RDII Hydrographs

Create or edit RDII Unit Hydrograph objects.

Unit Hydrographs (UHs) estimate rainfall-derived inflow/infiltration (RDII) into a sewer system. A UH set contains up to three such hydrographs, one for a short-term response, one for an intermediate-term response, and one for a long-term response.

A UH group can have up to 12 UH sets, one for each month of the year. Each UH group is considered as a separate object by SWMM, and is assigned its own unique name along with the name of the rain gauge that supplies rainfall data to it.

Each unit hydrograph is defined by six parameters:

• R - The fraction of rainfall volume that enters the sewer system.

• T - The time from the onset of rainfall to the peak of the UH in hours.

• K - The ratio of time to recession of the UH to the time to peak.

• DMax - The maximum initial abstraction depth available in mm.

• Drec - The initial abstraction recovery rate in mm/day.

• Do - The initial abstraction depth filled at the start in mm.

Procedure

1. The RDII Unit Hydrograph Editor displays.

2. You can only edit the unit hydrograph once you have selected an associated rain gauge.

See Also Inflows