Flood risk in Germany - How to protect municipalities and the population

In the summer, extreme heavy rainfall has caused flooding and massive destruction in municipalities and districts. The statistics show that in the future we will have to deal with such extreme weather events and their consequences more often in Germany. What can be done? The IOER has been researching this question for many years and developing solution strategies with partners from science and practice.

The devastating consequences of the flood disaster in July in parts of North Rhine-Westphalia and Rhineland-Palatinate have left many people speechless and shocked. It almost seems as if people are unprotected against the forces of nature. However, research on the topic of environmental hazards and their consequences for landscapes, cities, neighbourhoods and buildings has long been available. For many years, the Leibniz Institute of Ecological Urban and Regional Development (IOER) and its partners from science and practice have been investigating how cities and regions can better adapt to extreme weather events such as heavy rainfall. Numerous approaches, planning instruments and entire "toolboxes" are available for districts and municipalities, architectural and planning offices as well as citizens.

At a glance: projects, approaches, instruments and tools

RAINMAN - Integrated heavy rain risk management
Flooding and damage can also affect places that are not located on large rivers or other waterbodies. The reason: extreme heavy rainfalls can occur anywhere. It is very difficult to estimate exactly when and where; usually there is hardly any time to warn in advance. Assessing possible risks from heavy rainfall in advance and taking appropriate measures to minimise potential damage is therefore even more important. The EU project RAINMAN has investigated what these measures might be. The project partners have developed a set of innovative methods and tools for integrated heavy rainfall risk management in Central Europe and tested the instruments in various pilot regions. The RAINMAN-Toolbox provides municipalities and interested parties with this collection of information, tools and practical examples for dealing with the natural hazard of heavy rainfall.

STRIMA I + II - Saxon-Czech Flood Risk Management
Floods do not stop at national borders. This makes cross-border cooperation all the more important in the event of a crisis, but also in risk prevention. The STRIMA I and II projects aimed to promote cooperation in flood risk management between Saxony and the Czech Republic. In addition, the project partners developed FLOOD.Bi, an information tool for buildings on the topic of flooding and damage reduction. It helps to minimise the risk of flood damage to buildings through forward-looking planning and structural adjustments. FLOOD.Bi is available to building owners as well as to professional planners and engineering offices.

Flood Protection Guide of the Federal Government
Evade, resist, adapt - there are different ways of adapting buildings to the new challenges posed by weather extremes. Experts distinguish between three basic concepts for flood-resistant construction and redevelopment of buildings. The concept of "evasion" is the most effective in reducing flood damage. Among other things, evasion includes not building in flood-prone areas as a matter of principle. The concept of "resistance" aims to prevent floodwater from entering the building, for example through structural measures. The concept of "adaptation" does not work against the flood, but allows buildings to be flooded systematically. All three concepts require good planning and appropriate structural adaptation of buildings. The scientists of the IOER have prepared their advice in detail for the Flood Protection Guide of the Federal Ministry of the Interior, Building and Community (BMI). This and other important information can be found there.

HUeBro - Elevated housing in areas prone to flooding using the Elbe village of Brockwitz as an example
Necessity is the mother of invention – this saying also applies to flood prevention. In the Saxon village of Brockwitz located near the Elbe river, science and practice are breaking new ground. Parts of the village with a 1,000-year history have been flooded several times since 2002. One promising option to protect houses from flooding is to elevate them. However, how can buildings under preservation orders be raised, what does it cost and what are the consequences for the historic townscape, nature and landscape? A feasibility study has worked out answers to these questions - and it has convinced: the project in Brockwitz is to be implemented as a model project in the coming years. The German Bundestag has approved funds for it. Other municipalities could learn from it.

Retreat of settlement areas as part of risk prevention - practical aid for municipalities
After the clean-up, the question is: Rebuild or retreat? Sometimes the most sensible thing to do is to give in and retreat - this is also true when it comes to flooding. If extreme events such as heavy rainfall and flooding are to be expected more frequently in the future, then it is advisable not to build in particularly endangered areas and even to abandon existing settlements. Risk prevention and the protection of human life and economic values then have priority. In politics and the public, such a retreat of settlement areas is predominantly perceived negatively. But there are also advantages. A practical guide on the topic shows which advantages these can be and how municipalities can discuss the advantages and disadvantages of a partial adaptation of their settlement structures in an open dialogue. The Federal Environment Agency (UBA) published it in June 2021. Researchers from the IOER have contributed important aspects on the topic.

Scientific contact
Dr.-Ing. Regine Ortlepp (RAINMAN), e-Mail: R.Ortleppioer@ioer.de
Dr.-Ing. Reinhard Schinke (STRIMA/FLOOD.Bi), e-Mail: R.Schinkeioer@ioer.de
Dr. Marco Neubert (elevated housing Brockwitz), e-Mail: M.Neubertioer@ioer.de
Prof. Dr. Gerold Janssen (practical guide on retreat of settlement areas), e-Mail: G.Janssenioer@ioer.de

The Leibniz Institute of Ecological Urban and Regional Development is jointly funded by the federal government and the federal states.

FS Sachsen

This measure is co-financed by tax funds on the basis of the budget approved by the Saxon State Parliament.