WMS

How and When to Use Depression Points in WMS

By aquaveo on September 19, 2018

Have you ever wondered what depression points are used for? Should you be including them in your watershed delineation? Depression points can greatly help to improve the accuracy of your model when used correctly.

A depression point is significantly lower than its surrounding elevation, causing a change in flow accumulation and direction. An example of a depression area would be a watershed that contains a mine. TOPAZ is a public domain program that is used in computing flow directions and accumulations for use in basin delineation with DEMs. TOPAZ assumes that all depression points it encounters in its calculations are due to a lack of resolution, and therefore “fills” the depression point in increments until a flow path can be established straight across the low point. In order to view how a natural depression point would affect flow direction and accumulation, it is necessary to define the specified areas as depression points. This causes TOPAZ to read the cell as a NODATA cell, making TOPAZ think it is a DEM boundary instead of raising the elevation in the depression. Comparing a before and after of marking a depression point shows how the flow path is affected by depression points as displayed below.

It is appropriate to use a depression point where a natural depression occurs in the horizon. Typically you would only define depression points for larger areas where the flow path will be significantly affected by the area. It is not always necessary to define a depression point however. You want to use it when you receive straight lines for delineation boundaries for instance. This would most likely be caused by undefined depression points.

Some errors can occur however when defining depression points incorrectly.

Sometimes users will mark the bottom elevation that is actually up higher to the side of the depression point and is not exactly the center deepest point. This issue can be avoided by using the Set contour min/max tool in the Terrain Module to correctly identify the absolute bottom elevation. This DEM point is the one which should be marked as a depression point.
Another incorrect use of depression points would be to use them to outline where a stream bed is. A stream bed can be identified by using stream arcs in WMS.

Now that we’ve established when and when not to use depression points, you might be wondering how to create depression points in WMS. To create depression points in WMS:

Turn on the Terrain Data Module.
Use the Select DEM points tool to select the cell containing the lowest DEM elevation. If working with an area that has a large natural depression, simply hold down the Shift key to select all of the cells with low elevation at once.
Select DEM | Point Attributes to bring up the DEM Point Attributes dialog.
Turn on Depression point to mark the cell as a depression point.

Now that the depression points are set, you can run TOPAZ to view the new flow paths. TOPAZ will recognize the new depression, and the detention basin calculator can be used to create a stage-storage curve.

Try adding depression points in your WMS model today!

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WMS

4 New Features in the WMS 11.0 Beta

By aquaveo on August 29, 2018

For the last couple years, we’ve been working hard on the next version of WMS, and the beta for version 11.0 has now been released!

To help you learn about some of the new features, we’ve compiled this list of four new features in WMS 11.0 Beta.

The first big improvement is a streamlined and updated set of floodplain delineation tools. Due to a lot of under-the-hood work, some of the delineation processes have been sped up by a factor of 10! This can greatly reduce the amount of time you spend on these projects.
WMS 11.0 Beta now supports Amazon Terrain Tiles. These are high resolution digital elevation model (DEM) tiles for every location around the world, and the resolution goes as high as 3 meters per pixel. A digital elevation model is simply a two-dimensional array of elevation points with a constant x and y spacing.These DEM tiles can be accessed through the Import from Web and Get Data tools in WMS.

Through a new dialog, WMS 11.0 Beta now offers better support for managing and editing cross section databases in HEC-RAS models. HEC-RAS is a one-dimensional model for computing water surface profiles for steady state or gradually varied flow. You can select, import, export, manage, and edit cross sections and cross section databases more easily.
The hydraulic modeling module has been updated to be able to import and export LANDXML files for the Storm Water Management Model (SWMM), HY-12 (a storm drain analysis program used for designing inlets, pipes, and general storm drain network layouts), and EPANET (a widely used water distribution model developed by the US Environmental Protection Agency).

These are only some of the many great new and updated features in WMS 11.0 Beta. You can find a bigger list of them here. Try out the beta by downloading it today!

