Flooding; Designation of Floodplains

The most effective way to prevent flood damage is to take preventive measures to ensure that potential for damage does not arise in the first place in areas at risk of flooding. The Water Resources Act requires the federal states to designate as floodplains, within risk areas or designated zones, at least those areas where a flood event is statistically expected once every 100 years, as well as areas used for flood discharge and retention.

In Bavaria, there is a need to identify floodplains along all major watercourses—first- and second-order watercourses with a total length of 9,000 km—as well as, particularly in residential areas along smaller watercourses (third-order watercourses). These areas are designated by statutory order of the district administrative authority.

Technically, a digital terrain model, surveying data, and the analysis of land-use data and aerial photographs form the basis. This allows for the simulation of a flood event that statistically occurs once every 100 years and the determination of the corresponding floodplain area. 

The water management offices submit these results to the district administrative authorities in the form of site plans for designation.

Various prohibitions apply in designated floodplains. For example, no new development areas may be designated in urban land-use plans or other statutes under the Building Code within designated floodplains. Exceptions are only possible under strict legal conditions.

Additional specific prohibitions apply to designated floodplains. These include, for example, raising the elevation of a property or constructing buildings on it, as well as storing items that could obstruct floodwater flow or be washed away. For existing buildings in flood-prone areas, the Federal Ministry of Transport, Building, and Housing provides tips in a flood protection guide on how to protect buildings and their contents against flooding and rising groundwater (see “Further Links”).

Along the Regnitz and Schwabach rivers within the city limits, there are discharge gauges where water levels are regularly measured and documented. The Bavarian State Office for Water Management publishes current water levels and characteristic discharge data for the Regnitz and Schwabach rivers (see “Further Links”).

You can view which areas in the city of Erlangen are located in flood-prone zones in the Bavarian Environmental Atlas or in the BayernAtlas (under “Change Topic” – “Natural Hazards” – “Flooding”).