Aquaveo & Water Resources Engineering News

How to Make an Unstructured Floodplain Mesh

Flooding can cause significant--and sometimes devastating--damage to infrastructure, crops, and commercial, residential, and industrial buildings. Unstructured floodplain meshes can be used to anticipate the most likely scenarios and plan prevention and mitigation accordingly. These are only some of the reasons why an unstructured floodplain mesh might need to be created. Your project may include multiple low lying areas that historically flood. You may need to see where berms or channels need to be adjusted to better accommodate sudden flow increases and prevent or mitigate flooding.

There are a few steps that should be taken anytime you model and simulate an unstructured floodplain mesh. SMS simplifies this process.

1. Import Background Data

The first step is usually to import elevation data from a scatterpoint dataset, raster objects, lidar data, mesh, grid, or from an existing project that includes the required elevation information for the floodplain. If the elevation data is not from a scatter set, it will need to be converted to a scatter set or interpolated to the mesh after the mesh is generated.

An aerial photo of the area can also be imported to help with visually referencing rivers, roads, and other structures.

2. Create a Mesh Generator Coverage

Once the elevation data has been imported, create a mesh generator coverage by right-clicking in the Project Explorer and selecting the New Coverage command. From the New Coverage dialog, select the Mesh Coverage type and enter a name for the coverage.

3. Create Feature Objects

The unstructured floodplain mesh will be generated from polygons in the mesh generator coverage. On the mesh generator coverage, create the enclosed arcs encompassing the area of the floodplain using the Create Feature Arc tool. Turn the enclosed arcs into a polygons by using the Build Polygons command.

4. Assign Mesh Type and Bathymetry

Use the Select Feature Polygon tool to double-click on each of your polygons. In the dialog that appears, assign the mesh type you want to create. You can use the Preview Mesh button to ensure your mesh will generate correctly.

After selecting the mesh type, select constant value or scatter set to use as the mesh elevation.

Once this is done for all your polygons, you are ready to generate your unstructured floodplain mesh.

5. Generate the Unstructured Floodplain Mesh

The process of generating your mesh is quite simple if the above processes are followed. Simply right-click on the mesh generator coverage and select the Convert to 2D Mesh command. SMS will start the calculations to create the mesh. Older versions of the software will bring up an options dialog where a few changes can be made to how the mesh is generated. For most projects, the default options are acceptable. A dialog will then appear asking you to name your mesh—the final step in creating the mesh.

Now you have an unstructured floodplain mesh. Explore the mesh to see if you like the results and get started on the rest of your project. You can adjust the display options at this point to make sure your mesh is satisfactory.

You can try out creating unstructured floodplain mesh generation in the SMS Community Edition for free.

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GMS 10.3 Beta Now Available!

A beta version of GMS 10.3, the next version of GMS, has been posted on our downloads page. This release includes a new model interface (MT3D-USGS), a much improved model interface (mod-PATH3DU), and lots of other enhancements, many of which were specifically requested by users. The full list of What's New can be found on the wiki, but here's a brief summary of some of the more noticeable changes.

Bigger icons for hi-res displays

One of the most immediately noticeable changes will be the new icons. The icons in GMS looked very small on some newer, higher resolution displays, so we've added larger versions of all the icons and GMS automatically switches to use the larger icons when it is run on a hi-res device. This effort involved an overhaul of almost all of our icons and some of them look noticeably different.

MT3D-USGS

This is a new model from the USGS which includes, among other things, transport calculations through the unsaturated-zone. GMS 10.3 includes an interface to MT3D-USGS and the interface is similar to those of the other flavors of MT3DMS.

mod-PATH3DU

The mod-PATH3DU interface has been improved and taken out of beta. Support for mod-PATH3DU version 1.1.0 including the new Waterloo method was added, as well as support for specifying DefaultIFACE, a model checker and a model wrapper, and the ability to create starting locations using a UGrid. More export options were also added including exporting pathlines to a shapefile.

