Data Files

You will be working with a section of the White River at Muncie, IN.   The data for this tutorial are provided in the zip file.

Meteorological Data.zip

Objective

This workshop will help students learn how to specify meteorological data including precipitation, evapotranspiration, and wind. In addition, the workshop also includes how to setup infiltration. This work has been tested with HEC-RAS Version 6.7 beta 5. However, the same steps should work for Versions 6.0 to 6.6.

Base Plan

The terrain data (and a depth map) that was used in the HEC-RAS model for Bald Eagle Creek is show below. Evaluate the existing plan.

  1. Open HEC-RAS and the “BaldEagleDamBrk.prj”
  2. Run the “Single 2D Area”
  3. Animate the results in RAS Mapper.

Note the model setup including the geometry, dam, computational options and tolerances, and boundary conditions. Note where water is spilling into the town. The base plan is setup as a single 2D area with the dam modeled as an SA/2D Connection. The reservoir has a single inflow hydrograph. The dam as a Time-Series Controlled Gate Openings. The downstream boundary is a Normal Depth boundary condition.

Gridded Precipitation

This task will add gridded precipitation to the base model plan. The gridded precipitation DSS file has already been created.

  1. Create a new Unsteady Flow Data file and call it “Gridded Precip”.
  2. Within the Meteorological Data tab of the Unsteady Flow Data editor, click on the drop-down menu next to Precipitation/Evapotranspiration and select Enable.

    The Precipitation and Evapotranspiration fields will be enabled under Meterological Variables.

  3. In the section called Precipitation, select Gridded in the Mode drop-down menu as shown below.
  4. Make sure the Source drop-down menu is set to DSS.
  5. In the section DSS Data click on the open icon and select the DSS file called “precip.2018.09.dss” located in the Precipitation folder of the project folder. The HEC-RAS DSS Viewer will open. Set the DSS path parts as shown in the figure Then double-click on any of the rows to set the path and click on the OK button.

    The Unsteady Flow Data editor should look something like the figure below.

  6. Save and close the Unsteady Flow Data
  7. Create a new plan called “Gridded Precip” with the new unsteady flow data and run it.
  8. Before inspecting the results, inspect the gridded precipitation in RAS Mapper. Open RAS Mapper and select the Gridded Precip layer under the Event Conditions For the precipitation to display properly it will be necessary to adjust the surface colormap. Animate the precipitation. The gridded precipitation should look something like the figure below.
  9. Inspect the HEC-RAS results and compare to the plans with and without precipitation. Use a different colormap for the water surface elevations highlight the differences or compare the extents of the water surface and velocity layers. See the example below.
  10. Add the Cumulative Precipitation Depth result in RAS Mapper by right-clicking on the “Gridded Precip” plan and selecting Create a New Results Map Layer… from the menu. In the Results Map Parameters editor, select Cumulative Precipitation Depth under the Additional 2D Variables layer, click on Add Map, and Close the editor.
  11. Adjust the colormap and inspect the spatial distribution of the precipitation.
  12. Compare the results with and without precipitation by plotting time-series and spatial maps in RAS Mapper.

Infiltration

The SCS Curve Number method can be parameterized using a combination of both Land Cover and Hydrologic Soils data or only one of those datasets. In this workshop both the Land Cover and Hydrologic Soils data are utilized. First, a Soils Layer is created based on the USDA gSSURGO database (https://www.nrcs.usda.gov/resources/data-and-reports/gridded-soil-survey-geographic-gssurgo-database). Then, an SCS Curve Number Infiltration Layer is created based on both the Soils Layer and the Land Cover classification layers.

Soils Layer

This section covers how to create or load an existing Soils Layer in RAS Mapper.

  1. Create a Soils Layer by right-clicking on Map Layers and selecting Create a New RAS Layer.
  2. In the Browse for Land Classification Files window, select the GSSURGO folder called gSSURGO_PA.gdb in the Soils Data folder in the main project directory.
  3. In the Create a New Soils Layer editor, click on the add button as shown in the figure below and select the file in the Soils Data folder in the main project directory.
  4. Replace “/” with “-“ and “(none)” with “NoData” in the Classifications to dashes as shown in the figure below.
  5. Click on the Open Folder icon and save the Filename as “Soils.hdf” in the Soils Data folder in the main project
  6. In the Create a New Soils Layer window shown above, click Create and then Close in the Compute Window
     
  7. To demonstrate how to load an existing Soils Layer and to prevent any issues with the previously created Soils Layer, an existing Soils Layer is loaded and used in the workshop. First remove the Soils layer from RAS Mapper. To add an existing Soils Layer open RAS Mapper, right-click on the Map Layers, and select Add Existing RAS Layer | RAS Classification Layer as shown in the figure below.
  8. Select the Soils Data layer called “Hydrologic Soil Groups.hdf” in the folder called “Soils Data” in the BaldEagleCreek folder as shown below and select Open.
  9. Inspect the Soils Layer in RAS Mapper. The layer should look something like the figure below

Infiltration Layer

This section describes how to create or add an existing infiltration layer. In order to avoid any issues with the created infiltration layer, the workshop will continue with a previously created infiltration layer.

