- How Hesse's municipalities are preparing for heavy rains
Heavy rainfall is one of the most catastrophic weather events, as recently demonstrated in North Hesse. In a short period, vast amounts of rain fall, leading to flash floods that inundate streets and homes, and even sweep away cars. Such storms cannot be prevented, but with state-of-the-art technology, efforts are made to gain time to warn all involved and save lives.
The district of Fulda is using smart technologies in its fight against heavy rainfall. Since May, the early warning system for heavy rainfall, which has been gradually built up in recent years, has been in operation in all 23 municipalities in the district.
200 sensors installed
Around 200 sensors have been installed in sewers, at bridges, public buildings, and waterways. These sensors measure rainfall amounts and water levels, and analyze the flow behavior in channels. The data is played into the cloud in real-time and compared with current measurements and weather forecasts from the German Weather Service (DWD).
Artificial Intelligence is also used in the analysis of data, as explained by the Hessian Ministry of Digital Affairs. "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, rescue services, and 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 spokesperson for the district.
The decisive factor in the system is the speed with which a danger is recognized and the corresponding warning is spread. "This time advantage is enormous and a significant benefit," emphasizes the spokesperson. "Citizens have the opportunity to clear their basements in time or, in extreme cases, leave their homes." Firefighters could also be informed in advance about water levels and potential flash floods and, if necessary, build barriers.
Model to be transferred to other districts
The early warning system was funded by the Ministry of Digital Affairs with around 830,000 euros from the "Strong Hesse" program. The model is to be transferred to other districts in Hesse, according to the ministry.
Another project of the district in this context is the establishment of the homepage starkregen-fulda.de. Citizens have the opportunity to enter and share their experiences with past heavy rainfall events and their consequences via this portal.
This includes, for example, clogged sewers, blocked culverts, overloaded ditches, and bottlenecks in waterways. After filling out a profile of the observed dangers, the data is checked by the lower water protection authority in consultation with the respective municipality and then released.
Other municipalities are also preparing
Other Hessian cities such as Frankfurt, Darmstadt, Limburg, and Marburg have also been preparing for heavy rainfall for years with different measures. This includes the creation of hazard maps, from which flood depths and flow speeds can be read for the respective city area.
In Frankfurt and Marburg, such maps are already available, while they are still being developed in Darmstadt and Limburg. In the future, these maps should serve as a basis for adaptation measures by the city and private individuals, as stated in Darmstadt. This includes the unsealing of areas, decentralized rainwater retention measures, or appropriate street and green area design. These and other measures should be visible in the Darmstadt Climate Adaptation Plan, which is currently being developed and is expected to be published in the first quarter of 2025.
Similar measures are also provided for in the Marburg Climate Adaptation Concept - from the unsealing of areas and the creation of infiltration trenches to the promotion of green roofs to the renaturation of sections of the Lahn and its tributaries. The goal is to reduce rainwater runoff and prevent flooding.
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 adjacent to agricultural land.
Protection against heavy rain hazards is already included in urban planning and land-use planning in many places - for example, in Frankfurt with measures for dealing 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 sealing of areas.
Darmstadt also aims for sparing sealing and low land consumption, with more green areas and unsealed areas. Accordingly, the building plans usually contain corresponding regulations.
Similarly to Marburg, Limburg, according to the city, relies on the concept of the sponge city in current building plans, with green roofs, lower sealing, and the creation of trenches on private properties to retain rainwater. However, since the capacities for the water volumes were not sufficient, as recent experiences have shown, it is necessary to also consider agricultural land and prevent "long periods of bare soil".
The early warning system, implemented in all 23 municipalities of Fulda, aims to mitigate the impacts of heavy weather events. These events, including the one that caused significant damage in North Hesse, can lead to flash floods and property damage.
The German Weather Service (DWD) provides real-time weather data and forecasts, which are crucial in analyzing the situation and triggering alarms when necessary.
