Creating catchments in Civil 3D

Step-by-step 

In Civil 3D, after the drawing has been set up for InfoDrainage and the manholes and pipes have been inserted, the catchment areas need to be created. Each catchment object is comprised of a boundary and a flow path.

Catchments can be created from the surface, or as is the case in this exercise, from objects by copying and pasting polygon objects onto the existing surface.

1. Open the file pipesandmanholes.dwg.
2. Open the file Catchments.dwg. These seven polygons represent seven subcatchment objects.
3. Highlight all the subcatchments.

4. Copy them to the clipboard.
5. Use PASTEORIG to paste the subcatchments into the current surface drawing, pipesandmanholes.dwg. (The PASTEORIG command allows for the origin to align so that the pipes are placed correctly.)

To designate these polygons as catchments in Civil 3D:

6. On the ribbon, Analyze tab, Ground Data panel, expand Catchments.
7. For this exercise, select Create Catchment from Object since the subcatchment areas have already been created.

8. At the prompt, “Select polyline for catchment area boundary”, place your cursor over the first polygon.

9. After the first polygon highlights, click to select it.
10. At the prompt, “Select a polyline on the uphill end to use as a flow path (or press ESC to skip)”, press ESC. (A flow path can be created in InfoDrainage.)

The Create Catchment from Object dialog box appears. Here, designate the manhole for the new catchment object by adding the reference pipe network structure. Note that this step can also be performed in InfoDrainage. To do so here:

11. Click Select reference structure:

12. At the prompt to select a pipe network structure, in the drawing, select Structure – (1).

13. Back in the Create Catchment from Object dialog box, about halfway down, click the Catchment tab.
14. Set the Catchment style to Standard.
15. Set the Catchment label style to Name Only.
16. Set the Flow segment label style to None.
17. Click the Flow Path tab.
18. Expand the Calculation method drop-down and select TR-55.

Note: InfoDrainage has more detailed tools for flow paths, so the defaults can be accepted here in Civil 3D.

19. Click OK.

Notice that the highlight color for the subcatchment changes to show that the manhole has been assigned.
Also, the Command line reports the calculated 2D area of the new catchment:

20. Repeat steps 11 - 19 for the remaining catchment areas.

IMPORTANT: Reference each catchment area to the correct structure.

21. Save the file as “Withcatchments.dwg”.