  1. Create an Infiltration Layer by right-clicking on the Map Layer and selecting Create a New RAS Layer | Infiltration Layer From Land Cover / Soils Layers as shown in the figure below.
  2. In the Infiltration Layer window, set the options as shown in the figure below and click Create. As mentioned previously, it is not necessary to utility both the Land Cover and Soils Layers for the SCS Curve Number method, but more accurate to do so.
  3. Inspect the Infiltration Layer in RAS The layer should look something like the figure below.
  4. Right-click on the SCS Curve Number Infiltration Layer and select Edit Infiltration Data Table.
  5. The Classification Parameters window will appear. The table contains all the land classifications which need to be assigned SCS Curve Number infiltration parameters.
  6. For the purposes of the workshop, an Excel spreadsheet has been provided with the SCS Curve Number parameters. Open the spreadsheet called “Curve Number.xlsx” located in the Infiltration folder of the main project directory and copy the values to the Classification Parameters Then Click OK to accept the values in the table.
  7. To demonstrate how to load an existing Infiltration Layer and to prevent any issues with the previously created Infiltration Layer, an existing Infiltration Layer is loaded and used in the workshop. First, open RAS Mapper and remove the previously created Infiltration Layer. Then right-click on the Map layer and select Add Existing RAS Layer | RAS Classification Layer. Select the Infiltration Layer called “Curve Number” located in the folder “Infiltration” folder and select Open.
  8. To utilize the infiltration parameters, the Infiltration Layer needs to be “associated” with a geometry. Preserve the existing geometry without infiltration calculation, and create a new one by right-clicking on the geometry and selecting Save Geometry As…

  9. In the Save Data As window, save the new Geometry as “Single 2D Area – Curve Number”.
  10. Right-click on the root Geometry node in RAS Mapper and select Manage Geometry Associations or go click on the menu Project | Manage Layer Associations… as shown below.
  11. Set the Infiltration layer to Curve Number for the corresponding Geometry as shown in the figure below.

  12. Set the % Impervious Layer to Land Cover for the corresponding Geometry as shown in the figure below and click Close.
  13. Right-click on the Land Cover layer and select Edit Land Cover Data Table.

  14. The % Impervious values have already been Inspect the values.

    Open Water is considered to be 100% impervious for hydrologic and hydraulic modeling because it has no infiltration capacity. Similar to impervious surfaces, any precipitation on an open water body will contribute 100% to the runoff.

  15. Inspect the Land Cover layer by setting the opacity/transparency to 50% and overlaying the layer the Do this by right-clicking on the layer and selecting Layer Properties. Then close the Layer Properties window.
  16. Find areas in the channels that do not correspond to Open Water (see examples in figure below).
  17. Practice fixing areas like this using Classification Polygons. Right-click on Classification Polygons and select Edit Layer. Then click on the Add New Feature tool .
  18. Draw polygons over the areas which need to After each polygon is drawn, an editor will appear to select the Classification for each polygon. Select the Main Channel classification and clock OK.

  19. After creating a few polygons, right-click again on the Classification Polygons layer, and select Stop Editing.
  20. The window below will Click on Yes to save the edits.
  21. Create a new plan called “Gridded Precip CN” with the new Geometry called “Single 2D Area – Curve Number” and run it.
  22. Inspect the results and compare to the previous plans using profile and time- series plots in RAS Mapper.

Evaluating the time series near the downstream end of the model, you can see that some of the largest differences occurred during the middle of the simulation. This happens to be when a significant amount of rainfall fell on the watershed. The base model does not include precipitation which is why it doesn't include the additional peak. The "Gridded Precip" scenario has the highest water level followed by the "Gridded Precip CN" scenario. The "Gridded Precip"  scenario includes the additional flow from the precipitation but does not account for infiltration losses like that of the "Gridded Precip CN" scenario. The largest differences in inundation are in the Lock Haven area and the downstream area. Around Lock Haven, the levees did not overtop for base scenario that only includes inflow hydrographs. However, for the gridded precip events, Lock Haven received rainfall within the leveed area and the rain eventually pooled in the lower portions of the protected area. The downstream saw larger inundations due to the increase in flow from the addition of the precipitation which resulted in more flow accumulated along the reach.



The channels are listed as open water in the land cover data. The open water used a 100% impervious rate which assumes no infiltration.

 

For this analysis, the SCS Initial Reset Time (hrs) was set to 24 hours under the classification parameters in the Infiltration Layer file. The infiltration layer was reset after 24 hours of no precipitation. 

Potential Evapotranspiration

In this section, a time-series of potential evapotranspiration is added. The time- series is specified at a single meteorological station.

  1. Create a new Unsteady Flow Data file called “Gridded Precip Evap”.
  2. Next, create a Meteorological Station, by clicking on the button labeled Create/Edit Stations...

  3. In the Meteorological Stations editor, click on the new button, call it Sayers Dam, and enter either the WGS84 or projected coordinates shown below.
  4. Click on the Plot Stations
     

  5. In the Evapotranspiration section, set the Mode is set to Point, and click on the button to expand the section as shown below.
  6. Click on the Edit button shown
  7. In the Meteorological Point Location Time Series window, enter the hourly potential evapotranspiration data for Sayers Dam as shown in the figure below. The data has been provided in an Excel spreadsheet called “PET.xlsx” located in the Potential Evapotranspiration folder of the main project directory. Once all the data is entered click on the OK
     
  8. Open the Unsteady Flow Analysis editor and create a new Plan called “Gridded Precip CN Evap”.
  9. Save the plan and run
  10. Compare the results with the previous plans in RAS Mapper. Specifically, plot the Cumulative Evapotranspiration Depth at various points.

As expected, the plan with the evapotranspiration produced lower wsel across the model due to the additional losses from the evapotranspiration.