Objective - This tutorial will take the user through importing land cover data, importing precipitation data, setting up a plan, and computing results.

Data Files

The data for this tutorial are provided below.
Land Cover and Precip Workshop.zip

If you are in the class, you can get the data files from the Development Tools:

These data are for demonstration purposes only and should not be used for engineering analysis.

Steps

Define a Spatially Distributed Surface Layer of n Value

Defining spatial roughness requires the use of two layers:

  • A Classifications Layer that defines the spatial distribution of different land covers, features, or land uses
  • A n Value layer that associates the cover types in the Classification Layer with roughness values
  1. Start by defining a Classification Layer.
    1. Click the "+" on the Surface Layers tree node.
    2. Choose Add a new classification layer to the project option
    3. Click on the Classifications tree node.  
    4. Choose the Components tab on the right pane.
  2. Let's start by importing the NLCD land cover grid.
    1. Press the Import NLCD (2021) button.

      The model extent is mostly evergreen forest (n=0.12) with some development and some shrubberies.  

    2. The tool will clip a raster coverage of these data to the model extent and add it as a file called "nlcd_clipped."

  3. Next, let's augment this raster coverage with some with some classification polygons.
    1. First draw a polygon 
      1. Select Classification Polygons and the Edit tool.
      2. Draw a polygon to represent a new neighborhood.
      3. If you clear the NoData name you will get a list of common land use types.  Select Developed Medium Intensity.


    2. Next let's import a river corridor polygon.
      1. We don't actually have a digitized river corridor polygon, but we do have a Conceptual Mesh region that will work. 
      2. Click on the Conceptual Mesh and select Region 1 either by clicking on it or in the Regions list in the Components pane.
        1. To select a feature, you should have either the Selection tool or Edit tool selected. (Not the Pan tool.)
      3. Right click on the highlighted (pink) region and select Copy → Region Polygons and Region Metadata. 
      4. Click on Classification
      5. Right Click on Classification and select Paste Feature

      6. The new polygon will show up in your list of Classification Polygons in the Classification Components tab.
      7. This is an ephemeral mountain channel.  "Open Water" doesn't exactly describe it and the default channel n value won't be appropriate.
      8. Give it a unique name like "River Corridor"

  4. Now that you have a land classification you need to associate n values.  There are two ways to define n values.  You can create a new n Value Surface layer and select the Classification, or you can just push the button.
    1. Press the + Create N-Value Layer from this button.  
    2. When you select this new n Value surface layer, it will populate default roughness factors for every land use type you have...except for River Corridor, since we made that one up.
    3. You can see it adopted an n value of 0.06 for Developed, Low Intensity, but you will have to type in your River Corridor value.
      1. Give River Corridor an n value around 0.05.
    4. Make sure the Geometry is associated with your terrain and n Value layer.
      1. Click on the geometry
      2. Click on the Components pan on the right.
      3. Select the Terrain and n Value layer from the drop down menus.


Add a Precipitation Boundary Condition

  1. Open BC and Results Workshop
  2. Create a new boundary condition by pressing the "+" button next to Boundary Conditions.
    1. Name it "Rain on Mesh"
    2. Give it the time window pictured below
    3. Press Create.
    4. Select the Precipitation layer beneath your boundary condition and turn Precipitation on over in the Components tab.
      You can define a constant precipitation here, but we are going to import some gridded precipitation data.
    5. Select Constant and switch to Gridded


    6. Press the button to select data:
    7. The gridded rainfall editor will open.  Press the Select Files button.
    8.  Navigate to the Precip_Mar2023_1hr
    9. Select all the GRB2 files (all but the top two text files)
    10. This will load and order these rainfall grids.  You can move the red line to animate.  
    11. Press Import to bring them into your model.
    12. When your model comes in, you can animate your Precipitation
            Precip Animation.mp4
      1. Select the Precipitation Layer of your Boundary Condition Group and use the arrows to animate
      2. Note: You may need to click away and back to the Precipitation Layer before you animate.
  3. Give the model a downstream boundary condition.  
    1. Draw a boundary condition line at the downstream end of the mesh.
    2. Specify a normal depth boundary condition (Slope~0.008).

Create a Plan and Run

  1. Press the "+" button next to the Plans group to create a new plan.
    1. Select your Geometry and Boundary Conditions and adopt the boundary condition Time Window (by default).  
    2. Press the Create button.  
  2. If you see this error, you need make sure your n Value and terrain are associated with your Geometry.
  3. Select your Geometry and Boundary Condition.
  4. This model takes a long time to run, so we are only going to run the first 36 hours
    1. Change the Time Window in the plan to Custom
    2. Run the model for the first 3 days (which include the biggest flow) as pictured below.
    3. Switch to the Diffusion Wave computational engine 
    4. Compute

Review your results (you will be able to view your results before the project finishes running).

ROM.mp4

Solution Files: Land Cover and Precip Solution.zip