Rainwater options (Wastewater options wizard)

In the Rainwater options area, properties for determining the rainfall donations and runoff coefficients for determining the rainwater runoff are defined.

Determination of the rainfall contribution

  • If the From KOSTRA-DWD grid data checkbox is activated, the rainfall data from the German Weather Service (DWD) is used for rainwater drainage and additional emergency drainage (KOSTRA-DWD: Coordinated heavy precipitation regionalisation and evaluation of the DWD).
    Note:
    To use the data from the German Weather Service, a postcode must be specified in the project cover sheet.

    If the From KOSTRA-DWD grid data checkbox is deactivated, you can specify the rainfall amounts in l/(s*ha) manually.

  • Use the Safety surcharge according to KOSTRA-DWD checkbox to define whether a percentage safety surcharge is to be applied to the rainfall amounts depending on the return period.
    Note:
    If the design is based on a return period of 2 or 5 years, a safety margin of 10 % is applied. If you have selected a return period of 30 years, a safety margin of 15 % is applied. For a return period of 100 years, a safety margin of 20 % is taken into account.
  • In the Return period drop-down menu, select the frequency of the rain event in years.
  • The rainfall duration shows the duration of the rainfall event in minutes.
    Note:
    For roof drainage areas in accordance with DIN 1986-100, Table A.1, 5 minutes is always used as the rain duration.
  • If an exceptional level of protection is required for a building (see DIN EN 12056-3, Table 2), the entire century event should be drained via the emergency drainage system in accordance with DIN 1986-100. In this case, the Emergency drainage exceptional level of protection checkbox must be activated.

    If the Emergency drainage exceptional level of protection check box is deactivated, the event of the century is drained via the difference between the calculated rainfall and the emergency drainage.

  • In the Reservoir height area, enter the maximum reservoir height in mm on the roof.

Discharge coefficients Cs for determining the rainwater runoff