Meshing M04 Draft

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Tutorial Description

Read the Tutorial Introduction before starting this tutorial which outlines the required links to download SMS, which will be use for mesh generation.

This tutorial is designed to introduce the skills required for creating a complex mesh, and builds on the skills introduced in Meshing Module 1, Meshing Module 2, and Meshing Module 3. Specifically, this tutorial includes:

  • Using SMS Toolbox to modify coverages and generate a floodplain mesh composed of quadrilaterals and triangle
  • Integrating essential floodplain elements, such as a low-flow channel, roads, and dams, into the mesh for accurate terrain representation.

The Going Further section demonstrates and outlines the benefits of generating a mesh using the constant paving density approach in the licensed version of SMS. All other sections of this tutorial can be completed in SMS Community.

This tutorial was developed using SMS 13.3.14.

Mesh Extent

The tutorial focuses on a inland floodplain. The mesh is 0.5 km² and includes a low-flow channel, roads, and dams.

M04 MeshExtent 001.png

Requirements And Downloads

Requirement Brief Description
Meshing Data Download the Meshing Module X Data Package MADDYTODO update link.
Assumed Knowledge It is recommended to complete the Meshing Module 1, Meshing Module 2, and Meshing Module 3 prior to completing this tutorial. If you run into any problems or need help, please contact support@tuflow.com

Prepare Your Working Environment

Unzip the required Data Package to your preferred working location, for example E:\TUFLOWFV\Meshing_M04.

  • The Complete_Mesh folder has the files for the completed tutorial.
  • The Module_Data folder has the files for the completed tutorial.
  • The Working folder is where files associated with mesh development will be saved.
M03 Mesh folder structure.png

Note: All file paths referred to will be relative to this base directory. For example, Complete_Mesh\Floodplain_001.2dm refers to E:\TUFLOWFV\Meshing_M04\Complete_Mesh\Floodplain_001.2dm.

Provided Project files

To save time and allow focus on meshing techniques multiple files have been provided.

Module_Data\Aerial Description
Aerial_Image.jpg Aerial imagery will assist in the generation of mesh. The spatial reference system is WGS84 / UTM zone 60s (EPSG:32760).
Module_Data\DEM
DEM_UTM_z60s.tif Digital elevation model of the model domain at 0.5m grid size. The spatial reference system is WGS84 / UTM zone 60s (EPSG:32760).
Module_Data\GIS
Model_Boundary_001.* GIS regions (polygon) layer that defines the model boundary and used to assist in the generation of mesh. The spatial reference system is WGS84 / UTM zone 60s (EPSG:32760).
River_Centreline_001.* GIS polyline layer that defines the channel centerline and used to assist in the generation of mesh. The spatial reference system is WGS84 / UTM zone 60s (EPSG:32760).
Road_Centrelines_001.* GIS polyline layer that defines the road centerlines and used to assist in the generation of mesh. The spatial reference system is WGS84 / UTM zone 60s (EPSG:32760).

*Multiple files with the same name as the shapefile but with a different file extension support a shapefile (e.g. .shx, .prj, .cpg, .dbf).

Set Up The SMS Project

Save The Workspace

Launch SMS and use the below steps and video to save the workspace in the Working folder:

1. From the menu bar select File > Save As.
2. Navigate to Working folder.
3. Save the workspace as Floodplain_001.sms.

Set The Workspace Projection

Set the projection WGS 1984 UTM Zone 60s from the menu bar Display > Display Projection....

Use the below steps and video to set the workspace projection:

  1. Go to Display > Display Projection....
  2. Select Global projection.
  3. The Horizontal Projection dialog will appear. In the Filter strings: type WGS 1984 UTM Zone 60s. Select the projection and OK > OK.

Load And Display The Data

Use the below steps and videos to open and set the display options for the provided files:

In the windows explorer navigate to the Module Data folder and drag the below files from the respective folders into the SMS workspace:

  • DEM/DEM_UTM_z60s.tif.
  • Aerial/Aerial_Image.jpg.
  • GIS/Model_Boundary_001.shp, River_Centreline_001.shp, and Road_Centrelines_001.shp.

