海角视频

Between 2002 and 2021, heavy rainfall events in Germany caused damages amounting to . In 2024 alone, insured losses from extreme weather 鈥� including heavy rain, flooding, storms and hail 鈥� totalled .

The increase in extreme weather events, in particular, heavy rainfall poses major challenges for cities and municipalities. These events are characterised by intense precipitation, often limited in area but with the power to cause enormous damage.

The consequences are overloaded sewer systems, flooded streets, damaged infrastructure and buildings, and water pollution. Climate researchers expect such events to become even more frequent in the future 鈥� municipalities are therefore required to adapt their infrastructure to this new reality.

Where are cities most vulnerable?

Densely populated cities with a high proportion of sealed surfaces or those located on slopes are particularly at risk of dangerous flash floods. In flatter urban areas, sudden volumes of water can overwhelm sewers and local watercourses, flooding large areas. Heavy rainfall hits cities hard when infrastructure is not designed for large quantities of water.

Weak points are:

• Low-lying districts and underpasses that collect water
• Sealed surfaces such as car parks, driveways, streets and courtyards that cannot absorb water
• Old sewer networks not built for today’s rainfall volumes
• Lack of retention areas to slow down water discharge
• Inadequate early warning systems preventing timely response
• Lack of awareness among stakeholders

An important source of information for local risk assessment is heavy rainfall hazard maps, which illustrate flood depths for different rainfall scenarios. Thanks to funding, these maps are now available in many municipalities and inform both local authorities and residents. A good example of such a map is the of the city of Frankfurt am Main, which not only shows the flooding depth but also flow velocity.

Measures for heavy rainfall resilience

The German Environment Agency, the , estimates the risk of heavy rainfall to be equally high everywhere in Germany. Even regions without previous experience of such events should be aware of the dangers. However, flooded streets, basements and overloaded sewer networks prove that many cities are not prepared for these volumes of water. Effective heavy rainfall prevention requires a mix of organisational and structural measures, coordinated to close gaps and mitigate risks. When implementing decentralised measures, impacts on neighbouring areas should always be considered to avoid simply shifting problems.

Planning and organisational measures

• Create hazard maps and risk analyses to identify flood zones and runoff paths
• Integrate sponge city principles early in district development
• Include rainwater management in land-use and development plans
• Establish early warning systems and information platforms
• Network urban planning, landscape planning, environmental agencies and water management
• Advise and raise awareness among property owners
• Set up municipal funding programmes to support decentralised measures

Structural measures

• Unseal surfaces such as car parks, driveways and courtyards for rainwater retention
• Incorporate retention roofs
• Create multifunctional open spaces based on sponge city principles that can absorb water during heavy rainfall, e.g. sports fields or schoolyards
• Allow rainwater to infiltrate and evaporate locally via swales or infiltration trenches
• Store and treat rainwater for use as greywater in building or for irrigation

A key strategy for adapting to heavy rainfall is the sponge city principle. It describes cities that function like a sponge: rainwater is not immediately discharged but absorbed locally, stored and slowly released. The aim is to relieve sewer systems and prevent flooding. Measures such as green roofs, retention areas, infiltration swales and unsealed surfaces are typical elements of this strategy. They not only improve water management but also enhance the microclimate during heatwaves and thus the quality of urban spaces.

Such measures, which use natural processes to mitigate heavy rainfall risks, are also referred to as nature-based solutions. They offer ecological, economic, social and cultural benefits and address multiple challenges simultaneously.

Adapting to increasingly frequent heavy rainfall events poses major challenges for all stakeholders. Municipalities often lack financial resources and personnel to advance resilience. A key starting point for continuous implementation is a concept that lists coordinated measures. Even if not everything can be implemented immediately, it provides structure and clarity. Risk hotspots can be identified and addressed, and measures can be planned when areas are being redeveloped anyway, or new funding opportunities arise. Such opportunities occur, for example, when municipal buildings are renovated or roads need to be renewed.

From planning to implementation

Resilience begins with planning. Rainwater management experts should be involved as early as the development plan stage. This allows capacities to be calculated and measures defined early on.

Structured concepts – A well-thought-out concept forms the basis for systematically strengthening resilience against heavy rainfall. It identifies vulnerable locations, prioritises measures and gives prevention a clear structure.

Success through collaboration – Urban planning, landscape planning, environmental agencies and water management must work closely together 鈥� even across property and municipal boundaries. Only then do systemic solutions emerge.

Communication and advice – Targeted engagement with property owners is essential. Hazard maps can help illustrate risks 鈥� even if they encounter resistance due to potential value losses or higher insurance premiums.

Best practice examples

Spreepark, Berlin – An innovative rainwater management system was integrated into the redevelopment of Spreepark, a former amusement park. The first of three planned cisterns has already been installed 鈥� with a capacity of 150m鲁. It collects rainwater from the workshop roof and provides it for park irrigation. The cistern was assembled modularly in the excavation pit, allowing flexible adaptation to local conditions. This project shows how technical solutions can be combined with ecological and design requirements. Further cisterns are planned to sustainably manage the entire site.

52掳 Grad Nord, Berlin – This new quarter in Berlin-Adlershof is a flagship project for implementing the sponge city principle. In the first construction phase, a 6,000m虏 water basin was created, fed by rainwater from surrounding buildings. The houses have green roofs that retain and evaporate water. Additionally, rainwater is returned to the natural cycle via swales and underground infiltration trenches. Sand traps clean the water before infiltration. The project received the 鈥淩egenial鈥� award from the Berlin Rainwater Agency.

Neues Gartenfeld, Berlin – This project transforms a former industrial site into a sustainable urban district. On 36 hectares, a 鈥渮ero-discharge settlement鈥� is being created, where all rainwater is used and stored on site. A central rainwater basin serves as a retention area and leisure space. The system is complemented by retention roofs, treatment facilities and intelligent storage management. A dedicated greywater plant supplies the district with treated rainwater. Planning takes into account complex challenges such as contaminated soil, high groundwater levels and drinking water protection zones 鈥� an example of holistic infrastructure planning.

Key learnings

Heavy rainfall events are no longer rare occurrences – they represent a growing challenge for urban environments. Cities must adopt proactive strategies to mitigate risks and protect communities. The key learnings highlight that resilience starts with structured concepts, enabling prioritisation and clear planning. Early integration of rainwater management into urban development is essential, while nature-based solutions offer cost-effective, multifunctional benefits. Combining centralised and decentralised measures, fostering cross-sector collaboration, and maintaining transparent communication with stakeholders will ensure systemic solutions that enhance both climate adaptation and urban quality of life. By embracing these principles, municipalities can futureproof their cities against the increasing threat of heavy rainfall.