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
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