I have cross sections that I created in hec-georas using a 20m resolution DEM (which i had converted in TIN before extracing elevations along the cross section).When i used the RASMapper and associated the terrain to the geometry in HECRAS 5.0.1, it showed a well defined terrain that was not visible in arcgis. The cross sections were flat and it completely different from the underlying terrain. I’d like to know what is it that HEC-RAS does to the TIN that ArcGIS fails to do.