Adding Terrain, Mods, Land Cover, and n Values

Objective: Learn how to download, import, and reorder terrain data, add land cover, import channel mods from 6.x.

Data Files

The data for this tutorial are provided below.

Terrain LC Wksp Starting Files.zip

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

Steps

Step 1: Set Up and Georeference a New Model

We will create this model from scratch, so open HEC-RAS 2025
Select New Project
Give the project a name.
You will need a projection to get started. We have provided you a shape file of the model location. You can drag the Model Boundary.prj file over to the box called Drop a File Here
Press the Create button
To locate yourself on the map, drag the shape file Model Boundary.shp into the map.
It will show up under Map Layers
Right Click on the Model Boundary Map Layer and select Zoom to Extent
Drag shape file.mp4
The map should center on the shape file, taking you to your river location.

Step 2: Import USGS Terrain Data

Scroll down in the tree and add a new terrain by pressing the "+" button on Terrains
Name the new Terrain ("Import USGS" makes sense)
Hover over the new Terrain Entry and press the "+" button to add data
Select Download USGS terrain tiles directly.
This launches the USGS Terrain Importer. Select Query Area to see what is available.
The USGS server is often offline. HEC has developed tools to serve these data even it the server is offline, but if you cannot access these data, expand the instructions below.
...we have provided the files you would download here.
Terrain Files.zip
Download them to your files folder.
Then, instead of choosing Download USGS terrain tiles directly choose Pick a raster file from the file system and import these files into the terrain.
There are several different resolutions and scopes of data in this location. Let's get the channel data first.
This river has Green LiDAR along the channel that we can import for our bathymetry.
Set the Filter to Original.
The channel data tiles align with the channel. You will need three of them.
Press the "Cloud/Download" button to download each of them.
Now let's get the floodplain and terrestrial data.
Set the Filter to 1 Meter and select the most recent (8/5/2025) 1X1 degree terrain.

There is a 1-meter coverage which is good resolution, but the areal extent is much larger than we need for this small model.
Press the "Cloud/Download" button to download it
While this is downloading, you can download the topo-bathymetry data.
Make sure all files are done downloading, then press Import
Click on Components in the right pane associated with the Terrains.
You downloaded 4 tiles, but two different types. HEC-RAS combines tiles of like source and resolution and calls each set "Merged"
Let's change the symbology to see the data better.
1. Switch to the Layer tab in the right pane
2. Press the pencil button next to the Terrain Symbology to expand the symbology options
3. Select the Update for View option. Zoom in or out and press the button again to get the symbology you want.
Switch back to the Components tab.
1. Try re-ordering your "Merged" terrain Files to make sure your channel data are on top.
2. Try Right Clicking on the Terrain File in the Model Tree and select Open Terrain Editor.
3. This will allow you to look at each terrain file individually. Try clicking on the two files in turn.
4. Click back to the Map tab at the top of the display to get back to the main display.
Draw a profile line to view the cross section
1. Expand the Features node.
2. Turn on the Profile Lines.
3. Select the Edit tool.
4. Draw a profile line across the channel.
5. Right click on the profile line.
6. Select Plot→ Terrain Profile

Profile line.mp4

Step 3: Add Channel Mods from 6.X

Channel modifications are high on the RAS2025 priority list, but they are not in RAS2025 yet.
You can make your channel modifications in HEC-RAS 6.X and import them.
This section will guide you through that process.

Open HEC-RAS version 6.7 (or 6.6).
Open the project file in the folder provided called HECRAS6Project and then open RAS Mapper.
Turn on the first Terrain file (called "Terrain") with the Modifications and Piers.
We are going to export just these pier mods as a terrain file you can add to your RAS2025 terrain
Make a new terrain.
1. Right Click on Terrains. (the parent node of all the terrains).
2. Select Create a new Terrain.
3. Press the folder button to give it a new name
  1. Name it "Only Piers"
4. Select Create Empty to make a terrain file with nothing in it.
Transfer the modifications
1. Right click on Modifications of the original terrain
2. Select Copy Modifications To..
3. Then select the new, empty terrain to transfer the modifications to it.
4. If you turn off everything except for the new terrain and modification you will see that you isolated the piers.
Export the piers and import them into
1. Right click on the terrain and select Generate New RAS Terrain
2. This will convert your "vector" modifications to a Raster, so export these modifications at a very small cell size, like 0.1 ft.
  You need a very small cell size to capture the appropriate resolution of vector pier mods, but if you do not isolate the piers, you will export everything at this resolution, which creates a very large file.
3. Import the Piers into RAS2025
  1. Drag the tiff you just made of the piers to the terrain
    Note: This is a big difference with terrains in RAS2025, you can add to them after you create them
  2. You can right click on the terrain and select Open Folder in File Explorer to find it.
    1. The file will have a complex name like Only Piers(1).Only Piers_0.1ft.tif.
    2. You can copy it and rename it to "Piers.tif" if you'd like
  3. Drag it onto the Blue dot
  4. Reorder your terrain components if you need to and verify that you brought in your pier.
    Import Pier.mp4

Step 3: Import Land Cover Data

There are advantages to already having a conceptual mesh when you define n-values (which we will focus on in most of the rest of the class).