Use the below steps and video to open and set the display options for aerial imagery:

  1. From the project panel right click on Aerial_Image.jpg and select Transparency....
  2. Update the transparency to 80%. Select OK.
  3. From the tool bar select Display > Lighting Options... .
  4. Under the Display Options Lighting tab check Enable lights. Select Ok. The display may take a moment to update.

Constructing The Mesh

Prepare Coverages

In this section GIS shape files are converted into SMS map data. Specifically the this section demonstrates how to convert the data and redistribute the vertices for each coverage.

Use the below steps and video prepare the model boundary coverage:

  1. From the Map Data panel right click on the Property Area and rename it Model Boundary.
  2. From the GIS Data panel right click on Model_Boundary_001.shp and select Convert > Shapes -> Feature Objects. Set the following:
    • In the GIS to Feature Objects Wizard -- Step 1 of 2 dialog check the Select coverage for mapping is set to Model Boundary and then under Select shapefiles to map the Model_Boundary_001.shp is checked. Select Next >.
    • In the GIS to Feature Objects Wizard -- Step 2 of 2 select Finish.
  3. Uncheck the shapefiles under the GIS Data panel and review the Model Boundary under the Map Data panel.
  4. Select Display Options DisplayOptionToolSMS.png and set the following in the Display Options dialog:
    • Select the point/Node dropdown and set the the colour to red.
    • Check the Vertex attributes are on and update symbol attributes to a crosshair symbol +.
    • Select OK > OK.
  5. Using the Select Feature Arc select the Model Boundary arc. Right click and select Redistribute Vertices....Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 2.0 and select OK.

Here the vertices have been redistribute by 2m to make it easier to connect the roads and river polygons to the boundary during the later stages of the tutorial. This vertex spacing will change before generating the mesh later.

Use the below steps and video prepare the river center line coverage:    

  1. Right click on the Map Data and select New Coverage.
  2. From the New Coverage dialog make sure the Area Property coverage type is select and rename it River Centre Line. Select OK.
  3. From the GIS Data panel right click on River_Centreline_001.shp and select Convert > Shapes -> Feature Objects. Set the following:
    • In the GIS to Feature Objects Wizard -- Step 1 of 2 dialog check the Select coverage for mapping is set to River Centre Line and then under Select shapefiles to map the River_Centreline_001.shp is checked. Select Next >.
    • In the GIS to Feature Objects Wizard -- Step 2 of 2 select Finish.
  4. Using the Select Feature Arc select the Model Boundary arc. Right click and select Redistribute Vertices....Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 3.5.
    • Check Use cubic spline and select OK.

Use the below steps and video prepare the road center lines coverage:    

  1. Right click on the Map Data and select New Coverage.
  2. From the New Coverage dialog make sure the Area Property coverage type is select and rename it Road Centre Lines. Select OK.
  3. From the GIS Data panel right click on Road_Centrelines_001.shp and select Convert > Shapes -> Feature Objects. Set the following:
    • In the GIS to Feature Objects Wizard -- Step 1 of 2 dialog check the Select coverage for mapping is set to Road Centre Lines and then under Select shapefiles to map the Road_Centrelines_001.shp is checked. Select Next >.
    • In the GIS to Feature Objects Wizard -- Step 2 of 2 select Finish.

Generate Low Flow Channel Polygons

This section demonstrates how to represent the low flow channel of the mesh using the SMS Toolbox. Specifically this section includes:

  • Converting feature arcs to polygons.
  • Setting the mesh type.
  • Generating the mesh.

Use the below steps and video generate the low flow channel polygon:

  1. Under the Map Data panel turn on River Centre Line and select the Toolbox Toolbox.png from toolbar.
  2. From the Toolbox dialog select Coverages and double click Polygons from Arcs.
  3. In the Polygons from Arcs dialog set the following:
    • From the Input coverage drop down select Map Data/River Centre Line.
    • Set the Average element/cell width to 3.0.
    • Set the Number of elements/cells (must be 1 or even) to 2.
    • In Output coverage name the new coverage River Centre Line Poly 2x3m.
    • Leave the rest as default and select OK.
  4. Select the History tab. Right click on the latest Tool history select Edit and update the name to Polygons from Arcs- River Centre Line 2x3m and Close the dialog. Relabeling the tool history simplifies identifying tools that need to be re-run and is particularly useful if you are doing a lot of processing in the Toolbox.
  5. Review the River Centre Line Poly 2x3m coverage.

