2D sediment transport models in HEC-RAS require four files: an unsteady flow file, a geometry file, a sediment file, and a plan file to tie them together. The sediment data file inherits important information from the geometry and flow data (e.g. Bed Material Classifications and boundary conditions). Therefore, it is important to define sediment data after the geometry and flow data are complete. If the geometry changes, the sediment data may need updates before them model can run.
Additionally, sediment results are very sensitive to hydraulic results. An HEC-RAS sediment model will not be robust or reliable if it is not built on a well constructed hydraulic geometry (USACE, 1993, Thomas and Cheng, 2008). Before adding sediment data, test the hydraulic model over the expected range of flows using the HEC-RAS Unsteady Flow Analysis option, calibrating the bottom roughness and if necessary, the turbulence coefficients. It is recommended to identify hydraulics model problems before adding the bed change complexity. Only add sediment data after crafting a careful, robust, hydraulic model (see section on Hydraulic Best Practices for a 2D Sediment Model).
This section focuses on the sediment data required to build a 2D sediment model. Many of the 2D sediment parameters and data inputs are the same as require for 1Dsediment. To enter sediment data, select Sediment Data from the Edit menu or press the sediment data icon. The sediment data editor (pictured below) has two tabs: Boundary Conditions and 2D Bed Gradations. These tabs are mandatory for 2D simulations. This section also includes important sediment information, data, and parameters that you can define in the Options menu of the Sediment Data editor and the Sediment Options and Tolerances in the Unsteady Analysis window.
Figure. Sediment Data editor.