MODFLOW Support

MODFLOW 6

The USGS recently released the next version of MODFLOW, MODFLOW 6, in beta and we are working hard to add support for it in the next version of GMS. For GMS version 10.3, however, the only MODFLOW 6 support is the ability to open a MODFLOW discretization file (.dis) and create a UGrid. Look for a more complete interface in the next version.

Map Shapefile to CLN

We've added the ability to create a CLN (connected linear network) from a shapefile. The CLN process is part of MODFLOW-USG but up until now it has not been easy to create this data in GMS. Using a 2D or 3D shapefile, GMS can automatically intersect the shapefile with the grid and create the CLN data. A new tutorial was created to demonstrate how this is done.

Zone flow for MODFLOW-USG ZoneBudget

Prior to version 10.3, GMS did not calculate the flow between zones or between selected cells for MODFLOW-USG models as it did with other versions of MODFLOW. This has now been implemented for MODFLOW-USG.

DISU data not recalculated

The DISU package data was being recalculated every time the model was saved, even if nothing had changed. This data can take a long time to calculate and save, so now GMS 10.3 will only recalculate the data if it needs to due to a change. For models that were created outside of GMS, the DISU data is never recalculated because the unstructured grids are often not suitable for these types of calculations (ie. vertices are not shared). The result is that these models are better supported in GMS because GMS no longer overwrites the correct DISU data with garbage data.

UGrids

Display Options per UGrid

Each UGrid can now have it's own display options. All of the UGrids are now listed in the Display Options dialog. Default UGrid display options are also available, which new UGrids inherit from. Options for one UGrid can be copied to other UGrids.

Splitting Layers

The ability to split a UGrid layer has been added, and is similar to this feature for 3D Grids.

Notes

As mentioned in a previous blog post, a new feature called "Notes" has been added which allows you to add notes to almost any object, including the project itself. This is meant to help document the modeling process as the model is being built. GMS can also automatically create notes about how new items were created. Notes include a timestamp indicating when the note was created.

Many other enhancements are included in GMS 10.3, including four new tutorials and lots of user requests. Some things are still not fully tested or complete, hence the "beta" status, but you are welcome to download GMS 10.3 and give it a try. Your feedback is welcome at support@aquaveo.com.

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MT3D-USGS in GMS 10.3

GMS 10.3 will include preliminary support for MT3D-USGS, a new transport model from the USGS that is based on MT3DMS and which allows for transport through the unsaturated zone, among other things. Here's a simple animation made in GMS showing a contaminant dropping through the unsaturated zone, hitting an aquitard, and spilling over the edges. This animation is based on a new tutorial that will be included with GMS 10.3 on how to use MT3D-USGS in GMS.

Animation of contaminant spill.

GMS 10.3 Coming Soon

It's been awhile since we posted any sprint reports, but that doesn't mean we've been enjoying a long vacation. GMS 10.3 is getting close to being done and the list of new features has been put on the wiki. There are a number of MODFLOW improvements, support for MT3D-USGS, major improvements to mod-PATH3DU (particle tracking for unstructured grids) and lots of other things including many user requests.

One user requested feature that will be in GMS 10.3 is the ability to add notes in various places in GMS. Notes can be added to objects like UGrids and coverages or to the project itself to help model developers remember where things came from or why they did things the way they did. GMS adds some notes automatically, like when an object is created from another object, like Map -> UGrid. All the notes can be shown, or just the user-created notes, or just the GMS-created notes. Here is an example of what it will look like.

GMS Sprint July and August 2016

Some of the more notable things completed by the GMS team during the month:

  • Multisampling (antialiasing) added in preferences
  • Fixed several bugs
  • Finished clip tool
  • Progress on new lidar functionality
  • Lots of refactoring
  • Released GMS 10.2 in beta
  • Documented new 10.2 features on the wiki
  • New notes functionality finished (in dev)
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GMS Sprint June 2016

Some of the more notable things completed by the GMS team during the month:

  • Fixed several bugs.
  • Finished PEST support for MODFLOW-USG
  • Added a "2D" constraint to UGrids for use with TINs, 2D Meshes and 2D Scatter objects
  • Added a "Fit to Active UGrid" command for grid frames.
  • UGrid cutaway views progress
  • Switched from Visual Studio 2010 to Visual Studio 2013
  • Much refactoring
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Advanced Run MODFLOW dialog

Typically when you run MODFLOW from GMS, GMS will run the version of MODFLOW specified in the MODFLOW Global/Basic Package dialog (shown below). The available MODFLOW versions in this dialog are those that ship with GMS.