Use the below steps and video generate the low flow channel mesh:

  1. Select the new River Centre Line Poly 2x3m coverage. Right click and select Type > Generic > Mesh Generator.
  2. Zoom into the downstream end of the channel. Using the Select Feature Arc tool select the end transition triangle and delete the arc.
  3. Repeat step 2 at the upstream end of the channel.
  4. Right click on River Centre Line Poly 2x3m and select Zoom to Coverage.
  5. From the Toolbar click Build Polygons Build poly.png.
  6. Using the Select Feature Polygon tool select the channel polygon. Right click and select Polygon Attributes....
  7. In the 2D Mesh Polygon Properties dialog set the Mesh type to Patch (quadrilaterals) and select OK.
  8. Right click on River Centre Line Poly 2x3m and select Convert > Map -> 2D Mesh. Accept the default name. Uncheck the map data and review the mesh. Earlier, the Polygon from Arcs tool was configured to create a polygon with an average cell width of 3.0 and the number of cells set to 2. This configuration has resulted in the creation of a low-flow channel mesh that is 2 cells wide, with each cell measuring 3 meters in length.
  9. Right click on the Mesh and select Remove > Yes.

Generate Road Polygons

This section demonstrates how to represent the roads within the mesh using the SMS Toolbox. Use the below steps and video generate the road polygons:

  1. Select the Toolbox Toolbox.png from toolbar.
  2. From the Toolbox dialog select Coverages and double click Polygons from Arcs.
  3. In the Polygons from Arcs dialog set the following:
    • From the Input coverage drop down select Map Data/Road Centre Lines.
    • Set the Average element/cell width to 3.0.
    • Set the Number of elements/cells (must be 1 or even) to 4.
    • In Output coverage name the new coverage Roads Centre Line Poly 4x3m.
    • Leave the rest as default and select OK.
  4. Select the History tab. Right click on the latest Tool history select Edit and update the name to Polygons from Arcs- Roads Centre Line Poly 4x3m and Close.
  5. Review the Roads Centre Line Poly 4x3m coverage and use the Select Feature Arc tool to delete the end transition triangles. There will be 5 arcs to delete in total.

Use the below steps and video generate a mesh of the roads:

  1. Right click on Roads Centre Line Poly 4x3m and select Type > Generic > Mesh Generator.
  2. From the Toolbar click Build Polygons Build poly.png.
  3. Using the Select Feature Polygon tool right click on the workspace and select Select All. Right click and select Polygon Attributes....
  4. In the 2D Mesh Multiple Polygon Properties dialog check Mesh types and set the type to Patch (quadrilaterals) and select OK.
  5. Right click on Roads Centre Line Poly 4x3m and select Convert > Map -> 2D Mesh. Accept the default name. Uncheck the map data and review the mesh. When finished right click on the mesh and select Remove > Yes.

Trim And Merge Layers

This section involves trimming the low-flow channel using road polygons, then merging the roads and channel into the same coverage.

Use the below steps and video to trim the low flow channel:

  1. Select the Toolbox Toolbox.png from toolbar.
  2. From the Toolbox dialog select Coverages and double click Trim Coverage.
  3. In the Trim Coverage dialog set the following:
    • From the Input coverage containing arcs to be trimmed select Map Data/River Centre Line Poly 2x3m.
    • From the Input coverage containing polygons to trim by select Map Data/Roads Centre Line Poly 4x3m.
    • Set the Trimming option to Trim to outside.
    • In Output coverage name the new coverage River Centre Line Poly 2x3m Roads Trim.
    • Leave the rest as default and select OK.
  4. Select the History tab. Right click on the latest Tool history select Edit and update the name to Trim Coverage- River Centre Line Poly 2x3m Roads Trim and Close.
  5. Review the new coverage and check that that the tool has trimmed the channel at the roads.
  6. Right click on River Centre Line Poly 2x3m Roads Trim and select Type > Generic > Mesh Mesh Generator.

Use the below steps and video to merge the coverages:

  1. From the Map Data panel select River Centre Line Poly 2x3m Roads Trim. Now holding Ctrl also select Roads Centre Line Poly 4x3m.
  2. Right click and select Merge Coverages. When the Do you want to delete the coverages used to make the merged coverage? message appears select NO.
  3. Rename the new coverage River and Roads Poly Merge and review the new coverage.

