People in Germany experienced a summer of extremes, although it had relatively little to do with El Niño. Summer 2016 in Germany and Central Europe may have been only slightly warmer compared to the international reference period (1961-1990) and average precipitation was not conspicuous. However, heavy precipitation in early summer, in particular in Germany's southern and western regions, unleashed a destructive force on a scale hardly imaginable. Severe storms with extreme amounts of rain in some regions and sometimes catastrophic effects occurred, for example in the Bavarian town of Simbach, where 180 litres/square metre rain fell in just 48 hours. It was caused by the unusually long-lasting low pressure system called "Tief Mitteleuropa". These weather conditions prevailed on 10 out of 14 days between late May and early June and, even more unusually, on seven consecutive days.
Dr. Paul Becker, Vice-President of the German Meteorological Service, said: "Climate model projections indicate that such weather conditions triggering heavy rainfall will occur more frequently in the future. The torrential flooding this year could be a foretaste of the summer in a warmer world to come. And that is not all: it could happen anywhere in Germany. We must be prepared for this by making even better weather forecasts, citizens must assume more individual responsibility, and we must develop a new culture of dealing with natural hazards."
The vulnerability analysis done by the Federal Government last year is based on this knowledge; its results are unfortunately corroborated by this year's intense rainfall events. The progress report on the Adaptation Action Plan II of the German Strategy for Adaptation to Climate Change derives concrete recommendations on how Germany can better prepare for these extremes. Climate protection objectives and efforts remain important so that the demands made in adaptation measures are kept realistic.
President Maria Krautzberger of the German Environment Agency said: "Summer 2016 has shown that it is becoming more and more important to adapt to climate change. The German Environment Agency recently honoured exemplary local adaptation measures, for example precautionary measures to protect against heavy rainfall, through the Agency's Blauer Kompass contest. The aim is to take the impact of climate change into greater account as early as the urban planning stage. For example, cities should be designed to allow rainwater to drain without causing damage, either on rooftop gardens or public spaces which can be flooded temporarily. Recent events also show how important the dual strategy of climate policy is: broad-based climate protection measures which target the causes of climate change and achievement of the Paris Agreement goals on the one hand, and measures to adapt to the now inevitable climate change whose impact we are already feeling today on the other."
High-resolution risk maps help to take the right action in extreme precipitation events. However, Germany's heavy rainfall mapping system is still in its infancy. The city of Unna is one of the few cities which has such a map showing flow paths and where flooding occurs during intensive rainfall. The information provides a basis for taking sound precautionary measures, for example improving the waterproofing of cellars.
In addition to better early warning for citizens and making self-provisions, the third main factor in the adaptation process is prevention. Urban development which is attuned to the water issue can include planning for interim storage of sudden masses of rainwater or aid stormwater runoff through the restoration of pervious surfaces. Cities like this are "sponges" which can prevent flash floods or flooding in general. Hamburg's green roof strategy is an example: greened roofs slow down rainwater runoff and help to curb the urban climate effect.
All these measures not only reduce climate-related risks, they also have other positive effects for society and the environment: a healthier urban climate, more diversity of species and an overall higher quality of life. Even if flash flooding does not occur, citizens will not regret the changes brought by a double "no-regret" measure.
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The Deutsches Klima-Konsortium e.V. (DKK) represents the leading players of German climate and climate impact research, including universities, non-university research institutions and federal authorities. The DKK offers knowledge-based policy advice, addresses current climate issues and provides expert background information.