HEC-RAS can plot and animate cross section changes computed as part of a sediment run. Cross section data is usually much more memory intensive since the vertical position of each node on each cross section is stored. Therefore, cross section output is turned off by default and must be selected by checking the Cross Section Bed Change Output check box. When users select cross section output the multiple that controls cross section output is multiples of the profile output. For example, in the figure in Output Level,  output is generated every 10th profile output or every 100th computation increment. To set the cross section output to write for every profile set the Number of Profiles Outputs Between XS Outputs to 1.

As a default HEC-RAS reports variables after every tenth computational increment and at the end of each flow duration. Choosing a less frequent output interval yields a minor improvement in run times.

Modeling Note – Large Output Files:

Choosing a high Output Level (e.g. 6) and a low time increment between outputs (e.g. 1) can produce extremely large sediment output files. The classical viewers have a 2GB limit. If output files grow larger than that limit, they will not open, and large files under that limit can be very sluggish. The new HDF5 sediment output viewer can open much larger files, working well with multi-GB files. However, small time steps and large variable requests can produce very large (e.g. a 20 year unsteady sediment model run at a 5 min time step can produce a 30GB output file) which can impact performance.