Clean The Merged Channel And Road Polygons

With the roads and channel now in the same coverage, the channel arcs can be connected to the roads, and the vertices redistributed to form a seamless mesh between the channel and the roads.

Use the below steps and video to snap the downstream channel arcs to the the road polygon:

  1. From the Map Data panel select River and Roads Poly Merge.
  2. Uncheck the GIS Data in the project panel and zoom into the road towards the downstream end of channel (refer to video).
  3. Using the Select Feature Point tool, select the point at the end of the channel arc and snap it to the nearest vertex along the road arc. Then reposition the point back to its original location (refer to video).
  4. Repeat Step 2 for the remaining 3 points on each channel arc (refer to video).

Use the below steps and video to redistribute and clean the vertices along the channel:

  1. Using the Select Feature Vertex tool delete the unnecessary vertex on the channel arcs downstream of the road. Reposition the remaining vertices to ensure they are approximately evenly spaced (refer to video).
  2. Repeat Step 1 on the channel arcs on the upstream side of the road (refer to video).

Use the below step and video to redistribute and clean the vertices along the road:

  1. Using the Select Feature Vertex tool reposition the vertices along the road polygon to ensure they are approximately evenly spaced (refer to video).

Use the below steps and video to redistribute the vertices along the feature arc:

  1. Using the Select Feature Arc tool hold shift and select both arcs perpendicular to the channel (refer to video). Right click and select Redistribute Vertices....
  2. Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Number of segments.
    • Set the Number of segments to 2 and select OK.

Use the below steps and video to snap the upstream channel to the the road:

  1. Zoom into the road towards the upstream end of channel (refer to video).
  2. Using the Select Feature Point tool, select the point at the end of the channel arc and snap it to the nearest vertex along the road arc. Then reposition the point back to its original location (refer to video).
  3. Repeat Step 2 for the remaining 3 points on each channel arc (refer to video).

Use the below steps and video to redistribute and clean the vertices along the channel:

  1. Using the Select Feature Vertex tool delete the unnecessary vertex on the channel arc upstream of the road. Then reposition the remaining vertices to ensure they are approximately evenly spaced (refer to video).
  2. On the downstream side of the road reposition the remaining vertices along the channel arcs to ensure they are approximately evenly spaced (refer to video).

Use the below step and video to redistribute and clean the vertices along the road:

  1. Using the Select Feature Vertex tool reposition the vertices along the road polygon to ensure they are approximately evenly spaced (refer to video).

Use the below steps and video to redistribute the vertices along the feature arc:

  1. Using the Select Feature Arc tool hold shift and select both arcs perpendicular to the channel (refer to video). Right click and select Redistribute Vertices....
  2. Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Number of segments.
    • Set the Number of segments to 2 and select OK.

Use the below steps and video generate a mesh of the roads and channel:

  1. Right click River and Roads Poly Merge coverage and select Zoom to Coverage.
  2. Right click on River and Roads Poly Merge and select Type > Generic > Mesh Generator.
  3. From the Toolbar click Build Polygons Build poly.png.
  4. Using the Select Feature Polygon tool right click on the workspace and select Select All. Right click and select Polygon Attributes....
  5. In the 2D Mesh Multiple Polygon Properties dialog check Mesh types and set the type to Patch (quadrilaterals) and select OK.
  6. Right click on River and Roads Poly Merge and select Convert > Map -> 2D Mesh. Accept the default name. Uncheck the map data and review the mesh.
  7. Right click on the Mesh and select Remove > Yes.

Trim Channel And Merge With The Boundary Coverage

In this section, the channel will be trimmed to fit within the model boundary. Then the roads, channel, and model boundary polygons will be merged into a single coverage.

Use the below steps and videos to trim the the channel and merge coverages:

  1. Select the Toolbox Toolbox.png from toolbar.
  2. From the Toolbox dialog select Coverages and double click Trim Coverage.
  3. In the Trim Coverage dialog set the following:
    • From the Input coverage containing arcs to be trimmed select Map Data/River and Roads Poly Merge.
    • From the Input coverage containing polygons to trim by select Map Data/Model Boundary.
    • Set the Trimming option to Trim to outside.
    • In Output coverage name the new coverage River And Roads Poly Merge Trim.
    • Leave the rest as default and select OK.
  4. Select the History tab. Right click on the latest Tool history select Edit and update the name to Trim Coverage- River And Roads Poly Merge Trim and Close.
  5. Review the new coverage and check that that the tool has trimmed the channel.

