A numerical model is developed for the simulation of sediment suspension caused by ship navigation in waterways. Erosion and sediment suspension represent an important issue in marine transportation. This is mainly due to increased traffic of the new generation of deep draft ships and the associated tight under keel clearances in shallow parts of seaways and waterways. The sediment suspension model is based on the exact and numerical solution of the governing convection-diffusion equation (CDE). The exact solution is derived for the case of constant coefficients of the CDE using symbolic computation with Maple. When the coefficients of the CDE are a function of the dependent variable, the CDE is nonlinear and its numerical solution is computed using the method of lines. The model computes the vertical profile of suspended sediment in the waterway and accounts for sediment settling and deposition plus erosion from the riverbed and upward diffusion by short period waves and/or a superposed current. The results of the model can be used by engineers and scientists for the assessment of the environmental impact induced by increased ship traffic in the waterway as well as for the identification of potential riverbed areas that are sensitive to sediment resuspension and subsequent erosion.