SMS

Understanding SRH-2D Obstructions

By aquaveo on February 2, 2022

Do you have an SRH-2D project that might benefit from using obstruction objects? The obstruction coverage in SMS allows you to add obstruction objects to your SRH-2D project. Using obstructions in some cases can be beneficial, but there are a few key ideas to keep in mind. This post will cover some of these.

Adding obstructions to an SRH-2D project involves creating a coverage assigned as an SRH-2D obstruction type coverage. On this coverage, you can draw arcs and points to act as obstruction objects. Each arc and point can be assigned obstruction attributes. Finally, the obstructional coverage can be added to the SRH-2D simulation to be used in the model run.

Example of the SRH-2D Assign Obstructions dialog

First, it is important to understand how obstructions interact with the model run. Obstruction objects on the obstruction coverage will reduce the flow of water through the model by applying a drag force. Water will not flow around the obstruction but will instead be slowed by the drag force of the obstruction. The assigned attributes on the obstruction object will determine which cell nodes on the mesh will be assigned as an obstruction. Obstructions can be used for items like bank protrusions and boulder clusters.

Second, when assigning obstruction attributes to an obstruction object, a width/diameter is specified in SMS. For point obstructions, this user-specified value is then converted by PreSRH-2D to a radius for SRH-2D. The SRH-2D model applies the radius around the point. For line obstructions, the arc definition and width are converted by PreSRH-2D to point locations that define the obstruction area. That means, for example, if you assign an arc to have an obstruction width/diameter value of 2 meters, then 1 meter on one side of the arc and 1 meter on the other side of the arc will be the obstruction area.

Third, obstruction objects can be assigned a drag coefficient, porosity, and a specific thickness. It is important to note that obstruction objects are not meant to completely impede the flow of water.

For items that completely block the flow of water, such as bridge piers or buildings, a void in the mesh should be created that models the area of blockage in most cases. Likewise, having a large number of obstruction objects in your model sometimes can cause issues with the SRH-2D model run and therefore it is recommended that obstruction objects be used judiciously.

Obstructions can be a valuable addition to your SRH-2D model. Try using obstructions with SRH-2D in SMS today!.

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Understanding the Smooth Datasets Tool in SMS

By aquaveo on January 12, 2022

Do you have a dataset, or survey data, that has random distances between points which you would like to have a more uniform distribution? SMS contains a tool that allows you to smooth data. By using the Smooth Datasets tool you can create a new dataset that has a more even distribution.

To use the Smooth Dataset tool, do the following:

  1. Make certain you have the Scatter module containing the dataset active. If your dataset is in a different geometry, it may need to be converted to a scatter set.
  2. Use the Dataset Toolbox command in the Data menu to open the Dataset Toolbox.
  3. Select the Smooth Dataset tool under the list of tools.
  4. Enter the parameters for smoothing the dataset.
The Smooth Datasets tool in the Dataset Toolbox

When using the Smooth Dataset tool there are a few items to keep in mind:

  • There are no restrictions related to X or Y point distribution. In other words, the dataset points don’t need to align with a grid.
  • The "Element Area Change" option is only recommended when smoothing size functions for certain meshing methods (i.e. scalar paving).
  • When smoothing elevations, the "Maximum slope" method is recommended. This function works with any scalar dataset, but I will assume elevation as the dataset for this explanation.
  • When using the "Maximum slope" method, the elevation of a starting point is compared with its neighboring points (connected via triangles). The elevation of a neighboring point is adjusted if the slope between the points exceeds the specified maximum.
  • The "Anchor type" determines the starting point.
  • If "Minimum value" is selected, SMS starts at the point with the lowest elevation, and the elevations of its neighboring points are adjusted if necessary. SMS then continues to the point with the next lowest elevation.

The Smooth Dataset tool can help you resolve issues with raw data and help your model be more efficient. Try out the Smooth Dataset tool in SMS today!

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SMS

Using Arc Annotations in SMS

By aquaveo on December 22, 2021

Have you been wanting to have more contextual information for your arcs in SMS? Some projects require being able to easily tell which direction arcs are flowing or quickly see the distance of arcs. With the release of SMS 13.1, you may have noticed an addition to the display options that can help with this. The Arc Annotations options can provide additional contextual information to arcs in your SMS projects. This post will review how they can be accessed, and how they can help you while modeling in SMS.

The options for arc annotations are contained within the Map tab of the Display Options dialog. The Map tab can be accessed either by selecting Map from the list within Display Options, or by right-clicking on Map Data in the Project Explorer and selecting the Display Options… command. Once in the Map tab, the Annotations option can be turned on, which will then activate an Options… button. Clicking this button will bring up the Arc Annotation Options dialog where the new arc annotation options can be selected.

The main options that can be set here involve direction and ticks. Direction will show arrows on arcs to indicate which direction they are flowing. Ticks will show tick marks on arcs to indicate length measurements, which can help in visually seeing the real-world length of arcs. There are multiple options when it comes to how ticks will be displayed, giving you flexibility for your specific needs when it comes to modeling. It is important to note, however, that ticks will only display if the project units are set to feet or meters.

Example of the arc annotations

These features can be valuable in projects where the added visual cues and references can help with more instantaneously interpreting the graphical data. The customizability for tick display will also allow for the optimization of making this information look as presentable as possible within the model. For more details on the options available when using arc annotations, visit the XMS Wiki to learn more!

Try out using arc annotations in SMS 13.1 today!

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Best Practices for Extracting Features

By aquaveo on December 1, 2021

Have you used the Extract Features tool in SMS before? The Extract Feature tool lets you generate channel and bank arcs from elevation data. There are some tricks to optimizing the use of this tool. This post will review some of the best practices that you should follow when you extract features from elevation data in SMS.

Digital Dams
Example of a digital dam

These are often artifacts from stamping channels or unprocessed LIDAR data and they can cause problems determining flow directions on the raster. The pre-processing engines (TOPAZ and TauDEM) fill these prior to computing flow directions, which can be a problem if the centerline strays from the thalweg and matching depth is computed off of the filled raster and not the original, which will also cause higher elevations along the channel above the dam. These can be fixed by either:

  • Trimming the raster above the dam by right-clicking on the raster and selecting Convert To | Trimmed Raster using a Map Module polygon.
  • Modifying elevations downstream of the dam to match correct stream thalweg elevations by right-clicking the raster and selecting Editing | Edit Raster using selected arc elevations.
Placing Points for Extracting Bank Features

When extracting bank features, place the point closest to the most important area. For example, if a section is being used for bridge analysis, place the point close to the bridge. This allows the bank lines to stay the closest to the original feature. If the Extract Bank tool misses a bank section, try moving the point to the missed section and run it again.

Extracting Centerlines for Braided Streams

When extracting centerlines for braided streams, sometimes they may not follow the actual stream location because of digital elevation model inaccuracies. When this happens, extract both centerlines and manually merge the arcs into a single arc after both centerlines have been extracted.

Use the Depth That Is Option

The following guidelines should be observed when using the "Use the depth that is" option:

  • If there is a single well-defined channel with a strong bank feature, use the "Closest to centerline" option.
  • If there are multiple floodplain bank features, use the "Closest to previous" option, otherwise, the Extract Features tool may catch a different floodplain feature.
  • If there are multiple channels or a braided stream (and you want to catch the widest extents of the channel), use the "Furthest from centerline" option.

Try out some of these best practices while extracting features in SMS 13.1 today!

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