From and migration of sand waves in a large estuary, Long Island Sound

Abstract

Sand waves occur in eastern Long Island Sound with heights up to 4 m and lengths to 100 m. The waves do not form if either more than 10% mud or 12% coarse sand is present in the sediment. Mud suppresses wave formation by increasing the cohesion of the sediment. Sand-wave shape is independent of the water depth, d, provided the sand-wave height, H, is smaller than 0.86 d 1.19. Both symmetric and asymmetric wave forms are present. Observation of the migration of sand waves by repeated bathymetric surveys indicates a net sand flux greater than 0.01 cm 3 cm −1 sec −1 in the direction faced by the steep slopes of the waves (i.e. westward, into the Sound). Under this sand flux, waves more than 30 cm high will not be measurably altered by a reversal of the semidiurnal tidal current.