Subbasins define the drainage area polygons that produce runoff to other elements in the model. GeoHECHMS software automatically calculates and assigns the drainage area for the subbasins from the defined subbasin polygon. The user can keep using the polygons or revise the polygons to represent the actual shape of the drainage area. If the user revises the subbasin polygons, then the drainage area value can be recalculated for the corresponding subbasins using the Compute Subbasins Areas command. This command allows the user to compute the drainage area of multiple subbasins simultaneously.
Follow the steps below to use the Compute Subbasin Areas command:
- From the Input ribbon menu, select the Drainage Subbasins menu item and select the Compute Subbasin Areas command.
- The Compute Subbasin Areas dialog box will be displayed.
- Select the subbasins for which the drainage area needs to be calculated.
- Alternatively, click the [Pick] button to select the subbasins from the Map View interactively. On clicking the [Pick] button, the Compute Subbasin Areas dialog box will temporarily disappear, and a prompt will be displayed on the status bar directing the user to select the subbasins. Select the subbasins from the Map View. Once finished, press the [Enter] key or right-click and select Done from the displayed context menu. The dialog box will be redisplayed. The number of selected subbasins will be displayed in the Total selected read-only field.
- Once the subbasins are selected, click the [Compute] button. The software will compute the drainage area for the selected subbasins and update their drainage area values.