Sewer Network Capacity Analysis Part 3

This post follows on from the previous one on Creating Pipe Networks.

Creating Catchments
Before we export our pipe network to SSA for analysis we need to define our catchments.

You can do this by first creating polylines to define each catchment. Follow the approach outlined in the previous post of using the surface slope arrows and the kerb lines to determine what sections of surface drain to each structure. Once you have polylines drawn you can turn them into catchments

In the Prospector tab of Toolspace right click on Catchments and select Create Catchment Group. Then right click on the catchment group and select Create Catchment from Object. Select a polyline and press enter to skip the flow path option. In the dialog box that follows we need to set four things:

1. The catchment name - call this the same as the structure the catchment will flow to.
2. The reference structure - use the box to the right to select structure from the drawing.
3. The runoff coefficient - depends on the type of ground and will differ for the region or standard you are designing for but generally 0.9 for hard surfaces.

4. The Time of Concentration - On the Flow Path tab set the Calculation Method to User Defined. The TR55 option is a US based hydrology and doesn't apply here. The time will vary for the type of job you are working on but for a site like this 5 minutes would be sufficient. Enter the time in fraction of an hour - 0.083.

Repeat these steps for each catchment and you are then ready to export to SSA.

 

Export Pipe Network

On the Analyze tab of the ribbon select Edit in Storm & Sanitary Analysis

Select the pipe network and Ok. This will export to and open SSA.