The Sediment Computation Time Multiplier allows users to decouple the time step for unsteady hydraulics and sediment transport. For stability, the unsteady hydraulic computations in HEC-RAS often require smaller time steps than the sediment model requires. But the sediment computations are a significant portion of the run time.

This method allows users to run sediment computations at some multiple of the hydraulic time step. For example, if the hydraulic model is stable at 6 seconds, and this multiplier is set to 10, HEC-RAS would compute sediment transport with a 1 minute computation increment.

Modelers can use this feature in conjunction with the Unsteady Hydraulics Advanced Time Step Control to optimize the stability-run time trade off.