Use the below steps and video to merge the coverages:

  1. From the Map Data panel select Model Boundary then holding Ctrl also select River And Roads Poly Merge Trim.
  2. Right click and select Merge Coverages. When the Do you want to delete the coverages used to make the merged coverage? message appears select NO.
  3. Rename the new coverage Floodplain_001 and review the new coverage.

Clean Coverage

Having merged the roads, channels, and model boundary polygons into a single coverage, it is important to review and refine the polygons. The following section provides guidance on ensuring channel connectivity with the model boundary, adjusting the mesh resolution, and realigning model boundary to create a smooth, continuous mesh. Throughout this section it is important to follow and use the steps shown in the videos provided.

Use the below steps and videos as guide to connect the channel to the downstream model boundary:

  1. Zoom into the downstream boundary (refer to video)
  2. On the left bank use the Select Objects tool snap the channel node to the nearest model boundary vertex and move the node make into place (refer to video).
  3. Repeat step 2 on the right bank (refer to video).
  4. Use the Select Objects tool to select the feature arc perpendicular to the channel flow. Right click and select Redistribute Vertices....Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Number of segments.
    • Set an Number of segments to 2 and select OK.

Use the below steps and videos as guide to connect the channel to the upstream model boundary:

  1. Zoom into the Upstream boundary (refer to video)
  2. Using Select Objects tool snap the channel nodes to the nearest model boundary vertex (refer to video). Note you do not need to adjust the node location.
  3. Use the Select Objects tool to select the feature arc perpendicular to the channel flow. Right click and select Redistribute Vertices....Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Number of segments.
    • Set an Number of segments to 2 and select OK.
  4. Adjust the vertices along the channel arcs as necessary (refer to the video). Note when making these adjustments, consider the model resolution within the channel, aim for a smooth transition between cells, and evenly sized cells.

The alignment between the roads and model boundary needs to be adjusted to create a smooth continuous mesh. Use the below steps and video's to align the model boundary with the road:

  1. Zoom into the eastern boundary (refer to video).
  2. Using the Select Objects tool select the vertex along the boundary (refer to video) then right click and select Nodes < - > Vertices.
  3. Select the Select Feature Arc tool and delete the 3 arcs (refer to video).
  4. From the new node use the Create Feature Arc tool to digitise a feature arc to the road (refer to video).
  5. Using the Select Objects tool select the node along the new arc. Right click and select Nodes < - > Vertices (refer to video).
  6. With the Select Feature Arc tool select the new boundary arc (refer to video). Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 2.0 and select OK.

Continue to edit the mesh boundary with the below steps and video:

  1. Zoom into the eastern boundary (refer to video).
  2. Using the Select Objects tool select the vertex along the boundary and road (refer to video) then right click and select Nodes < - > Vertices.
  3. Using the Create Feature Arc tool digitise a Feature Arc between the new nodes (refer to video).
  4. Delete the arc parallel with the road boundary arc (refer to video).
  5. Using the Select Objects tool select the node along the new arc. Right click and select Nodes < - > Vertices (refer to video).
  6. With the Select Feature Arc tool select the new boundary arc (refer to video). Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 2.0 and select OK.
  7. Zoom out and review the mesh boundary along the road.

Continue to edit the mesh boundary with the below steps and video:

  1. Zoom into the lower eastern boundary (refer to video).
  2. Using the Select Objects tool select the vertex along the road (refer to video). Right click and select Nodes < - > Vertices.
  3. Repeat Step 2 for an additional 2 vertices shown in the video.
  4. Delete the arc between the new nodes (refer to video).
  5. Using the Create Feature Arc tool digitise a Feature Arc between the new node on the the road and eastern boundary (refer to video).
  6. Using the Select Objects tool select the node along the new arc. Right click and select Nodes < - > Vertices (refer to video).
  7. With the Select Feature Arc tool select the new boundary arc (refer to video). Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 2.0 and select OK.
  8. Repeat steps 5- 7 on the road and southern boundary (refer to video).

