WMS

Easily Snapping Outlet Points to Stream Arcs

By aquaveo on November 5, 2024

When creating your Watershed Modeling System (WMS) project, did you find that your outlet point isn’t in the right place on the stream arc? Outlet points are placed at the points of confluence in a watershed. Designating an outlet point is necessary for delineating a watershed, but it must be placed correctly. The Snap Outlet Points to Streams tool, found in the Toolbox, can help place the outlet points in the correct locations.

Example of a point that is not snapped to the streams

If an outlet point is near but not on a stream arc, WMS can automatically snap an outlet point to the stream, or the stream arc to the outlet point, within a very limited range, depending on which was created first. But if two stream arcs are close together, and the outlet point between them, the auto-snapping may place it on the wrong stream arc, thus making the watershed delineation incorrect. Or, the outlet point may be placed far enough away from the stream arcs that WMS can’t automatically snap it to the appropriate stream arc for watershed delineation. When an outlet point is placed incorrectly, it can cause problems for your model. Either the watershed delineation will fail, or the basins created could have incorrect boundaries. This is where the Snap Outlet Points to Streams tool can be useful.

The Snap Outlet Points to Streams tool will allow you to place outlet points away from the stream arcs but still snap them to a stream. It allows you to define how far away from the outlet point to look for a stream arc. While you still should be cautious about outlet point placement, it gives you a little more latitude in creation locations to ensure the correct delineation of the watershed.

To find the Snap Outlet Points to Streams tool, you will need to look in the Toolbox under the Coverages folder. When you open it, you will choose the input coverage containing the outlet points, and also, the input raster streams file. You will need to define the maximum distance in map units for the tool to search for the stream arcs to snap to. After entering a new coverage name for the output coverage to be created, you can run the tool.

Head on over to WMS and try the Snap Outlet Points to Streams tool today!

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WMS

Announcing WMS 11.3 Beta!

By aquaveo on September 24, 2024

We are pleased to announce the release of WMS 11.3 in beta! Our developers have been working on several updates to the Watershed Modeling System (WMS). They have added some new features and improved the functionality of others. We'll highlight a few of them here.

GSSHA Permafrost

We are pleased to share that we have now added the ability to model permafrost regions with the GSSHA numeric model in WMS 11.3. With the addition of permafrost options to GSSHA models, your. Permafrost parameters can be defined and set under the GSSHA menus, Job Control and Map Tables. Also when you select a Feature Point/Node and right-click on it and select Attributes to open the Properties dialog. Output graphs and reports on soil temperatures can be generated for further analysis.

Feature Objects Clean Option Updates

We have made several improvements and updates to the Clean Option in our Feature Objects menu. Our developers have improved the cleaning algorithm, so that it is now significantly faster on large coverages. This will improve the efficiency of your model runs.

The Clean Option user interface has also been completely updated. It has the same functionality as the old interface but it now contains more options giving you more flexibility. You can choose to clean all feature objects or only selected ones. You can also now choose to do a full clean on feature objects, or only selected types of clean up.

Search Box for Recent Files

We have also added a search box to the Recent Files dialog. WMS shows the 5 most recent projects you have worked on when you click on File. When you click "More…" below that list of five projects, the dialog that comes up now includes a search box at the top. Rather than scrolling through the list of recent projects, you can now use the search box to find your modeling project more quickly.

These are only some of the great new and updated features in WMS 11.3 beta. Head on over to Aquaveo and try out the WMS 11.3 beta today!

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WMS

Tips for Manually Editing Stream Arcs

By aquaveo on August 13, 2024

Did you generate stream arcs in your Watershed Modeling System (WMS) model that you discovered later needed to be adjusted? Or maybe the outlet point’s position needs to be slightly adjusted. You can manually edit streams without using any of the wizards available in WMS, but you do need to be careful. Here are some tips on how to do it and what to watch for.

