Field study of the effects of storms on the stability and fate of dredged material in subaqueous disposal areas.

Dredged sediment placed on the bottom of the Long Island Sound is subject to dispersion by the tidal stream, estuarine circulation, waves, and disturbances of the hydraulic flow field by storms. The tidal stream is the dominant source of energy for the resuspension and transport of sediments; waves do not contribute significantly to dispersion in water depths greater than 60 ft. Random fluctuations in the water velocity are detected at all depths. During a storm fluctuations in velocity increase in intensity and are important agents of sediment resuspension. Direct, wind-driven flow over the bottom is weak, but storm winds cause water level increases up to 3 ft. above the usual tidal level. The energy available for sediment transport is then greatly increased. Repeated bathymetric surveys of a deposit of dredged material at the New Haven disposal site show that after initial self-consolidation of the mound, no significant changes in pile configuration occurred over a three-year period, erosion of the deposit is not detected. The data obtained show that to best contain silt-clay dredged material, the disposal site should be on a naturally accreting mud bottom, the disposal operation should emplace a large volume of material on the site expeditiously, and the deposit should be built to an optimum configuration. (A.)