Rainfall Intensity

DIN 1986-100 Annex A1 Determination of rainfall intensities (extract)
DIN 1986-100 Annex A1 Determination of rainfall intensities (extract)

The design rainfall intensities used during planning have a major influence on the drainage calculation for roof drainage, since they are needed to determine the required flow rate of the roof drainage in litres per second.

Rainfall intensity data is available free of charge at https://www.openko.de/.

What is rainfall intensity?

The local rainfall intensities are applied in the drainage calculation in accordance with the standard in order to determine the required flow rate of the roof drainage in litres per second. The "normal" rainfall intensity is used for the main drainage and the "once-in-a-century" rainfall intensity for the emergency drainage.

Because short but intense heavy-rainfall events are occurring more frequently, safety measures are increasingly being applied.

Rainfall intensity per postcode

The local design rainfall intensities are published by the German Weather Service (DWD) for each postcode under the name KOSTRA (Koordinierte Starkniederschlags-Regionalisierungs Auswertungen), based on "analyses of historical rainfall events and statistical calculations".

This regional analysis is the reason for the wide range of different local rainfall intensities across Germany, depending on the postcode.