I'm a novice with HEC-RAS. I'm getting the above warning for certain cross sections in my model. When I view the cross sections using the animate option, the highest water level is >100 m below the top of the cross section. Increasing the number of cross sections with "XS interpolation" does not help. Neither does increasing the height of the valley walls. Someone suggested modifying HTab, but I could not see where in HTab to do this. Any help would be appreciated.
Interpolating XS isn't going to help as that is not the problem.
You need to increase the Htab limits. In the geometry editor on the left side there is a button called HTab Param. If you haven't opened this before it will be set to what RAS thought would work. First thing is to highlight the starting el column and then hit the "copy invert" so that the Htab start at the channel flowline. If using v4.1 you have a maximum of 100 points so set it at 100 and then adjust the increment so you are above a few feet (or a meter) above the WSE. If v5.0.1 you have more points so have more flexibility. I typically stay around 100 points and increments of .25'+/-.