Five years after deadly floods, a German valley prepares for the next one

When Alexandra Wiemer recalls the night of July 14, 2021, what she remembers most is water suddenly "coming from every direction." It was 10:30 p.m. when she felt it rushing towards her.

The normally gentle Ahr river that starts in the mountains of western Germany and flows more than 85 kilometers (53 miles) before emptying into the mighty Rhine, had burst its banks.

The region received an entire month's worth of rainfall in just two days, turning the usual trickle into a torrent. The force of the water swept away cars, houses, trees and other flotsam that, in turn, tore down bridges.

Alexandra Wiemer and her son managed to escape to safety, but many others were not so lucky. The flood, the worst in the country's living memory, claimed 135 lives, most of them in Wiemer's town of Bad Neuenahr-Ahrweiler. Some 80% of the town was inundated. The raging waters also caused billions of euros in damage to homes and infrastructure.

Five years on, the valley is one vast reconstruction site, as several billion euros — mostly from state and federal money — are invested in rebuilding and preparing for future floods.

How towns in the Ahr Valley are building back better

One particularly large construction site is located right by the river in Bad Neuenahr-Ahrweiler, right where the water breached the medieval town wall and flooded the historic old town. Now, a new 480-meter-long retaining wall is being built as additional protection.

"It's a very solidly anchored wall, built with bored piles 1.20 meters in diameter and driven 15 meters deep," says Hermann-Josef Pelgrim, managing director of the local reconstruction and development corporation.

Many other safety measures are more subtle, but equally effective, says Pelgrim. They include the construction of a new fire station built on underground stilts to prevent easy collapse. In the inner city, green spaces are being connected to underground drainage trenches to absorb and redirect heavy rain.

The 16 bridges destroyed in 2021 are being redesigned. The remains of a five-arch medieval one will be left standing as a memorial, and its replacement will have just one wide arch to allow water and debris to pass safely underneath.

"This bridge will not collapse under any circumstances," Pelgrim explains, "even in the event of extreme flooding." But he also says preventing another disaster requires a combined, cross-community effort. "We can prepare for what's coming our way. But it would be better if not so much came our way in the first place — and that's the responsibility of those further upstream."

Giving more room to the Ahr river (again)

Old maps from around 220 years ago show the Ahr river meandering freely across its valley floor, sometimes in several branches at once. But as more people moved into the valley, they channeled the river and built along its banks, meaning flood waters have nowhere to go except straight into built-up and agricultural areas.

The town of Altenburg, located a few kilometers upstream from Bad Neuenahr-Ahrweiler, is a case in point. The water levels during the 2021 flood were among their highest here — more than 7 meters instead of the regular 70 centimeters. In an aerial photo taken at the time, only the top floors of houses in the town were visible above the water.

Bruno Büchele, an engineer coordinating the waterway restoration, says the main challenge now is to give the Ahr back its natural space. To do so, the county administration has bought riverside plots from local farmers and private owners to turn them back into flood plains. The idea is to plant the land with shrubs, trees, and bushes.

"But these efforts will only be fully effective once retention measures technically reduce the volume of runoff arriving here," Büchele says. Both he and Pelgrim say flood prevention should start even further upstream — with the construction of dams along the river and its tributaries.

One such dam already exists in a side valley. Just outside the village of Adenau, it spans a stream, turning the meadow behind it into a basin.  When the water rises during a flood, it pools up behind the dam. In 2021, it held 40 million liters of water and though it leaked slightly, it didn't break. A second basin nearby did the same, preventing disaster in Adenau.

Because the system worked so well, 17 more such dams are in planning along the Ahr and its tributaries. But these ones will be much bigger, as high as 25 meters. The projected cost is more than €1.5 billion ($1.7 billion) and construction will take decades — if everything goes to plan.

A new start for old plans

Similar plans for the Ahr valley were made after another devastating flood in 1910 but never put into practice. The flood faded from memory, and the allocated money went elsewhere, including into the construction of the nearby Nürburgring racing circuit.

But even if everything does go to plan this time, Alexandra Wiemer is also taking her own precautions. After the flood, she moved to a different house. Her basement windows now have flood barriers, and she has a stack of sandbags right next to them, partly hidden by shrubs.

"These are precautions," she says, "so that if anything happens, we can act quickly."

Just like all the flood survivors she knows, she has stayed in town — and just as close to the river as she was in her old home. The reason, she says, is simple. "Because it's nice to live by the water. And because I'm not afraid. Period."

Edited by: Tamsin Walker

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