Combining Runoff in Watershed Basins with WMS

The Watershed Modelling System (WMS) includes use of the Rational Method, which enables the calculation of peak flows for small watersheds in urban and rural areas. This feature can combine runoff from multiple basins to find the values.

The Rational Method requires a couple specific components to calculate the runoff coefficient for an area. The required inputs are soil data, along with either a table relating soil IDs to runoff coefficients, or a runoff coefficient coverage. Composite runoff coefficients use an area-weighted average of all runoff coefficients that overlay each basin for computation. The inputs chosen will depend on what method you choose to calculate runoff in the Rational Method module. The two primary methods to calculate runoff are first, to assign coefficients to polygons within a coverage, and second, to import a table with all of the coefficients already assigned to a land or soil use ID.

Example of Land Use in WMS Example of Soil Group in WMS

There are two ways to assign runoff coefficients to a polygon. The first way is to enter the coefficients polygon by polygon, and the second is to assign the coefficients through the Soil type mapping dialog.

To assign runoff coefficients polygon by polygon, do the following:

  1. Start with a Runoff Coefficient coverage.
  2. Select one of the polygons that intersects the drainage basin.
  3. Enter the runoff coefficient that matches the soil or land type for that polygon in the Runoff Coefficient dialog window that appears.
  4. After entering the data for each polygon that intersects the basin, activate the Hydrologic Modeling Module and go to Calculators | Compute GIS Attributes.
  5. In the Compute GIS Attributes dialog, make sure the following options are active:
    • “WMS Coverages” is selected as the data type.
    • Under Computation, Runoff coefficients is selected on the dropdown menu.
    • The “Use” dropdown is set to runoff coefficient coverage.
    • The “coverage name” dropdown is set to your new coverage.

To assign runoff coefficients to polygons by soil mapping, do the following:

  1. Start with a “Soil Type” coverage.
  2. Select one of the polygons that intersects the drainage basin.
  3. On the bottom left of the Soil type mapping dialog that appears, turn off the "SCS Soil Type" checkbox and turn on the "Runoff Coefficient" checkbox.
  4. You will now have a list of soil IDs and names with a field for runoff coefficients. Enter a coefficient value for each of these fields according to the material type.
  5. Open the Compute GIS Attributes dialog as described above.
  6. Set everything the same as are in the last set of steps, except change the "Use" dropdown to Coverage.

There are multiple ways to create runoff coefficient tables to import into a project. One of the ways is to create a table from scratch. If you choose this route, you can view the structure requirements on the Aquaveo wiki to make sure it includes everything you need. To import a table with the runoff coefficients, do the following:

  1. With the “Soil Type” coverage active, double-click on a polygon that intersects the drainage basin.
  2. Select “Import file” under Import soil attribute file.

You can also import a table in the Compute GIS Attributes dialog.

Head over to WMS and try out the different ways to assign runoff coefficients to your watershed project today!

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Filling Missing Raster Data

Do you have a raster that has holes in it? The Fill Nodata can fix small holes in raster data. Available in GMS, SMS, and WMS. In this article, we will explore the ways that the Fill Nodata tool can be used in WMS.

The Fill Nodata tool fills in small areas or gaps in a raster where no elevation data exists. It is located in the Rasters/Fill Nodata section of the Toolbox. The tool will interpolate an elevation to raster cells that are classified as "NODATA". Then the tool will create a new raster in the project that has the fillable no data areas filled.

Example of the File Nodata tool

These holes in the raster can occur for a number of reasons, one of the most common being that the data is incomplete. WMS is flexible enough that it can use a raster with small amounts of missing data for most simulations. However, it is recommended that you have data that is as complete as possible to ensure the generated model is as accurate. Therefore using the Fill Nodata tool can help ensure the accuracy of your model.

The Fill Nodata tool has a few input parameters to keep in mind. The input raster is the most important parameter. This needs to be a raster that has been imported into the project. The maximum distance to interpolate determines how far out WMS will look to fill data. It will use pixel units to do this. The number of 3x3 average filter smoothing iterations to run determines how many smoothing interactions will be run after the interpolation has been calculated. Additional interactions can help in improving the fill data.

Keep in mind that the tool was not intended to create data for large regions of missing data cells, especially regions on the border of the raster. If you have a large area of missing data, it would be best to use other processes to fill in the missing data, such as downloading the missing data and merging it with your raster.

