Flood expert: What Germany can learn from the Netherlands

Mr. Bachmann, the flood levels in Germany are dropping again. Does this mean that the danger of an even greater disaster has been averted?

The biggest danger is over for now. The weather looks good: No further precipitation is predicted for the coming days and the water levels will continue to fall. The frost is good for the dykes, the ground is rock hard.

Climate change means that extreme rainfall in Germany is becoming more frequent and flooding more likely. How well did the flood prevention work this time?

Overall, the damage remained relatively low. In many places, the water levels were not that high - except in Lower Saxony and southern Saxony-Anhalt. Basements did fill up in some places, or the water reached the first floor. Of course, this can hit individual families very hard. There have been a few regional hotspots where the situation was critical at times, but all in all, we got away lightly.

Does this mean that the flood regions were adequately prepared for the emergency? Or was it just luck that the water stopped rising just in time?

Both. We were lucky that the water rose rather slowly this winter due to the topography in the affected areas - unlike in the Ahr Valley in 2021 when the flood came very quickly. As a result, it was possible to predict quite well this time how the flood situation would develop locally, and civil protection had enough time to react.

What else worked well?

The dams were managed quite well. In the Harz Mountains, they did run so full in places that they had to discharge. But they also absorbed a considerable amount of the flood water – especially for Lower Saxony.

Have there been things that didn't go so well?

Because the flood remained in the area for so long, the dykes ended up being very soaked. It turned out that many river dykes in Germany - especially on medium-sized and small rivers - are not in the best condition. Today, the standard is to build three-zone dykes: At the front, where the water runs up, the dyke must be sealed with clay, for example. Behind this comes the so-called supporting body, which absorbs the forces. This is followed by a layer into which the water can seep. But on small rivers, which were particularly affected by the current floods, the dykes are often just simple earth walls. They urgently need to be overhauled. There are also trees on some dykes that don't belong there at all.

Why?

Imagine a completely soaked dyke in a storm. At some point, the ground can no longer support the roots of a tree. The tree falls and tears a hole in the top of the dyke. Dykes are structures that have a function to fulfill, and trees have no place on them.

How can we adapt our water management to climate change in the long term?

Overall, we need a smart mix of infrastructure – dykes, water pipes, reservoirs – and nature-based solutions. In agriculture, for example, it was long a matter of course to divert water away from the field as quickly as possible. So we drained, drained, drained. But this is precisely what we are now moving away from. If the soil can absorb a significant amount of precipitation and does not immediately rerelease it via ditches, streams, or rivers, this helps to prevent flooding – but it is also a protection against future drought, the other extreme weather events that we have to prepare for due to climate change. So we need to keep more water in the countryside than before. In cities, it is more about unsealing areas.

But at some point, even the most absorbent sponge landscape is saturated with water. What happens then?

Then you need dykes and dams. However, I believe that one of the most effective flood protection measures is spatial planning. It is still allowed to build in the floodplains of rivers. The Elbe River, for example, has lost more than 80 percent of its former floodplains. No wonder it now runs into residential areas when its level rises. So the rivers need to be given more space again. In some places, a start has already been made.

What still needs to change to improve the balance between the two extremes of drought and flooding?

That will be a challenge. Berlin is already discussing diverting water from the Elbe to the Spree to meet the capital's future water needs. Who gets how much water from where? There will be conflicts over this. In addition, water management as a whole will become more difficult. One example of this is the dams. Their purpose is not only to protect against flooding but also to ensure the supply of drinking water to large regions. Sometimes, they generate electricity using hydropower, or they are popular landmarks. The current flood situation has shown how difficult it can be to reconcile all of this.

In what way?

The dams in the Harz Mountains were already fairly full before the extreme rainfall began in December. As a result, some of them could not hold much additional water and their operators were heavily criticized. But the drinking water supply depends on these dams right up to Bremen. If they hadn't been so full and it hadn't rained so much this winter, drinking water would have become scarce next summer – and the operators would have faced even more criticism.

You say that money needs to be spent to adapt Germany's water management to climate change. Is that compatible with the debt brake?

Personally, I think it's not just about money. We will also have to deal with the shortage of skilled workers. We currently notice at the universities that the number of students in our fields is not necessarily increasing. Excessive red tape is another inhibiting factor. Conflicts of interest have to be reconciled, and that also takes time.

Before joining the university, you worked as a consulting engineer for a Dutch non-profit organization in water, soil and infrastructure. What can Germany learn from the Netherlands in terms of water management?

They have a Delta Commissioner who is tasked with flood prevention. The office is basically independent of politics, similar to the European Central Bank's monetary policy, and is endowed with financial resources for several years. That seems very sensible to me.

What I find most important, however, is the completely different attitude I encountered there. Germany tends to react to disasters, but the Netherlands has a proactive approach to flood protection – Germany can still learn a lot from that. Of course, the incentive in the Netherlands is much greater, as a third of the country is below sea level. This area is very densely populated and there is a lot of high-tech industry there. If it were to be flooded, it would really be a national disaster. Still, I would like us in Germany to take much more proactive precautions instead of waiting and seeing.