Geospatial Hydrologic Modeling Extension HEC-GeoHMS, User’s Manual. Public Domain That information is also provided in Appendix E of this manual for. This tutorial is designed to expose you to basic functions in HEC-GeoHMS ( ArcGIS version) to create input files for hydrologic modeling with HEC-HMS. Step 7: Terrain processing and HEC-GeoHMS model development The DEM, land use and soil data used in this tutorial are already clipped.
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Double click at this point to finish digitizing the Tule Tributary. You will get a summary of number of points removed for the filtered cross-sections. The cell size of dtmgrid is equal to the Rasterization Cell Size you chose in the layer setup window. Confirm the input datasets to be checked, and click OK. Map to HMS Units. Select the options shown above. This function allows preparing subbasin and river features for export.
Step by Step: Flood Hazard Mapping
Flow Direction Grid This function computes the flow direction for a given grid. Another annoying fact is that GRASS uses proprietary raster and vector layer formats but those can be fairly easily exported to Shapefile or other spatial data types. This function computes the flow direction for a given grid.
The values in the cells of the flow direction grid indicate the direction of the steepest descent from that cell. You will notice that only a few cross-sections had points removal. Prepare Data for Model Export. Flood Hazard Mapping Overview. To create the channel centerline in Banks feature classstart editing, and choose Create New Feature as the Task, and Banks as the Target as shown below: DEM Reconditioning The function needs as input a raw DEM and a linear feature class like the river network that both have to be present in the map document.
The flowpath layer contains three types of lines: Sometimes you will realize at the end! The area with positive results meaning water surface is higher than the terrain is flood area, and the area with negative results is dry. To define downstream boundary, click on Reach Boundary Conditions. The resulting attribute table should look like below: ArcGIS uses an old algorytm that my be failing under certain conditions. Fill Sinks This function fills the sinks in a grid. For this tutorial we will run the model in steady state condition.
Eventually, we are going to use these land use classes and soil group type, in conjunction with runoff curve numbers CNto create the curve number grid.
This process takes a few minutes. Before creating an import file, make sure we are exporting the right layers. The River and Reach attributes contain unique names for rivers and reaches, respectively.
Additional datasets that may be useful are aerial photograph s and land use information. Even if we yutorial not create a gage file, there will be a gage file created when the met model file is created. You can specify the methods that HMS should use for transform rainfall to runoff and routing channel routing using this function.
HEC-GeoRAS Export Error | GeoNet
This function populates the BasinLag field in the subbasin feature class with numbers that represent basin lag time in hours.
The output is the Catchment Grid layer.
You should now see the Arc Hydro toolbar added to ArcMap. Interactive Point Delineation An alternative to delineate watersheds when you do not want to use the batch mode process a group of points simultaneously to generate the watershed for a single point of interest is the Point Delineation tool. Subwatersheds delineated from a set of points are therefore by definition non overlapping because the watershed draining to a point that is within another watershed is excluded from the subwatershed of the downstream point.
Creating bank lines is similar to creating the channel centerline, but there are no specific guidelines with regard to line orientation and connectivity – they can be digitized either along the flow direction or against the flow direction, or may be continuous or broken. Finally, digitize the lower Baxter reach from junction with the Tule Tributary to the most downstream end of the Baxter River.
Help inserting CN Grid in HEC-GeoHMS | GeoNet
Creating Bridges and Culverts After creating cross-sections, the next step is to define bridges, culverts and other structure along the river. Can anybody imagine, where the error in the procedure is? Each line in the feature class carries the identifier of the catchment in which it resides. Take a closer look at the DEM and use your judgement to determine if the DEM is truly representative of actual conditions. The TIN tP that is created in this step will define a zone that will connect the outer points of the bounding polygon, which means the TIN will include area outside the possible inundation.
Catchment Grid file name: WatershedPoint and Watershed are default names that can be overwritten. If you face problems in creating Project Area, just delineate a watershed using the point delineation tool in Arc Hydro for the Project Point feature, and load this watershed polygon into ProjectArea feature class. For example, each river has a station number of zero at the downstream end, and is equal to the length of the river at the upstream end.
We will use this to locate the outlet of the watershed. If you click at a point along the profile, a corresponding point showing its location on the river reach will be added to the map display shown below as red dot.