Migration of swash zone, step and microtopographic features during tidal cycles on an estuarine beach, Delaware Bay, New Jersey, U.S.A.

Abstract

A time-series analysis of changes in surface elevation on the foreshore of an estuarine beach was conducted to compare movement of topographic features in the swash and breaker zones with results derived from study of ocean beaches. Wave heights on the upper foreshore during the field study averaged 0.15 m, with an average period of 2.4 s. The average height of the beach step was 21 mm. Smaller elevation changes, up to 12 mm in height, occurred at 10–15 min periods. There were more small elevation changes, greater longshore variations in these changes, and greater variation in the form of the beach step during the rising tide than during the falling tide. The variation in the small elevation changes and the beach step are attributed to greater short-term fluctuations in beach saturation during rising tides, causing greater variability in the velocity of swash and backwash.