This study investigates flow and sediment transport patterns within the lower reaches of the Athabasca River (~200 km) in Alberta, Canada. These reaches are characterized by complex bathymetry, regions of high tortuosity, and variable discharges and bed slopes. Sediment within this reach is primarily sand and gravel, but there is also a high percentage (>10%) of cohesive sediment with unique settling properties. A regional Environmental Fluids Dynamics Code (EFDC) 2D numerical model was setup to predict hydrodynamics of the flow and suspended sediment transport. Bathymetry measurements were obtained from a combination of high resolution 3D Geoswath and ADCP surveys, and detailed 2D cross-section measurements. A local high resolution 2D numerical simulation was also completed for a reach near Steepbank River (<20 km) to better understand the effects of a coarser grid resolution on the regional model predictions. Model results were validated using field measurements including water surface elevations collected with Global Positioning System (GPS), water velocities collected using a Gurley current meter, and suspended sediment measurements obtained from the Regional Aquatics Monitoring Program. The results showed that the regional model was capable of making reasonable predictions of water surface elevations, flow velocities, and suspended sediment concentrations. Simulation results with a rigid bed, estimated sediment inputs and assumed parameters, have also shown that a large proportion of incoming sediments get deposited along the lower reaches of the Athabasca River, and the model was able to identify those major depositional areas.