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George Mason University Department of Civil, Environmental and Infrastructure Engineering

Dr. Celso Ferreira

Exercise Topic: HEC – GeoRAS Post-Processing

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Objectives: This tutorial is designed to walk you through the process of creating flood maps products from a HEC-RAS simulation

including extracting flood delineation polygons, water depths and velocity rasters. It also includes running a simple steady flow

simulation with HEC-RAS from a previously created HEC-GeoRAS set-up.

**Refer to the HEC-GeoRAS User Manual for definitions and context of the steps and tools in this tutorial, found in the Help Menu of the GeoRAS toolbar.**

Tutorial DEM obtained from GMU Campus Lidar file (provided)

Versions used for this tutorial: HEC-GeoRAS 10.1, ArcMap 10.2.2 (Student), ArcCatalog 10.2.2, HEC-RAS 4.1.0

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*Continued from Intro GeoRAS Tutorial Modify GIS Data in HEC-RAS

1. Save imported project geometry.

2. Click the icon for “Bridge/Culvert”.

3. Note that the bridge geometry did not import properly (this is common).

4. Click the icon for “Deck/Roadway”.

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5. Enter the distance from the

upstream bridge face to the closest upstream cross section.

6. Enter the bridge width.

7. Enter sample bridge deck geometry data.

8. Click “OK”.

*Refer to the HEC-RAS tutorial for details on each field.

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Ensure

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Enter Flow Data and Boundary Conditions

1. Select the “Steady Flow” icon from the main window toolbar.

2. Enter sample flow data for each reach.

3. Click “Reach Boundary Conditions”.

4. Highlight the “Upstream” cell for the first reach.

5. Click “Known W.S.” [water surface].

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6. Enter a sample water surface

elevation.

7. Repeat Steps 4 through 6 for the other two reaches.

8. Click “OK”.

9. Click “Apply Data”.

10. Close the Steady Flow Data window.

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Run HEC-RAS Simulation

1. Select the “Steady Flow Simulation” icon from the main toolbar.

2. Select the geometry and flow data.

3. Confirm that “Subcritical” flow is selected.

4. Click “Compute”.

5. Click “Close” after the successful simulation run.

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6. Click the Geometric Data icon.

7. Select the new Simulation Run

data from the WS Extents drop-down menu.

8. Observe the water boundaries within each reach resulting from the sample flow data.

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Export HEC-RAS Results

1. Select “Export GIS Data” from the main File menu.

2. Confirm that all reaches (3/3) are selected.

3. Confirm that the “Water Surfaces” is checked.

4. Confirm that the new Simulation Run profile data is selected.

5. Confirm that the River Centerlines are selected.

6. Check the box for “User Defined Cross Sections”.

7. Select the desired output parameters (Reach Lengths, Bank Stations, Ineffective Areas, Blocked Obstructions, Manning’s n).

8. Click “Export Data”.

9. Click “OK”.

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ArcGIS – Convert Export to XML

1. Open ArcGIS and enable the HEC-GeoRAS toolbar.

2. On the GeoRAS toolbar, click the “Import RAS SDF File” icon.

3. Select the file that was exported from HEC-RAS.

4. Click “Open”.

5. Click “OK”.

6. Click “OK” upon successful conversion to XML format.

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Setup New Project

1. Select “Layer Setup” from the RAS mapping drop-down menu.

2. Select “New Analysis” and assign a file name.

3. Select the XML file containing the RAS export.

4. Select the radio button for “GRID” and select the original GMU DEM. *The DEM must be saved to the same folder as the exported data (current workspace).

5. Select the folder location of the

current workspace. *Must be folder, not a geodatabase.

6. Click “OK”.

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Populate New Project

1. Select “Import RAS Data” from the RAS Mapping drop-down menu.

2. Confirm that the exported XML file is selected.

3. Click “OK”.

4. Click “OK” upon successful import.

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Create Water Surface Layer

1. Select “Water Surface Generation” from the RAS Mapping > Inundation Mapping drop-down menu.

2. Select the imported Simulation Run profile.

3. Click “OK”.

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Calculate Water Extents

1. Select “Floodplain Delineation Using Rasters” from the RAS Mapping > Inundation Mapping drop-down menu.

2. Select the imported Simulation Run profile.

3. Click “OK”.

4. Click “OK” upon successful mapping.

**Discontinuities in the flow are expected. Only a sample bridge was drawn during this exercise, but all real-life bridges and culverts still exist in the DEM. They have a surface elevation higher than the simplified flow path imported from RAS. As long as the flow volume does not exceed bridge and culvert capacities, there is no impact to the model results shown at right. To be technically correct, or to accurately model extremely high flow volumes, all bridges and culverts should be drawn.