Floods; determination of floodplains

The most effective way to avoid flood damage is to prevent potential damage in areas at risk of flooding from occurring in the first place. The Water Resources Act obliges the federal states to designate at least those areas within risk areas or assigned areas where a flood event is statistically to be expected once every 100 years and the areas required for flood relief and retention as floodplains.

In Bavaria, there is a need to identify floodplains along all major watercourses, the first and second order watercourses with a total length of 9,000 km, and above all in settlement areas along the smaller watercourses, the third order watercourses. These areas are defined by legal ordinance of the district administrative authority.

A digital terrain model, survey data and the evaluation of land use data and aerial photographs form the technical basis. This allows a flood event to be simulated, which statistically occurs once every 100 years, and the corresponding floodplain to be determined.

The water management authorities pass these results on to the district authorities for approval in the form of site plans.

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

Further specific prohibitions apply to designated flood areas. These include, for example, raising and building on a property and storing objects that could obstruct the flow of floodwater or be swept 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 inventory against flooding and rising groundwater (see "Related links").

There are discharge gauges on the Regnitz and Schwabach rivers in the city area where the water level is regularly measured and documented. The current water levels and characteristic discharge data for the Regnitz and Schwabach are published by the Bavarian State Office for Water Management (see "Related links").

Which areas in the city of Erlangen are at risk of flooding can be viewed in the Bavarian Environmental Atlas or in the BayernAtlas (under "Change topic" - "Natural hazards" - "Floods").