- How Hesse's municipalities are preparing for heavy rains
Heavy rain is one of the most dangerous weather events, as recently seen in North Hesse. In a short amount of time, immense rainfall occurs, leading to flash floods that inundate streets and homes, and even sweep away cars. Such storms cannot be prevented, but with advanced technology, efforts are made to gain a head start to warn all involved and save lives.
County Fulda is relying on smart technologies in its fight against heavy rain. Since May, the county administration reports that the step-by-step built-up early warning system for heavy rain is in operation in all 23 communities.
200 sensors installed
For this purpose, around 200 sensors have been installed in sewers, at bridges, public buildings, and waterways. The measuring devices determine rainfall amounts and water levels and analyze the flow behavior in channels. In real-time, the data is played into a cloud and compared with current measurements and weather forecasts from the German Weather Service (DWD).
Artificial Intelligence is also used in the evaluation of the data, as explained by the Hessian Ministry of Digital. "The measurement results are automatically analyzed to optimize the alarm process in a self-learning manner."
Warning in seconds
When it gets critical, the early warning system triggers an alarm in the population, with rescue services and the administration in seconds. The warning is transmitted via SMS, email, or voice call. "For this, it is only necessary to download a free app," explains a spokeswoman for the county.
The key to the system is the speed with which a danger is recognized and the corresponding warning is spread. "This time advantage is enormously important and a great benefit," emphasizes the spokeswoman. "Citizens have the opportunity to clear their basements in time or, in extreme cases, leave their homes." Fire departments could also be informed in advance about water levels and potential flash floods and, if necessary, build barriers.
Model to be transferred to other counties
The early warning system was funded by the Ministry of Digital with around 830,000 euros from the "Strong Home Hessen" program. According to the ministry, the model is also to be transferred to other counties in Hesse.
Another project of the county in this context is the establishment of the homepage starkregen-fulda.de. Via this portal, citizens have the opportunity to record and share experiences with past heavy rain events and their consequences.
This includes clogged sewers, blocked outlets, overloaded ditches, and bottlenecks in waterways. After filling out a corresponding profile of the observed danger, the data is checked by the Lower Water Protection Authority in coordination with the respective municipality and finally released.
Other municipalities also prepare
Other Hessian cities such as Frankfurt, Darmstadt, and Limburg have also been preparing for heavy rain for years with different measures. This includes the creation of danger maps on which flood depths and flow speeds can be read for the respective urban area.
In Frankfurt, a map like this already exists, while in Darmstadt and Limburg it is still being developed. This map will serve as a basis for future adaptation measures by the city and private individuals, as stated in Darmstadt. This includes the unsealing of surfaces, decentralized rainwater retention measures, or suitable street and green space design. These and other measures will be visible in the Darmstadter Climate Adaptation Plan, which is currently being developed and is expected to be published in the first quarter of 2025.
Furthermore, private individuals will be informed about how to implement flood prevention measures on their own property and may receive financial support, for example through the city's funding program for cisterns and greywater systems.
Risks vary depending on geographical location and building structure
The potential hazards in the individual municipalities depend on their geographical location and building structure - for example, the region of Limburg with its slopes above settlement areas generally has a higher risk potential than areas with flat terrain, as stated by the city. In addition, natural drainage paths from slopes are often interrupted or extremely narrowed by construction. Just a few weeks ago, water from heavy rain entered houses in the Limburger district of Dietkirchen that are directly adjacent to agricultural land.
Protection against heavy rain hazards is already included in urban planning
In many places, protection against heavy rain is already integrated into urban planning and land-use planning - for example, in Frankfurt with measures to deal with rainwater in the Riedberg district. In land-use planning, attention has been paid to local infiltration and evaporation for many years, for example through green roofs and walls and low surface sealing. Darmstadt also aims for sparse sealing and low land consumption, with more green spaces and unsealed areas. Accordingly, the building plans usually contain corresponding regulations.
Limburg, according to the city's statements, implements the concept of the sponge city in current building plans with green roofs, lower sealing degrees, and the creation of depressions on private properties to retain rainwater. However, since the capacities for the water volumes are not sufficient, as recent experiences have shown, it is necessary to also consider agricultural land and prevent "long periods of bare soil", explained the city.
The municipality of County Fulda is utilizing advanced technologies to combat heavy rain, with the assistance of a government grant. Following the implementation of an early warning system, 200 sensors have been installed across various locations to monitor rainfall, water levels, and flow behavior.
In light of the increasing threats posed by heavy rain events, other municipalities in Hesse, such as Frankfurt and Darmstadt, have also begun preparing by creating danger maps and integrating flood prevention measures into their urban planning and land-use strategies.
