Construction ban in flooded areas — but finding this is not always easy

The tidal wave of floods in Central and Eastern Europe is reaching Germany these days. So that developers of energy projects can assess the risks of potential flooding at an early stage, they should check flood areas and flood hazard maps. Because Section 78 of the Water Resources Act states that”the designation of new outdoor building areas in construction plans“or”Annexes in accordance with Sections [..] 35 of the Building Code“(privileged facilities) are prohibited in defined flood areas.

Interestingly enough, in 2023, on the initiative of Bavaria, the Federal Council introduced a bill that would have privileged the construction of PV systems under water law and would therefore have made it possible within flood areas. The reason was that neither the soil is sealed nor the runoff is affected by floods. However, the Bundestag rejected the draft in view of the major damage caused by past flood disasters.

Identifying the legally binding flood areas is therefore crucial for project developers, but it is not always easy. In Schleswig-Holstein, for example, there are flood areas that are “fixed”, “provisionally secured” or “legally defined.” In Saxony, a distinction is made between “fixed” areas subject to flooding and “flood-prone” areas. In Baden-Württemberg, there are “HQ100” areas and “flood areas”, which in turn are divided into “established by ordinance”, “published by interpretation” and “HQ100 areas outside HWGK.”

In most cases, the categorizations only indicate the legal background for the designation as a flood area. In Saxony, however, the structural restrictions do not apply to all “flood-prone” areas, but only to those that, statistically, fear a flood event every 100 years.

This is a good clue, because Section 76 of the Water Resources Act (WHG) states that all flood risk areas with an event every 100 years (HQ100) are to be designated as flood areas by state governments. Unfortunately, in addition to the inconsistent categorization, these areas are not always included in the data on flood areas.

It is therefore important to consider not only flood risk areas but also flood risk areas when developing projects. Not least because insurers are also examining these areas.

Project developers can view all flood and flood risk areas in the DVLP.energy app. Due to frequent data updates, the latest state of the area types is always shown there. In fact, the preliminary reassessment of flood risk areas is currently underway, which must be included in the official flood hazard and risk maps by the end of 2025 and, in accordance with Section 76 of the Water Resources Act, will then proceed directly to the designation of flood areas.