But it is remarkably easy to copy a geometry with a mesh in RAS2025, so we will just copy into our project for now.

Copy a Geometry File

Select the File | Open Folder menu item
This will bring you to the project directory, which you will see already has folders for Geometries, Boundary Conditions, Terrains, Results and other files.
In this architecture, you only need to copy one of these files into one of these folders for HEC-RAS to fully recognize it.
Copy the geometry file provided (ExampleGeometry.H5 in the Geometry folder of your workshop files) into the Geometries folder of your project.
When you return to HEC-RAS you will see this geometry under the Geometries node on the tree. Turn on the new geometry and the Conceptual Mesh.

Import NLCD

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.
Import the NLCD land cover dataset.
1. Press the Import NLCD (2021) button.
2. Compare this land use to the imagery.
  1. Go to the globe icon in the upper right of the diplay.
  2. Turn on the Satellite Imagery
  3. Adjust the Opacity until you can make out the imagery and the land use together as an overlay

The NLCD data is a pretty rough estimate of land use. It may be appropriate for hydrologic scales, but you do want to verify it for a model of this scale, at least to understand the associations it is making before you assign n values.

"Open Water" Raster data is almost never sufficient to define your channel n-value. You will need to define your channel with vector data.

Fortunately, defining your channel is already best practice in a RAS2025 so you are likely to already have what you need already.

Step 4: Import Repaired Channel Data

Raster data is almost never sufficient to define 2D channel n-values.
As in HEC-RAS 6.x, you will need to add classification polygons to augment the land use raster classification.
But digitizing your channel in your conceptual mesh is best practice for most models in RAS025, so you already have channel shape files you can use (which is why we imported the conceptual mesh).

Copy a channel segment
1. Start Editing. Push the Edit pencil.
2. Click on the Conceptual Mesh node.
3. Right click on one of the channel polygons from the conceptual mesh.
4. Select Copy | Region Polygons and Region Metadata (Ctrl+C also works)
Paste the shape into your classification
1. Right Click on the Classification
2. Select Paste Features
3. Select Import in the preview window.
4. Click on Classification Polygons in the Components pane on the right.
5. The Polygon will appear under the Polygons list labeled No Data
  1. Change the label to "Channel"
  2. Repeat with the other Channel Regions, call them all Channel
6. Repeat for the other channel shapes
  1. These polygons will populate under the Classification Polygon
  2. You will have to click back on the Conceptual Mesh node to copy each one.

Step 5: Define n Values

The Classification is a generic association between spatial data and labels.
The n-Value layer associates n-values with those classifications, to map them spatially.
You will eventually be able to add other 2D Surface Layers (e.g. infiltration, bed gradation, etc) using the same classification or a new one.

Create an n Value Layer.
1. You can add an n-value layer by pressing the "+" on Surface Layer but there is an easier way.
2. In your classification, under the Components tab press the Create N-Value Layer from this.
3. Give it a name ("n Value" is fine).
Define n-Values
1. Click on your new n Value Layer
2. The components tab will populate the NLCD classifications with some first-order estimates of a starting Manning's Coefficient.
3. If you scroll down to the bottom, your "Channel" classification defaults to 0 because we created it and it doesn't have a default.
4. Set Channel to 0.045.
5. Then try updating one of the other types (e.g. change Pasture/Hay to 0.5) to explore the functionality.

Step 6: Adding Patched Channel Data

(If you have time)

The topobathymetric data collection had a depth limit, so it does not resolve deep pool data.

The water surface for the topographic data below the channel data will "show" through the hole in the channel data, essentially forming a pillar in the middle of your channel.

We patched the channel data in RAS 7.0, and we are going to bring that channel data in to our model.
Note: HEC is working on tools to automatically interpolate holes like this on import, but for now we need to patch them in 6.7.

Patch.mp4

Find the Terrain in your starting data files called PatchedChannel.tif (in the Channel Terrain folder)
Select your Terrain and make sure you are on the Components tab.
Drag the Patched Channel terrain onto the Layers area (or press the blue circle and navigate to it)
Press the Import button.
You will have to go to the Layer tab and Update for View again to get a useful color ramp.
It should be above the imported data but below the piers
Click on the new patched channel terrain and pull it down below the Pier terrain.

Workshop Solution: Terrain and LC WS Solution.zip