The Fill Nodata tool is one of thetools provided in WMS to let you modify and edit raster data. Try out the Fill Nodata tool in WMS today!

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Using CAD Data to Delineate a Watershed

Did you know that you can use CAD files to delineate your watershed area in a Watershed Modeling System (WMS) project? WMS is capable of using CAD data for elevation data, designs, layouts, and more. CAD data can be converted to TINs and feature objects to be implemented in a WMS project.

When converting the CAD data to feature objects, you can choose which layers from the data you would like to use when creating the new feature object. After that, you can clean up the feature object and choose all the properties for the coverage. To convert CAD data into feature objects, do the following:

  1. Import the CAD data into WMS from a DWG, DXF, or DGN file.
  2. After importing the CAD data, review the data to verify that it was imported correctly and that it has the correct projection.
  3. Right-click on the file in the Project Explorer and select Convert | Feature Objects….
  4. In the Cad → Feature Objects dialog, select which layers to convert into feature objects.
  5. Make certain the new coverage is set to have the "drainage" type.
  6. Designate the converted feature objects as outlet points and streams. Also verify that any stream arcs a set with the correct direction.

With the CAD data converted to feature objects and you've designated your outlets and streams, you can start the process of delineating your watershed. To do this, you will need a DEM in your project. If you have elevation data stored in a CAD file, you will first need to convert the CAD data to a TIN.

Basin delineated from CAD data

CAD data can be converted into TIN points or TIN triangles, but the best way to end up with TIN triangles is to convert into TIN points first. To convert CAD data directly into TINs, do the following:

  1. Import the CAD data into WMS in the form of a DWG, DXF, or DGN file.
  2. Right-click on the file in the Project Explorer and select Convert | CAD Points → TIN Points.
  3. In the Cad → TIN dialog, select which layers to convert and the name the TIN data will appear under in the Project Explorer.
  4. Right-click on the TIN point data in the Project Explorer and select Triangles | Triangulate.

From here you can convert the TIN to DEM if necessary. The TIN module in WMS has a few tools for working with basins that may be sufficient for your model. However, some models either perform better or require a DEM. Once you have the DEM you can generate the delineated basin. To do this:

  1. Right-click on the TIN and select Convert | TIN → DEM.
  2. Enter parameters for the DEM in the Convert TIN to DEM dialog.
  3. Review the generated DEM.

Once you have a DEM, complete the following steps:

  1. Select DEM | Compute Flow Direction in the Drainage module.
  2. Select DEM | Polygon Basin IDs →> DEM in the Drainage module.
  3. Select DEM | Compute Basin Data in the Drainage module.

Once you have a delineated basin, you can use the basin with the watershed modeling model of your choice. Be certain to review the basin to make certain it contains all of the area you need for your project.

Head over to WMS and see how you can utilize CAD data to create delineated basins in your projects today!

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Announcing WMS 11.2 Beta

Aquaveo is excited to announce the release of WMS 11.2 in beta! WMS continues to provide an all-in-one watershed modeling solution. With the release fo the WMS 11.2 beta, we want to highlight some of the new features you can find in WMS 11.2 beta.

WinTR-20 Model

WMS 11.2 has improved the use of the TR-20 model by incorporating the WinTR-20 numeric model. WinTR-20 uses the same interface as TR-20. WinTR-20 contains upgrades to the source code with some changes to the input and output files. These changes have now been incorporated into WMS 11.2 to let you take full advantage of these features.

Export MP4 Files

MP4 files are now the default when exporting animations. You can export the MP4 files directly from the film loop wizard in WMS. MP4 files make sharing animations you’ve created in WMS easier.

The Toolbox in WMS 11.2

WMS 11.2 introduces the Toolbox which contains many tools for manipulating data and geometries. This is reached through the Toolbox macro. Of particular use for WMS projects are the tools related to working with rasters and lidar data allowing to trim, merge, and smooth this data along with many other options. The toolbox also contains many tools for working with coverages and datasets.

Color Ramp Options

The final new feature is the changes to the color ramp options. The color ramp now contains multiple preloaded color palettes. Options have been added to reverse pallets and to save your favorite palettes for easy access in the future. The preloaded palettes can also be duplicated and customized to meet your project's needs.

These are a few of the new features that come out with the release of WMS 11.2. Try out these features and more by downloading WMS 11.2 from the Aquaveo website today!

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