Variable Time Steps and Time Slicing in HEC-RAS

It is often (very often) useful to subdivide time steps in time or space, using smaller time steps to resolve critical conditions in your unsteady 1D and/or 2D model. You will often need a small time step during large flows or in small cells, but don't want to use that time step for all time/space.

There are two common approaches for subdividing time steps: adjustable time steps and time slicing. The former subdivides time steps temporally, in response to they critical courant condition, the latter subdivides time steps spatially, applying different time steps to meshes with different resolutions. Both are really valuable, and this video helps make sense of when to use which...and how.