The changes to the climate over the past few decade have become more and more noticeable. Reports of long periods of heat and drought, as well as unusually heavy rainfall are becoming more frequent, affecting life both in the city and in rural areas. It is common for regions to receive precipitation levels that are either well below or above average, making traditional rainwater management difficult.
FACTS: EXTREME WEATHER CONDITIONS IN GERMANY
According to ZDF, the northeast of Germany, particularly around Berlin, Cottbus and Magdeburg, have the least rainfall, with generally under two litres of precipitation per square metre.
Days with temperatures above 30 degrees Celsius have increased from 3.6 days between 1961 and 1990 to 8.1 days in the last 30 years.
The consequences of these changes are increased droughts and forest fires.
In southern Germany, particularly in the region around Hagen, the number of days with over 20 litres of precipitation per square metre has increased significantly over the last 30 years, currently standing at 4.9 days.
Climate experts predict that extreme weather events in Germany will occur more frequently and become even more extreme in the coming years. Excessive building and agricultural density, as well as exceptionally wet or dry soil additionally disrupt the absorption and storage of precipitation by the earth. In contrast, forests seem to be particularly resistant to climate change. If you look at the balanced water budget of a forest, large trees in particular act as natural air conditioners through evaporation via their leaves. But, is it possible to move our cities closer to our forests in terms of environmental resilience?
AMAREX — Adapting the management of stormwater to extreme events
The AMAREX project is investigating ways of adapting stormwater management to the increasing extreme stresses caused by climate change and thus serves climate impact adaptation. It can be subdivided into different interacting areas. Its ideas are being investigated and applied in the cities of Berlin and Cologne. The project is scheduled to run for three years, starting in February 2022.
In the areas of drought and heavy rainfall prevention, the focus is on expanding the functions of existing rainwater management. Rainwater management is understood to describe the various measures taken in order to handle rainwater in urban areas through utilisation, infiltration and evaporation. This promotes groundwater recharge as well as reducing heat in the city through evaporative cooling.
The aim is to adapt the preexisting stormwater management measures to whatever changes are occurring to the region’s climate. These additional measures should be as natural as possible — such as the promotion of more urban greenery and the creation of more ponds and canals. The practical planning and implementation potential of the AMAREX project is already underway in pilot areas.
The area of drought prevention is supported by the GIS geoinformation system, which is used to collect geodata for digital terrain models and area information. The geodata is additionally supplemented by climate data on temperature and precipitation. The aim here is to analyse the potential of rainwater for the irrigation of urban green spaces. In addition, models will be used to calculate the storage, treatment and provision capacity. In cooperation with the project partner HELIX, the irrigation of green facades with stored rainwater as well as evaporation capacities and plant growth will be investigated using a detailed database.
The area of heavy rainfall prevention also works with the GIS geoinformation system. In this way, potential flooding areas can be identified. In addition, the simulation software InfoWorks ICM is used to create a hydraulic flood model and comparative model simulations. Often, solutions such as naturally constructed infiltration ponds can absorb an excess of rain and slowly release it into the surrounding area.
In the area of reduction and climate impacts, a web-based tool for mapping the effects of rainwater management on climate impacts in urban areas is being developed based on the water balance model ABIMO 3.2. This is intended to support early consideration of climate adaptation in urban strategies and planning. In addition, two areas deal with the dialogue of all relevant actors within the municipalities on stormwater management and the development of an assessment tool afterwards.
AMAREX’s prospects are far-reaching
Although the IPCC’s World Climate Report reminds us every year how serious the climate crisis situation is all over the world, there is some room for manoeuvre. In addition to serious intentions in the reduction of greenhouse gases such as carbon dioxide, we can prepare our cities and municipalities for climate change in the best possible way through sensible measures.
Ideally, this is done through projects like AMAREX, in which science, municipalities and companies work together and jointly develop differentiated and successful solutions for pilot areas. The measures and tools already tested can then be transferred to other, similar regions on a large scale in the next step.
“The importance of functioning and, above all, well-adapted stormwater management will increase as the consequences of climate change become more and more noticeable and should be an integral part of planning processes in the future. The solutions developed for this should be easy for municipalities to apply,” explains Matthieu Rigal from the project partner Technologie Stiftung Berlin.
The prospects of the pilot project are positive, as “similar projects on climate impacts have already shown that there is great potential for solutions in decentralised rainwater management, for example through green measures, such as green roofs or façades, and blue measures, such as ponds and canals,” says Dr. Andreas Matzinger from the project partner Kompetenzzentrum Wasser Berlin (KWB).
Since our cities will have to become more climate resilient in the future, it is worth comparing the urban water balance with the balanced water balance in a forest. Dr. Andreas Matzinger says: “The starting point is the observation that the rain that falls in the city largely runs off via the drains, and in return lacks the water for percolation and, above all, evaporation of a forest or meadow. This shift in the local water balance in sealed cities is responsible for the negative climate impacts that occur there.”
If we take the water balance of a forest as a model and derive solutions for sustainable rainwater management in our cities from it, many of the negative climate impacts can be reduced, at least in part – this is the hypothesis of AMAREX. The future will show whether cities can actually be turned into forests in the long term by means of green-blue measures!
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