RiverGIS is a QGIS plugin that helps you create HEC-RAS flow model. HEC has developed an excellent tool for that, the HEC-GeoRAS for ArcGIS. While HEC-GeoRAS can be downloaded and run at no cost, the ArcGIS licence can drain your pocket heavily. RiverGIS, released under the [GNU General Public License](<http://www.gnu.org/copyleft/gpl.html), brings the power of HEC-GeoRAS into the free/libre software world.
Homepage: http://rivergis.com