With GMS 10.1 a new way to run MODFLOW from GMS was added. A new option called Use custom Run dialog was added in the MODFLOW Global/Basic Package dialog. With this option turned on, the Run MODFLOW dialog shown below is opened when you run MODFLOW. This dialog lets you pick which version of MODFLOW you want to run, including a custom MODFLOW version not supplied with GMS. It also lets you specify extra command line arguments that your custom MODFLOW may take. All the standard MODFLOW versions that come with GMS are also available and for those versions you can choose Double precision, Parallel, and/or 64 bit. The final command line that GMS will use to launch MODFLOW is displayed at the bottom of the dialog.

The Run MODFLOW dialog can also be accessed directly via a new menu command: MODFLOW | Advanced menu | Run MODFLOW.

This dialog is used in the new "mod-PATH3DU" tutorial, and the new "MODFLOW - Unsupported Packages" tutorial.

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GMS 10.1: MODFLOW CLN Process

New in GMS 10.1 is support for the CLN (Connected Linear Network) Process of MODFLOW-USG. From the MODFLOW-USG documentation:

The CLN Process was developed for MODFLOW–USG to provide the framework for incorporating one-dimensional connected features into a structured or unstructured threedimensional GWF Process grid. A one-dimensional CLN feature is any hydrogeologic or hydrologic water conveyance feature that has a cross-sectional dimension which is much smaller than the longitudinal flow dimension and the size of the encompassing GWF cell. Flow is computed in the longitudinal direction of the network of connected one-dimensional features using specified cross-sectional properties; flow between CLN cells and GWF cells is computed across the wetted perimeter of the one-dimensional CLN feature. The CLN Process thus provides a mechanism for including features with small cross-sectional areas, relative to GWF cell sizes, without having to build this level of detail into the grid used for the GWF domain.

A new tutorial was created that introduces the CLN process interface in GMS, and a page was added to the wiki. CLN wells can be created a conceptual model, mapped to the grid, and edited on the grid.

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GMS Sprint May 2016

Some of the more notable things completed by the GMS team during the month:

  • Fixed several bugs
  • Simplified multi poly mesher input
  • Progress on merging GMS and SMS datasets
  • MODFLOW DRN package in sqlite
  • Lock/unlock UGrid for editing
  • Progress on PEST for MODFLOW-USG
  • Bounding grid frame for UGrid points
  • Text import of UGrid points
  • Antialiasing display investigations
  • UGrid cutaway views progress
  • Lots of refactoring
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GMS 10.1: Name File Dialog, Support for Unsupported Packages, Running Other MODFLOW Binaries

GMS 10.1 adds the "Name File" dialog, which adds the following new capabilities:

  • Unsupported packages (packages that don't have an interface in GMS) can be included in the solution and edited in a text editor
  • Unsupported packages can be removed from the simulation
  • Unit numbers are no longer altered by GMS
  • Unit numbers can be set by the user

An example of the Name File dialog in use is shown below. In this example, a MODFLOW-CFP model was imported into GMS. Although GMS does not have an interface for the MODFLOW-CFP packages included in the model, those packages are still part of the simulation and are listed in the dialog. The input files for those packages can be edited from the dialog (using a text editor), or the packages can be removed from the simulation. But there is no need to remove the packages from the simulation because GMS 10.1 comes with a MODFLOW-CFP binary that can read the MODFLOW files that GMS writes. So this model can be run from GMS, and the solution, including the MODFLOW-CFP parts, can be displayed in GMS. This illustrates how GMS 10.1 includes better "support" for unsupported packages.

Name file / unit manager
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