Redistribute Model Boundary

Redistributing the vertices can be used to adjust the mesh resolution in key areas, enhancing the model's accuracy while optimising runtimes. This targeted redistribution allows computational resources to be focused where they are most needed, ensuring a balance between model detail and performance efficiency. This section provides detailed instructions on how to modify the mesh resolution. Throughout this section it is important to follow and use the steps shown in the videos provided.

  1. Using the Select Objects tool select the vertex towards the southwest boundary road (refer to video). Right click and select Nodes < - > Vertices.
  2. With the Select Feature Arc tool hold shift and select the 4 boundary arcs (refer to video). Do not select any of the road arcs.
  3. Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 12.0 and select OK.

To increase the mesh resolution around the downstream channel use the below steps and video:

  1. Zoom into the downstream end of the channel (refer to video).
  2. Using the Select Feature Vertex tool, select the 10th vertex on the boundary arc, starting from the left channel arc node (refer to video). Then, right-click and select Nodes <-> Vertices from the menu.
  3. Repeat step 2 on the right side of the channel (refer to video).
  4. Using the Select Feature Vertex tool, select the 4th vertex on the boundary arc, starting from the left channel arc node (refer to video). Then, right-click and select Nodes <-> Vertices from the menu.
  5. Repeat step 4 on the right side of the channel (refer to video).
  6. Using the Select Feature Arc tool hold shift and select both outer arcs (refer to video). Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 8.0 and select OK.
  7. Using the Select Feature Arc tool hold shift and select both inner arcs (refer to video). Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 6.0 and select OK.

To increase the mesh resolution around the upstream channel use the below steps and video:

  1. Zoom into the upstream end of the channel (refer to video).
  2. Using the Select Feature Vertex tool, from the boundary arc select the vertex on the left of the channel arc node (refer to video). Then, right-click and select Nodes <-> Vertices from the menu.
  3. Repeat step 2 on the right side (refer to video).
  4. Using the Select Feature Arc tool hold shift and select both outer arcs (refer to video). Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 4.0 and select OK.
  5. Zoom out and review the changes made to the boundary.

Digitising The Dams

This floodplain model includes multiple dams throughout the catchment. This section demonstrates how to incorporate these features into the mesh.

Use the below steps and videos to include the dams within the model mesh:

  1. Zoom into the dam located towards the northwest boundary (refer to video)
  2. Using the Create Feature Arc tool roughly digitise around the dam (refer to video).
  3. Using the Select Feature Arc tool select the new arc. Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 8.0.
    • Check Use cubic spline select OK.

Use the below steps and video to include the 2nd dam within the model mesh:

  1. Zoom into the dam located towards the eastern boundary (refer to video)
  2. Using the Create Feature Arc tool roughly digitise around the dam (refer to video).
  3. Using the Select Feature Arc tool select the new arc. Right click and select Redistribute Vertices.... Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Specified spacing.
    • Set an average spacing of 8.0.
    • Check Use cubic spline select OK.

Generate And Edit Preliminary Mesh

Now that all the key elements and resolutions have been defined this section will demonstrate how to generate and review the mesh. The mesh review process is a critical step in any mesh development and often takes multiple iterations.

Use the below steps and video to generate the mesh:

  1. From the Map Data panel right click on the Floodplain_001 and select Type > Generic > Mesh Generator.
  2. Select Build Polygons Build poly.png from the toolbar.
  3. Using the Select Feature Polygon tool select the channel and road polygons (refer to video). Right click and select Polygon Attributes.... In the 2D Mesh Polygon Multiple Properties dialog check the Mesh type and from the drop down select Patch (quadrilaterals). Select OK.
  4. Right click and select Invert Selection.
  5. Again right click and select Polygon Attributes.... From the 2D Mesh Polygon Multiple Properties dialog check the Mesh type and from the drop down Paving (Triangles). Select OK.
  6. From the Map Data panel right click on the Floodplain_001 and select Convert > Map -> 2D Mesh. Accept the default name. Uncheck the map data and review the mesh.

A review of the mesh shows a thin triangle on a sharp bend of the low flow channel. Small mesh elements such as this can limit model runtimes and should be resolved to ensure optimal performance. We could manually edit this part of the mesh, however it's best to modify the map coverages to avoid the potential for mistakes.

