The flood waves from the recent floods in Central and Eastern Europe are now reaching Germany. For developers of energy projects to assess the risks of potential flooding early, they should examine flood zones and flood risk maps. According to Section 78 of the Water Resources Act (Wasserhaushaltsgesetz), "the designation of new building areas in external areas in development plans" or "installations according to Sections [...] 35 of the Building Code" (privileged installations) are prohibited in designated flood zones.
Interestingly, in 2023, the Federal Council, at the initiative of Bavaria, introduced a draft law that would have legally privileged the construction of PV systems in flood zones, making them permissible within these areas. The justification was that neither the soil is sealed, nor is the flow of floodwater affected. However, the Bundestag rejected the proposal in light of the significant damage caused by past flood disasters.
The identification of legally valid flood zones is thus crucial for project developers, although it is not always straightforward. For example, in Schleswig-Holstein, there are flood zones that are either "designated," "provisionally secured," or "legally defined." In Saxony, a distinction is made between "designated" flood zones and "flood-prone" areas. In Baden-Württemberg, there are "HQ100" zones and "flood zones," which are further divided into "designated by regulation," "published by public display," and "HQ100 zones outside HWGK" (flood risk map).
These categorizations usually only indicate the legal basis for designating an area as a flood zone. In Saxony, however, construction restrictions do not apply to all "flood-prone" areas but only to those where a flood event is statistically expected every 100 years.
This is an important point, as Section 76 of the Water Resources Act (WHG) stipulates that all flood risk areas with a 100-year event probability (HQ100) must be designated as flood zones by the state governments. Unfortunately, these zones are not always found in flood zone data, in addition to inconsistent categorization.
Therefore, it is important to consider not only flood zones but also flood risk areas during project development. This is especially true since insurers also examine these areas.
Project developers can view all flood and flood risk zones in the dvlp.energy app. Due to frequent data updates, the app always reflects the latest status of both types of areas. Currently, the preliminary reassessment of flood risk areas is underway, which must be reflected in official flood hazard and risk maps by the end of 2025. According to Section 76 of the Water Resources Act, this will then directly lead to the designation of flood zones.
