On 14 July 2021, between 60 and 180 mm of rain fell in the Eifel region in just 22 hours - an amount that would otherwise have fallen in several months and which led to catastrophic flooding.
On 14 July 2021, between 60 and 180 mm of rain fell in the Eifel region in just 22 hours - an amount that would otherwise have fallen in several months and which led to catastrophic flooding. The events were far more destructive than existing models had predicted. Researchers at the Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences point at a number of effects that have occurred only rarely in Central Europe so far and have therefore not been taken sufficiently into account. These include, in particular, the mobilisation of dead wood and sediment, both effects that are likely to become more important as climate change progresses. Michael Dietze and Ugur Öztürk report today in the journal Science on the mechanisms that have amplified the effects of the flood. They also give an outlook on a new research project that starts here in order to make future anticipation efforts more realistic.
Researchers as Accidental Witnesses to the Flood Disaster
14 July is a rainy day. GFZ researcher Michael Dietze is on his way back from a field visit in the southern Eifel with colleagues from Potsdam and the University of Bonn. Heading back north, they quickly realise that what is happening just outside is more than a long heavy rain: The online data view of the Altenahr gauge rises rapidly every 15 minutes, faster than the actual forecast, and faster than the researchers would have liked to, because their own measurements are affected. Flooding of the Ahr is nothing unusual: as part of a research project, Dietze and colleagues had set up several seismic stations on a three-metre-high terrace in the Ahr valley a few weeks earlier – assumed to be at safe distance to hostile flood conditions. They wanted to use them to measure ground motion caused by sediment movement and water turbulence during "regular" floods. Now the level is already one metre above the terrace, the stations are lost.
Read more at GFZ Geoforschungszentrum Potsdam, Helmholtz Centre
Image: Woody debris clogging a small creek of the Ahr river, leading to temporal ponding, massive sediment deposition and overbank spillways of the flood water. (Credit: M. Dietze, GFZ)