To manually edit your stream arcs, you will need to use the tools in the Map module. You can select and move a stream node or vertex to alter the path of a stream. You can also change a node to a vertex, create new feature points where needed, and manually edit properties in the Properties screen. You may wish to change your Display Options so that you can see the stream arcs, and vertices more clearly. Used carefully, you can make minor adjustments without using the wizards.

If you need to shift a stream outlet point or other major node, you can use the Select Feature Point/Node tool to select the stream outlet point and drag it to a new position. When the stream outlet point is originally on an arc but then moved away from the arc, the arc can snap to the new outlet location. Be careful where you move your stream outlet point, (or any stream arc vertex), especially if you accidentally shift it to a higher elevation, as this can create digital dams or break the model.

If you have extremely long stream arcs, or need to make precise corrections around obstacles, land formations, or buildings, you can manually add one or more vertices to the arc using the Create Feature Vertex tool. Then, you can then use the Select Feature Vertex tool to select and move them to better locations within the bounds of the model. This can be especially useful if you discover that one or more of your steam arcs now cross outside the bounds of the delineation arcs after manually editing them.

If you’ve changed a stream arc by adding vertices or just moving locations, you’ve also changed the vertex distribution along the arc. It may be necessary to redistribute the vertices again.

You will want to check elevation values against the DEM. If you have moved a stream arc point, you may have shifted it from its elevation. You may need to re-interpolate elevations back onto the stream arcs.

It is also recommended that manual edits be done prior to defining the model, otherwise you may discover that making these edits, while improving the stream arcs, has broken the model. If that happens, you may need to re-delineate the watershed. You can go back to the wizard that you used to delineate your watershed model and skip to the appropriate step to rework your model from there.

This manual editing of stream arcs is different from the GSSHA’s Smooth Stream/Pipe Arcs tool and works outside of any wizards within WMS.

Try out any of the tips with your watershed projects in WMS today!

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WMS

Discover MODRAT Percent Impervious

By jcreer on July 2, 2024

When working with the Watershed Modeling System (WMS) and the MODRAT model, one potential aspect of your watershed analysis would be determining the percent impervious values for each sub-basin. Accurate percent impervious calculations may significantly influence your hydrologic modeling outcomes. Here is a guide to help you navigate this process effectively.

Importing Land Use Data

To compute the percent impervious for each sub-basin in MODRAT, you need to start with accurate land use data. Land use data in WMS is typically stored in the GIS and Map modules. The most efficient way to read this data into WMS is through a shapefile. Here’s how you can do it:

Example of the Map MODRAT Attributes dialog

Create a Land Use Coverage: In WMS, start by creating a new land use map coverage. This coverage will hold all the land use data you import.
Import the Polygon File: Import your land use polygon shapefile into WMS. This file should contain various land use types and their respective boundaries.
Assign the Percent Impervious Field: Ensure that the percent impervious field, often labeled as IMPERV_ by the Los Angeles County Department of Public Works (LACDPW), is correctly mapped to the LA County Soil land use field in WMS. This step is crucial as it links the impervious data to your land use coverage.
Compute and Assign Percent Impervious: With the land use data now present in WMS, use the "Map Attributes" command in the MODRAT menu to compute and assign the percent impervious values. This function will analyze the land use data and calculate the percent impervious for each sub-basin.

Using Coverage Overlay Options

Another method to determine the percent impervious values is by using the Coverage Overlay options in WMS. This approach is similar to calculating curve numbers and involves overlaying land use coverage with drainage coverage.

Overlay Land Use and Drainage Coverage: Start by overlaying your land use coverage with an existing drainage coverage. This will combine the datasets, allowing for an analysis of land use types within each drainage area.
Calculate Percentages: The overlay will provide you with the percentages of different land use types within each sub-basin.

Whether you choose to import land use data directly or use the coverage overlay options, both methods can aid in determining the percent impervious. Use either method in your MODRAT projects in WMS today!

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WMS