Aquaveo & Water Resources Engineering News

Do you have raster data that you like to use to quickly generate polygons for your Surface-water Modeling System (SMS) project? SMS 13.3 introduces the Polygons from Raster Bounds, Polygons from Index Raster, and Polygons from Raster Nodata tools Each of these tools make use of raster data to generate polygons in the Map module. This can help you quickly define model domains or areas of interest in your model.

All of these tools can be found under the Coverages section in the Toolbox. Two of these tools can help resolve issues where the raster data is missing data. These "no data" areas can occur when the raster is trimmed, or when some of the data is incomplete in the database of origin.This can create holes in the data that will interfere with a model.

Using the Polygon from Raster Bounds tool creates a polygon that includes only the active region within the raster. It is especially useful when a downloaded raster has been trimmed to the model area. It eliminates the "no data" areas on the edges that were created by the trimming. This cleans up the data for the model. It can also be used when running models, such as for flooding, when one area needs a different coverage than the original.

With Polygons from Raster Nodata tool, areas that are "no data" inside active regions can be separated from the active regions so the "no data" areas don’t interfere with the model. For example, modeling a river, but not the flood plain, means you may want to exclude the land including islands in the river. Using this tool, polygons can be placed around all active areas and defined for the surface water model while the NODATA areas can then be ignored.

The Polygons from Index Raster tool can come in very handy when elevations and materials match fairly well. It will only work if an index raster is being used. Using this tool, polygons can be created around elevation changes in such a way that it becomes much easier to assign materials to polygons.

Creating the polygons can be a time consuming task. These tools can automate part of the process and eliminate some of the problematic areas within your surface modeling area for you. You can use more than one of these tools, as your model requires.

Head over to SMS and try out these tools in the Toolbox today.

The Surface-water Modeling System (SMS)[2] continues to expand the types of data it can use for your water modeling projects. For models in the United States, there is a very comprehensive set of elevation data that you can use in your modeling–3DEP data.

3DEP data is an amalgamation of high-resolution 3D elevation and 3D hydrography data from multiple sources. It is also "bare earth," meaning the images are ground-level only. No buildings, trees, shrubs, or ground cover of any sort have been included. Seeing the most precise shape of the ground can be very important to surface modeling. The high quality lidar data in the 3DEP project covers the vast majority of the United States and several of its territories. Coverage is becoming more comprehensive over time. We have added 3DEP as one of our options when you import map elevation information from the web.

When creating a surface-water model, you are looking for the USGS 3DEP Bare Earth DEM (North America) option from the web.

To access 3DEP data in SMS, do the following:

1. Click File | Import from Web… to open the Virtual Earth Map Location.
2. Make your location selection here (United States and some territories only)
3. You may have to set your Display Projection settings
4. When you reach the Data Service Options dialog box, scroll right until you see an option for USGS 3DEP Bare Earth DEM (North America).
5. You then save your image to the appropriate location on your computer, after you set or accept the default raster cell size.

Once you have saved your image, it will show up in the Project Explorer window under GIS Data. When saving, it will add the " _elevs.tif" extension to the name you chose. The elevation data can then be applied to your model in the usual way.

Head on over to SMS and see how 3DEP data can help your surface-water modeling.

The Ground-water Modeling System (GMS) includes multiple methods of setting the starting heads in the Initial Conditions (IC) package for MODFLOW 6. Starting with GMS 10.8, you can use the top elevation data already entered in the Discretization by Vertices package (DISV) for your starting head values without any extra steps.

When you open the Initial Conditions (IC) dialog, it shows several options for setting the starting heads. For simple models you can set a constant value for starting heads across the entire grid. But for more complex models, you'll want values to better represent the test area. This often means you have to either manually enter, copy and paste, or import from another data file.

However, doing this sometimes involves duplicated work you might have already completed in the DISV package. To eliminate this inefficiency, GMS 10.8 has added a new method that allows you to use the DISV top elevation data as your starting head values. This can be done using the following steps:

1. Open the Initial Conditions (IC) dialog.
2. Check on the box that says "Set starting heads equal to cell top elevations."

Turning on this option will match the starting heads to the elevation data already imported or entered in the DISV package and grays out all other parts of the dialog.

Using this option, the top elevation data will be used as the starting head values during the MODFLOW 6 simulation run. Setting the starting heads equal to the top elevations in GMS offers some benefits:

• It provides an additional option for inputting the starting heads data.
• It can save you time by using data already in the model.

As always, it is best to review the data before running the simulation and after running the simulation to verify that the values were incorporated correctly.

Now head over to GMS 10.8 and check out using your top elevation data as your starting heading values in your MODFLOW 6 projects today!

The Surface-water Modeling System (SMS) provides a useful tool that generates an estimated water surface elevation on an "Exit-H" boundary condition in an SRH-2D model. The Channel Calculator in SMS makes it easier to calculate water surface elevation values. It also gives you greater control of over the parameters

When building an SRH-2D model, the exit boundary will need to be defined. A constant elevation is often used, but this can not be sufficient in many cases. The Exit-H boundary condition is a stage type exit boundary where water surface elevation may be given as a constant number or as a stage-discharge or rating curve. The Channel Calculator is used to compute and assign a normal or critical water surface elevation for the outflow boundary condition. It also gives you greater control over the parameters used to determine the outflow conditions.

The Channel Calculator is accessed through the SRH2D Assign BC dialog. The Populate using Channel Calculator button appears at the bottom of the dialog when "Exit-H (subcritical outflow)" is selected as the BC Type and the Water Surface Elevation option has been determined.

The Channel Calculator specifies a composite roughness value, slope, and flow. SMS extracts a ground elevation cross section from a specified underlying elevation data source (mesh) that is used to compute the area and wetted perimeter. The calculator can make use of different types of elevation data sources which include DEMs, meshes, and scatter sets. Roughness and slope values will be required for the final calculation. Other options, such as the WSE offset, are optional and should only be used when necessary for your project.

The Channel Calculator will display a preview of the exit area cross section with normal and critical depth. When the Channel Calculator will save the values entered when exited. The values in the calculator can be changed later if needed.

The Channel Calculator in SMS gives you a useful tool for determining exit water-surface values for your SRH-2D projects. Try using it in SMS today!