#Hec ras blogspot how to#
Either way, approaching anunsteady HEC-RAS model (especially a dynamic one) as a beginner with little experience andunderstanding of how to stabilize it can cause significant delays in your project and worse,completely blow up your budget. Sometimes you canget your simulation to complete without crashing, but the listed numerical errors are so high that youcant with good conscience submit that as your final simulation. Then youve painstakingly spent hourspossibly days entered all of that data only tofind that once you press the Compute button, the model crashes. You know, youve gone to great lengths collecting the best survey/topo data and solidhydrology. Stabilizing a Dynamic Unsteady HEC-RAS Model Written by Chris Goodell | WEST ConsultantsOne of the most frustrating aspects of unsteady HEC-RAS modeling can be the model stabilizationprocess. , GIS, HEC-RAS, Lateral Structures, Station-Elevation Points, Storage Areas Voila! Hope you liked this new (for me) discovery.Įmail ThisBlogThis !Share to TwitterShare to Facebook Labels: Connection, Filter, GeoRAS. HEC-RAS will still give you an error if you try to run the model with this data (the limit of 500 pointsstill stands for computations!), but a simple click of the Filter button you s ee in the figure abovesolves the problem. It turns out that RAS automatically expands its Station Elev ation table to store however manypoints you need. For example, inthe connection called 83Coal in the figure above, I end up with over 2300 points. The bad part about that is that extracting tools in ArcGISdoesnt really have an option to limit the number of points that are generated, and you end up withthousands of points that you cant really use in HEC -RAS (the limit for cross section points, storagearea connection weir/embankment points, and lateral structure weir points is 500). The shortcut is tothink outside GeoRAS and obtain simple 3D station-elevation points directly from a TIN or grid forthe storage area or structures you need. Itis especi ally difficult if youre not the one who built the model in the first place. HEC-GeoRAS seems to have some issues exporting data when you take anexisting project and try to modify shapefiles and extract data for only a portion of the entire model. Now we need station-elevation data for storage area connections and lateral structures. The new reach (now a storage area) will look like theone below. In order to do that, we need to delineate the storage area polygon, define new storage areaconnections, and generate lateral structures. We happen to have the topographic data used to generate theoriginal model (although we dont have the original geodatabase), so were good to go. For example, I want to convert the reach below(from 5.43 to 0.55) to a storage area. In the process, Im converting a few tributaries into storage areas(which are surrounded by other storage areas). I am working on a dam breach project where Im trying to simplify a complicated model with dozensof tributaries and storage areas.