Modeling short-term behavior of dredged material disposed in very shallow and very deep coastal waters

Modifications have been made to the model for Disposal From an Instantaneous Dump (DIFID), commonly used to simulate transport and fate of dredged material rapidly disposed from a dredge or barge into aquatic systems. Changes include simulation of particulate and contaminant detachment from the descending cloud into the water column, and detailed representation and simulation of discharge dynamics. The latter include effects of vertical density gradients within the dredge hopper on discharge rates, dynamic simulation of exit speed and mass discharge rate from the hopper, and representation of the release as a line source. These revisions increase the range of physical processes incorporated in the model, permit more realistic calculation of particulate and contaminant concentrations in the water column, and extend its applicability to a broader range of depths. The model gives reasonable agreement with water column and benthic results obtained in a field study of disposal into a 12-meter water column. Data for model calibration and verification in deep water are not available at this time.