Now that we have a project setup and a projection defined, we can import the terrain. It is recommended that you clip the terrain raster to a buffer of the basin boundary. I used a buffer of 1km because if any part of 2D mesh extends beyond the terrain, the model will not run. I used Extract by Mask in ArcPro to clip the terrain raster.
In RAS Mapper, right click on Terrain and select Create a new RAS Terrain. Point to the clipped terrain and hit Create. RAS may take some time to import the terrain, depending on its size and resolution.
Once the terrain has been successfully imported, you can explore it in RAS Mapper. Turning on the Update Legend with View property makes it easier to see the changes in elevation.
Add a New Geometry
Next, we will create the geometry file that will be used to develop the 2D mesh. Right click on Geometries and select Create New Geometry. Give it a descriptive name. I have named this Geometry 2018ExistingConditions since that is when the LiDAR was developed. Under Geometries, you can see all the available components that can be used to develop the model geometry. We will go over these eventually. For now, save the empty geometry.
Manage Geometry Associations
We need to tell RAS to apply the Terrain to the geometry that we created. This is important when we have multiple geometries or multiple terrains that we are testing. Right click on Geometries and select Manage Geometry Associations. Ensure that the Terrain is matched with the geometry. You can see that there are other layers that are currently missing. They are not required to run a 2D model but may help to make the model more accurate
Now that we have a terrain, the next step is to create the 2D mesh.
Mapping T&T 