HEC-RAS limits cross sections to 500 station-elevation points. But 500 points is almost always far more than required to adequately represent the shape of the cross section. In hydraulic modeling, too many station-elevation points can affect run time (which is exacerbated in sediment which runs the steady flow computations every time step) but is mostly innocuous. Dense station-elevation points can cause several issues in a 1D sediment transport model including bed inversion and node stranding.
Almost any cross section can be reasonably represented with 100 station-elevation curves and sediment models often perform best when cross sections are limited to 60 station-elevation points or less. To optimize the shape representation with the fewest station elevation points use the point filter in HEC-RAS. In the geometry file, select Tools--> Cross Section Point Filter. See the main HEC-RAS user manual to learn about the different options and how to evaluate the quality of the filter methods, but the simplest method to reduce the cross section point density is to select the Multiple Location and Minimize Area Change tables (below), and define the maximum station-elevation points. Then press the button to select all cross sections. Press the Filter Points on Selected XS button to filter.
After you filter the cross sections, you can return to the Single Location tab and evaluate the filter, making sure it retains the shape of the cross section, and press Restore XS if it went poorly.
