Distribution of surface pebbles with changes in wave energy on a sandy estuarine beach

In Delaware Bay, NJ, dissipation of wave energy on the low-tide terrace increases as water levels become lower, creating a spatial gradient in wave energy delivered to the foreshore. Two experiments using dyed pebbles as tracers document increasing quantities of pebbles with distance downslope on the beach, corresponding to the decreasing energy gradient. There is a second locus of high pebble concentration near the upper limit of swash at high water. There is sufficient sand in the backwash of low-energy waves to bury pebbles; they project into the flow of the swash and have low pivoting angles, increasing the probability of entrainment and movement over the sand particles to the upper limit of swash. -from Authors