In this study, SEDDEER ( Sed iment De position and Er osion), a stand-alone sediment and contaminant model which simulates one water box and the underlying multiple sediment bed layers, was incorporated into Water Quality Analysis Simulation Program (WASP7.4). WASP7.4 toxic module (TOXI7) was modified to include SEDDEER to develop WASP_SEDDEER model. Tests were designed to ensure that the coupling of the WASP7.4 and SEDDEER bed models is correct. The tests compared WASP_SEDDEER one-box simulations against SEDDEER results to verify fluxes across the sediment-water interface. Also, two-vertical-boxes water-column model tests were performed to compare WASP_SEDDEER output against Environmental Fluid Dynamic Code (EFDC) solutions. The comparisons revealed a good fitting between WASP_SEDDEER and EFDC results (R² values above 0.95) verifying a successful incorporation. Exploratory applications of EFDC, WASP7.4, and WASP_SEDDEER to Mobile Bay for simulating sediment and contaminant transport showed the capabilities of WASP_SEDDEER for estimating suspended sediment and contaminant concentrations throughout the computational domain.