This dialog allows for editing of a Global Database record for the Unit Hydrograph (UH) method for modeling Rainfall Derived Inflow and Infiltration (RDII) in combined sewers. This method is also referred to as the RTK method. It is selected in the Sub-Catchment dialog in Runoff Mode.



The options for months are:

  • A default UH for All Months 
  • Separate UH for any month

If a month is not checked, the All Months UH Method will be used during the simulation in that month.

For each of the three component UHs enter:

  • fraction of total rainfall entering the system (R)
  • time from the beginning of the rainfall to the hydrograph peak, hr (T)
  • ratio of time of recession to time to peak (K)
  • initial subcatchment abstractions, in (mm)
  • initial subcatchment storage, in (mm)
  • recovery rate of storage (initial abstractions) during dry time steps, in/day (mm/day)

In the drop list next to rainfall select a rainfall record from the Global Database.