Use the below steps and video to resolve the thin triangle:

  1. Zoom into the channel as shown in the video below and identify the thin triangle (refer to video).
  2. Check on the Floodplain_001 within the Map Data panel and delete the mesh.
  3. Using the Select Objects tool, select the vertex on the inner bank (refer to video) and right-click select Nodes <-> Vertices. Repeat this 3 more times on the vertices shown in the video.
  4. Select the Create Feature Arc tool and digitise 2 new arcs across the channel between the new nodes (refer to video).
  5. Using the Select Feature Arc tool hold shift and select the 2 new arcs (refer to video). Right click and select Redistribute Vertices....Set the following attributes in the Redistribute Vertices:
    • From the Specify drop down select Number of segments.
    • Set the Number of segments to 2 and select OK.

Continue to use the below steps and video to resolve the thin triangle:

  1. Using the Select Feature Vertex tool delete a vertex on the inner bank and adjust the remaining vertex along the bank (refer to video).
  2. On the outer bank use the Create Feature Vertex tool to create a new vertex between the existing two (refer to video). Use the Select Feature Vertex tool to Adjust the vertices on the outer as required to follow the bank line (refer to video).
  3. Select Build Polygons Build poly.png from the toolbar.
  4. Select the Select Feature Polygon tool and double click on the new polygon. The 2D Mesh Polygon Properties dialog will appear, set the following:
    • From the Mesh Type drop down select Paving (triangles).
    • Select Preview Mesh.
    • Select OK.

Use the below steps and video to generate and review the mesh

  1. Right click on the workspace and select Clear Selection.
  2. From the Map Data panel right click on the Floodplain_001 and select Convert > Map -> 2D Mesh. Accept the default name. Uncheck the map data and review the mesh.
  3. Check that the small element has been removed. Further adjustments to the vertices may be needed to produce a similar mesh shape shown in the video.
  4. Delete the mesh and make further adjustment to the vertices if required.

Assign Topography And Generate Mesh

This section outlines the process of applying elevation data and generating the final mesh, with the final step involving renumbering the mesh nodes and saving it as a .2dm file.

Use the below steps and video to assign elevation data and generate the mesh:

  1. Using Select Feature Polygon right click on the workspace and select Select All.
  2. Again right click and select Polygon Attributes.... From the 2D Mesh Polygon Multiple Properties dialog check Elevation (Bathy/topo) Type. From the drop down select Raster and then select Raster Options....
  3. The Raster Sets dialog will appear select DEM_UTM_z60s.tif and OK > OK.
  4. From the Map Data panel right click on the Floodplain_001 and select Convert > Map -> 2D Mesh. Accept the default name.

Use the below steps and video to review the assigned mesh elevations:

  1. Uncheck any open GIS or Map data from the Project panel.
  2. Select Display Options DisplayOptionToolSMS.png from the toolbar.
  3. From the dialog check Contours then select the Contours tab. Under the Contour Methods drop down select Color Fill and then OK.

Continue to use the below steps and video to review the assigned mesh elevations:

  1. Zoom into the mesh and use the Rotate tool Rotate Tool.png to view the mesh in oblique view (refer to video).
  2. To return plane view hit Shift + P.


Use the below steps and video to renumber the nodes and save the mesh:

  1. Make sure the Floodplain_001 mesh is selected from Mesh Data Panel.
  2. From the menu bar select Nodes > Locked. This will prevent any nodes being accidently moved.
  3. From the menu bar select Nodes > Renumber. This is an IMPORTANT step as renumbering will order mesh node and element IDs which which makes numerical calculation when modelling more efficient.
  4. To save the mesh as a 2D Mesh Files (*.2dm) select File > Save As. From the Save as type select 2D Mesh Files (*.2dm). Accept the default name Floodplain_001.2dm and Save.

Going Further (Optional)

This optional section demonstrates how to generate a mesh using the constant paving density feature of SMS.

Feedback

If you have any queries, feedback or requests for new functionality you would like added to the tutorial modules, please feel free to get in contact with support@tuflow.com.

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Conclusion And Next Steps

Well done on completing Meshing Module 4. You have now learnt the skills to build a real-world floodplain model mesh.

Return to the Tutorial Introduction Page to complete further meshing and model build tutorials.

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