Inundation in Germany due to heavy rain

Heavy rain events with flooding in May and June 2016

In May and June 2016, heavy flooding resulting from exceptional precipitation occurred in Germany. The small townships Braunsbach (Baden-Württemberg) and Simbach am Inn (Bavaria) attracted special attention in the media due to the extent of inundation and damage. During summer 2016, the Bavarian State Office for the Environment registered more than 50 flood events due to severe rain. Despite their small spatial extent, these extreme events caused devastating damage and even casualties.

Picture: marlene Thyssen

Heavy rain events: small-scale and highly variable

As a rule, heavy rain events are small-scale and temporally very dynamic. Within a very short time, a large amount of rain falls, which can no longer infiltrate into the soil and is available to become surface runoff. Especially in small catchment areas, very fast torrential flood waves can arise from this.

Pictures: Harald Weber, Hans Stüben

Expected increase of severe rainfall events

Because of climate change, Central Europe has to expect an increase of extreme rainfall events. Thunderstorms and heavy precipitation cells are likely to occur more frequently especially during the summer period. Consequently, the preparation for flood events due to heavy rain gains additional importance.

Objective of the HiOS project

The events of 2016 have shown that prevention against floods caused by severe rain events has to be improved. In contrast to a large-scale and long-lasting river basin floods, these inundations develop on areas even without any relation to water courses and generate flash floods along small waterways. This requires a new approach. The HiOS project investigates possibilities for the efficient and reliable modeling of such events. In addition, a map for Bavaria will be prepared, which gives first indications for areas with increased hazard probability due to surface water and flash flood. This guidance map can be a basis and decision-making aid for more detailed investigations and other precautionary measures.