For Thursday, March 3rd's lab, we will use HEC-GeoRAS to create the geometry data for a HEC-RAS simulation and then use HEC-GeoRAS to derive an inundation map of the output results in ArcGIS. We will use a tutorial that Noah Finnegan (UC Santa Cruz) put together for the NSF-sponsored New Tools in Process-Based Analysis of Lidar Topographic Data.

This zip filecontains all the GIS data, a tutorial document and excel flow data you need to complete the excercise. Warning, since this lab relies on HEC-GeoRAS, you must work on a machine with ArcGIS 9.3.X installed (no HEC-GeoRAS plugin is available yet for ArcGIS 10). The HEC-RAS portion of the lab can be done on any machine with HEC-RAS 4.1.

The LiDaR comes from a location on the South Fork Eel River in Northern California (see Google Map below for interactive context). You may find yourselves in situations where you have very little good information on the hydraulic boundary conditions you would need to run a HEC-RAS model, and no on the ground topographic data for the long profile and cross sections that HEC-RAS requires as geometric data. If you happen to have airborne LiDaR of the site (a scenario becoming more and more common), you may be able to at least build a rough hydraulic model with HEC-RAS using geometry data derived from the airborne LiDaR and some reasonable assumptions about the hydraulic boundary conditions.  The geometric data will be limited by the fact that traditional NIR wavelength LiDaR does not penetrate the water surface and your DEM will likely not show bathymetry. However, LiDaR is often flown at low flows and the geometry data may be good enough for simulating high flows roughly.  Noah's Tutorial walks you through this scenario and in the process will teach you how to use HEC-Geo-RAS.