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Places are flooded, dikes are in danger of breaking – floods are becoming more and more common in Germany. The reason is the climate crisis.
Frank Böttcher has been working on extreme weather events for a long time. For him, the flood situation comes as no surprise:
“This is a scenario we predicted for the future 30 years ago. In this respect, exactly what we expect from climate change has happened and what will also be part of the description of the future. We expect longer dry phases, longer drought phases. We have seen this in large parts of Germany and in large parts of Europe in recent years. And we also expect longer periods of heavy rainfall, which will then last longer and be more intense.”
And higher temperatures, such as in a mild winter, can also increase rainfall.
“At two degrees higher, the atmosphere can hold about 14 to 15% more moisture. And this potential for more moisture comes out of the clouds for longer periods.”
“And of course these are often exactly the exact amounts of rain that then have a significantly higher potential for damage.”
“At the same time, the weather conditions are lasting longer and have become a bit more sluggish.”
Serious floods have also occurred in the past. However, they are becoming more frequent and more severe due to the climate crisis.
“Such a weather situation with such high water levels as now, which would otherwise perhaps occur every 80, 90 or 100 years, will then have a frequency of perhaps 50, 30 or 20 years, at some point perhaps even occurring every tenth year.”
Not all floods are the same – which also leads to very different types of damage.
“We have experienced in the Ahr Valley that we have much hillier terrain than, for example, in large parts of Lower Saxony. In the Ahr Valley, 300 liters per square meter in a very short time, within 24 to 36 hours. And then high flow speed, which means enormous potential for damage in a very short time, because masses of water press against buildings with enormous force and simply destroy and tear them away. This is a completely different situation than if I had exactly the same amount of precipitation spread over two weeks in Lower Saxony, where the flow rate is much slower.”
“It is not the case that the houses there are collapsing at a rapid rate due to the masses of water, but that the water simply stands on the foundations for two weeks, the water slowly presses against the houses from below, the ground becomes soft, the houses slowly sink in, become crooked, develop cracks, become unstable and the water that is then in the building will, in the worst case scenario, freeze when there is an impending frost and cause new damage patterns.”
Böttcher believes that many communities are already well prepared for flood situations – for example with mobile dikes. But he also makes it clear: in some regions the best adaptation to climate impacts will probably be resettlement.
“That will happen either through legal frameworks or because insurance for these areas will simply become so expensive or no longer exist at all.”
And he sees another advantage in clearing previously used and built-up areas:
“That would also be a good opportunity to look into creating water storage facilities. Because in the future we will have to see the water that has now come down even more in flood situations as a gift for the phases in which we have long periods of drought. So the question will also be, how can we manage to use the water, which is now too much, so that it is available to us when there is too little.”
It’s not just floods caused by rain that threaten inhabited areas, warns Böttcher. Other climate impacts will also make life in Germany more difficult.
“Of course this also affects the coastal region, it also affects the high mountains. We will see changes in the Alps, in southern Germany. Due to the change in the permafrost that is disappearing there, we have other risks of damage from falling rocks. While we on the coasts will have situations due to rising sea levels that will result in a very significant rethinking of the settlement of our immediate coasts.”
His demand: German municipalities must adapt to regional scenarios – and do so promptly.
“Because one of the few things we no longer have is time.”
