformationcomputer model: Florida DepartmentofNatural Resources, Beaches and ShoresTechnicalandDesignMemorandum No. 84-4,81p.____,, 985a, Redefinitionofshore breaker classificationasa numerical continuum and a design shore breaker: JournalofCoastal Research, v. "p.247-254.____,1985b,Calibration aspectsforbeach and coasterosionduetostorm and hurricane impact incorporating event longevity: Florida DepartmentofNatural Resources, Beaches and ShoresTechnicalandDesignMemorandum No.85-',32p. _____ -"1985c,Post-storm report: the Florida East Coast Thanksgiving Holiday Stormof21-24November1985:Florida DepartmentofNatural Resources, Beaches and Shores Post Storm Report No. 85-1,74p.1985d,Post-storm report: HurricaneElenaof29Augustto2September1985:Florida DepartmentofNatural Resources, Beaches and Shores Post-Storm Report No.85-2,66p.

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FLORIDA GEOLOGICAL SURVEY1985e,Verificationofthe MSBWT numerical model: coastal erosionfromfourclimatological events and littoral waveactivityfrom three storm-damaged piers: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 85-2,33p.1985f,EstablishmentofmethodologyforFloridagrowthmanagement30-yearerosionprojection and rule implementation: FloridaDepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No.85-4,79p.1985g,Long-term shoreline change ratesforGulf County, Florida: afirstappraisal: Florida DepartmentofNatural Resources, Beaches and Shores Special Report No.85,42p.,1986,Beach and coast erosion----duetoextreme event impact: Shore and Beach, v.54,p.22-37.____,1993a,Relationship between shore-normal horizontal shorelineshiftand volumetric beach change: Florida DepartmentofNatural Resources, DivisionofBeaches and Shores Memorandum. 1993b,LowerGulf Coastof---------Floridawavedata its useasa design force element andforsediment budget determinations: FloridaDepartmentofNatural Resources, DivisionofBeaches and Shores Memorandum. ,1999a,Seasonal variation in----sandy beach shoreline position and beachwidth:Florida Geological Survey, Special PublicationNo.43.p.1-29.56____' 1999b.Onthe breakingofnearshore waves: Florida Geological Survey.155p.Balsillie,J.H., Carlen,J.G.and Watters. T.M..1987a,Transformationofhistorical shorelinestocurrent NGVD positionforthe Florida East Coast: FloridaDepartmentofNatural Resources, DivisionofBeaches and ShoresTechnicaland Design Memorandum No.871.177p.1987b,Transformationofhistorical shorelinestocurrent NGVD positionforthe Florida Lower Gulf Coast: Florida DepartmentofNatural Resources, DivisionofBeaches and Shores Technical and Design Memorandum No.87-3,141p.1987c,Transformationofhistorical shorelinestocurrent NGVD positionforthe Florida Panhandle Gulf Coast: Florida DepartmentofNatural Resources, DivisionofBeaches and Shores Technical and Design Memorandum No.87,152p.____"1998,Open-oceanwaterlevel datum planesformonumented coastsofFlorida: Florida Geological Survey, OpenFileReport73,92p.Balsillie,J.H.,and Carter,R.W.G.,1984a, Observed wave data: the shore breaker height: Florida DepartmentofNatural Resources, Beaches and ShoresTechnicaland Design MemorandumNo.84-2,70p.____, 1984b, The visual estimationofshore-breakingwaveheights:Coastal Engineering, v. 8,p.367385.

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SPECIALPUBLICAliONNO.43Balsillie,J.H., and Moore,B.D.,1985,A primer on the applicationofbeach and coast erosiontoFlorida coastal engineering and regulation: Florida DepartmentofNatural Resources, Beaches and Shores Technical and Design Memorandum No. 85-3,37 p.Balsillie,J.H., O'Neal, T. T., and Kelly, W.J.,1986,Long-term shoreline change ratesforEscambia County, Florida: FloridaDepartmentofNatural Resources, Beaches and Shores Special Report No.86-1,84p.Balsillie,J.H., and Tanner,W.F.,1999,Stepwise regression in the earth sciences: a coastal processesexample:EnvironmentalGeosciences, v.6.Bascom,W.N., 1951, The relationship between sand size and beach-face slope: Transactionsofthe American Geophysical Union, v.32,no. 6. Brown,C.M., Robillard,W.G., and Wilson, D.A.,1995,Brown'sboundary control and legal principles,NewYork,Wileyand Sons, Inc.,410p.Carter,R.W.G.,1988,Coastal Environments, London, Academic Press,617p.Cole,G.M.,1983,Waterboundaries, Rancho Cordova, Calfornia, Landmark Enterprises,67p.,1991,Tidalwaterboundaries,----'StetsonLawReview, v.20,p.165-176.,1997,Waterboundaries,New----'York,Wileyand Sons, Inc.,193p.Collins,R.G., and McGrath,J.,1989,Whoownsthe beach? Finding a nexus gets complicated: Coastal Zone'89,v.4,p.3166-3185.Curtis, T. D., Moss,R.L.,and Shows,E.W.,1985,Economicimpactstatement: the 30-year erosion rule: FloridaDepartmentofNatural Resources, Beaches and Shores Economic Impact Statement No.852,84p.Doodson,A.T.,1960,Mean sea level and geodesy: Bulletin Geodesique, v. 55,p.69-77.Dubois,R.N.,1972,Inverse relation between foreshore slope and mean grain sizeasafunctionofthe heavy mineral content: Geological SocietyofAmerica Bulletin, v.83,p.871876.Embleton, C.,1982,Mean sea level:inM.L.Schwartz, ed., The EncyclopediaofBeaches and Coastal Environments, Stroudsburg, PA, Hutchinson Ross,p.541-542.Fairbridge,R.W.,1989,Crescendo events in sea-level changes: JournalofCoastal Research, v. 5, p. i-vi. Foster,E.A.,1989,Historic shoreline changes in Sarasota County, Florida:inTanner,W.F., ed., Coastal Sediment Mobility, Florida State University, DepartmentofGeology, Tallahassee,FL,p.31-40.____,1991,Coastal processes near Cape San Bias, Florida: A casestudyusing historic data and numerical modeling:inProceedingsofthe 1991 National Conference on Beach Preservation Technology, p.400411.57

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