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, brings the power of HEC-GeoRAS into the free/libre software world.

Homepage: http://rivergis.com