. Beach and inlet changes at Ludlam Beach, New Jersey. Beach erosion; Coast changes; Littoral drift. a. Wave Effects. The most important factor in developing the geometry of a beach, and in the sand movement from or onto the beach, is the waves which act upon it. At Ludlam Beach there appears to be a direct temporal relationship between the relative volume of sand above MSL and the frequency of waves greater than 4 feet in height (see Fig. 16). Waves exceeding 4 feet at the Atlantic City gage were often associated with storms. The steepness (wave height/wavelength at the gage) of a 4-foot wave
. Beach and inlet changes at Ludlam Beach, New Jersey. Beach erosion; Coast changes; Littoral drift. a. Wave Effects. The most important factor in developing the geometry of a beach, and in the sand movement from or onto the beach, is the waves which act upon it. At Ludlam Beach there appears to be a direct temporal relationship between the relative volume of sand above MSL and the frequency of waves greater than 4 feet in height (see Fig. 16). Waves exceeding 4 feet at the Atlantic City gage were often associated with storms. The steepness (wave height/wavelength at the gage) of a 4-foot wave with an 8-second period is This steepness value is assumed to designate the cutoff point between waves causing erosion and those causing accretion. However, caution is recom- mended when using this value. Saville and Watts (1969) for example, pointed out although bounding wave steepness values between and are commonly used, these values are derived mostly from laboratory studies and are of doubt- ful accuracy when applied to a field situation. Monthly changes in sand volume are directly related to the monthly wave power reaching the beach, as shown in Figure 65. Beach volume changes are from Figure 33. Five years of wave data (1962-67) and 10 years of survey data (1962-72) were averaged to obtain Figure 65. The figure supports the assumption that waves with an 11-second period and less than 4 feet high cause beach accre- tion. For the North Sea coast, Schijf (1959) observed a relationship between winter gales and summer swell, and their effect on beaches, which was similar to the accretion-erosion changes observed at Ludlam Beach. 1-5. Jan. Feb. Mar. Apr. May June July Aug. Nov. Dec. (Mo) Figure 65. Monthly wave power of waves exceeding 4 feet in height reaching the Atlantic City shore, showing the relationship between wave power and beach volume change. 80. Please note that these images are extracted from scanned page images that may have been dig
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