ABSTRACT
Ten beach profiles across a 9 mi section of straight coast in the vicinity of Jones Beach, New York have been surveyed about 10 times per year since the great storm of March 1962. The study area, on the south shore of Long Island, has a restricted fetch from the west, is generally open to waves from the south and east, and is near the western (downdrift) end of a net longshore transport system.
The nominal beach slope, defined as elevation over distance between the front dune crest and the mean sea level (MSL) intercept, is 0.10 at the eastern boundary of the study area and decreases unevenly to 0.018 at the western boundary. The elevation of the upper limit of scour, and the foreshore slope, are greatest for the steep profiles. The elevation of maximum sand loss during storms has a tendency to be higher for the first storm following a period of accretion and to decrease with succeeding storms.
Two extensively studied storms in February 1972 appear to have moved large quantities of sand in opposite directions. On 4 February 1972, a storm deposited 45,000 yd3 of beach material above −3 ft MSL on the eastern one-third of the study area while eroding 285,000 yd3 from the western two-thirds. Two weeks later another storm of similar intensity removed 365,000 yd3 from five eastern profiles and deposited 48,000 yd3 on the five western profiles. These data suggest that gross longshore transport rates in this area are much greater than net rates. In each storm, the amount deposited above −3 ft MSL was approximately 15 percent of the total quantity eroded. The indicated direction of net transport during each storm correlates well with the principal wind directions during that storm.
Such areal and temporal changes in beach profiles, if not anticipated, can affect the success of beach nourishment programs or the stability of protective shore structures. Data developed in this beach profile study may assist designers 280on these problems. For instance, the envelope of beach profiles on Jones Beach had a maximum horizontal extent exceeding 650 ft, and a maximum vertical range of 12 ft. Such data are useful in siting and designing groins. Similarly, the indicated reversing transport direction affects areas of deposition and erosion, and thus must be considered in positioning structures and in the location of feeder beaches.
