Use Of Sediment Transport Calculations In Dredged Material Disposal Site Selection

Identification of suitable sites for ocean disposal of dredged material is an ongoing problem for federal agencies, local port authorities, and users of marine resources. One of the considerations in site selection is dispersion of dredged material away from the site, either during disposal operations, or afterward. No formal technique for evaluation of sediment dispersion among candidate sites in the initial stages on site selection has been proposed. This paper presents a method for quantitatively comparing in situ dredged material stability over a large area as an aid in the identification of regions that may contain suitable candidate sites. The method was applied to site selection studies conducted for the U.S. Environmental Protection Agency (EPA) in the New York Bight. were made on a coarse grid representing the New York Bight using bathymetry, current, and wave data. The calculated bottom shear stresses were compared to estimated critical shear stresses for erosion of both natural sediment and dredged material. Spatial distributions of the time-varying ratio of bottom shear stress to critical shear stress were plotted and used to identify areas of relatively higher in situ bottom sediment stability. The calculations successfully identified areas of the mid- and outer continental shelf that had been chosen as good candidate areas in earlier, more-detailed studies. The method is