HEC-RAS routes sediment with the Exner equation, modeling sediment mass with the continuity equation. This approach includes no physical limitation on sediment velocity and, depending on cross section spacing and time step, often moves sediment faster than the water velocity.
HEC-RAS includes an option that limits sediment velocity to the water velocity, only releasing sediment from each control volume that the water passing through that control volume can carry. To activate this option, select Sediment Routing Method from the Options menu and pick Limit to Water Velocity from the drop down list.
Wish List: 1D Advection-Diffusion
We would like to improve on this simplification, offering the Advection-Diffusion equation to route sediment according to more physical processes and user specified coefficients.