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WMS

Converting Units

By aquaveo on August 22, 2018

Seeing which units are being used in a project or for a particular object within the project is fairly easy. Converting the units from, for example, U.S. feet to meters, can introduce problems into a project if you do not do it in the correct way.

Reproject

Reprojecting the data involves moving the data from one coordinate system to another. So if your data is in a UTM coordinate system in meters and the rest of your project is in a State Plane projection that uses U.S. survey feet, reprojecting can change the data to match. Conceptually, the data will remain in the same location, but the data will be adjusted to the new units.

To reproject a dataset:

Right-click on the dataset in the Project Explorer and select Reproject.
In the Reproject dialog, the current projection is shown on the left. On the right side, set the new projection and units.

When converting units through reprojection, keep in mind that Z values (elevations) don’t always convert correctly. Round off errors sometimes occur when reprojecting data. In general, reproject does well in changing the X and Y units. The Z value, if it has been set as the bathymetry, typically also converts units well using the reproject option. Other datasets often do not convert between units using the reproject method.

When converting from rasters to scatter sets, the elevation is usually recognized and converted correctly.

Dataset Calculator

Datasets units can be converted using the Dataset Calculator. This is often necessary when the data has been reprojected, but not all of the datasets can be converted using that method. For example, a velocity dataset or conductivity data.

To convert a dataset with the Dataset Calculator:

Select the desired dataset in the Project Explorer.
Select the Data Calculator macro, or the Data Calculator command or the Dataset Toolbox command in the Data menu.
Select the dataset to convert, then multiple or divide the dataset by the conversion value.

There are a few numbers it is useful to have when doing these conversions:

0.304800609601 meters is equal to one U.S. Survey foot
3.28083333333 U.S. Survey feet are equal to one meter
0.3048 meters is equal to one International foot
3.28083989501 International feet are equal to one meter

Note that there are many datasets that will not work with the Data Calculator.

In the end, make certain all the data being used in your model is in the correct units. Having mismatched units will typically create model errors and generate inaccurate results.

Try reprojecting data or using the Data Calculator to convert units in GMS, SMS, or WMS today!

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WMS

Visualizing Meteorological Data

By aquaveo on August 1, 2018

Do have rainfall data you would like to visualize in WMS? Inside WMS there are a couple tools to make your rainfall data visually interesting.

After you have imported your precipitation data, such as NEXRAD data, you can adjust your display options and/or create an animation.

Adjusting the Display Options

Use the Display | Display Options command to open the Display Options dialog.
Adjust your display options to show the data you want captured. It is recommended to turn on the Contours options.
If using the Contours option, right-click on your rainfall dataset under 2D Grid Data and select Contour Options to open the Contour Options dialog.
Adjust the contour method and interval to best display your rainfall data.
With the down arrow key on the keyboard, step through the time steps in the properties window on the right sidebar to see how the precipitation varies.

Creating an Animation Loop

Select your rainfall dataset in the 2-D Grid Module. The selected dataset will be used to create the film loop and can be cumulative or incremental. View incremental rainfall datasets in the same way as cumulative datasets.
Select the Data | Film Loop command to open the Film Loop Setup Wizard. This wizard needs to be opened with the 2-D Grid Module active in order to have access to the meteorological data options.
The first step in the Film Loop Setup wizard is essentially the same as creating any other animation through WMS. Select the location where the animation file will be saved and the type of film loop to generate.
The second step of the Film Loop Setup wizard is to set the desired time step options for the rainfall data.
The final step is where you will finalize the display options of the animation, and click Finish.
WMS will take a few moments to create and save the animation file. The animation will start playing as soon as the saving process is complete.

When all is done, you can view your animation using the AVI play provided with the WMS installation, or you can use another application, such as GoogleEarth. The animation will display the movement of the storm through the selected time steps.

Try visualizing meteorological data in WMS today!

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WMS