Reviving Germany's river landscapes

We have been altering river landscapes for hundreds of years for industry, energy, farming and building houses. River courses have been straightened, regulated, diked and deepened across the world.

Parts of their floodplains, which would usually provide space for overflowing water, have been drained and filled — sometimes with the idea that this could prevent floods. But it turns out: The opposite is the case.

We messed up rivers

In Germany alone, two-thirds of the floodplains along the 79 main rivers can no longer serve their original purpose of storing excess water because of the dikes built to stop water from reaching them. One third of the remaining floodplain areas are covered by fields and houses. 

And that's not just the case in Germany, but across Europe, where 70-90% of floodplains have been environmentally degraded. 

And we're paying the price now. As climate change brings more weather extremes, these altered landscapes are more prone to destructive flooding.

An urban wetland region in Germany's east recognized the problem early on.

"We realized 30 years ago already that our industrial, technical advancement has made the forest in this region develop in a wrong direction, that our ecosystem isn't resilient anymore. And that we need to go back to the old ways and let nature work for us," said Mathias Scholz, a floodplain ecologist with the Helmholtz Centre for Environmental Research in Leipzig, who has been studying the role of rivers and coastal wetlands for decades.

Why we need functioning floodplains

Healthy, functioning floodplains are very important for us, explains Scholz, as they retain water in the landscape for a longer period and act like a sponge. They are natural climate protectors and flood controllers — but only when they are supplied with water. 

"This helps plants better withstand drought summers. And when the next flood comes and the river overflows its banks, it can flood nearby forests and meadows. This is one of the most effective insurances against flood damage, as part of the floodwater stays in the floodplain instead of rushing downstream and causing destruction there," Scholz said.

If we no longer have floodplains and floodplain forests, the water flows out of the landscape very quickly, leading to increasingly larger flood waves that cause significant damage. And that's exactly what's been happening more and more in recent years.

That's why Scholz — together with the cities of Leipzig and Schkeuditz, the University of Leipzig and Germany's environmental association NABU — decided to give the floodplain landscape in this area a more natural face again. 

"Many trees developed here that are no longer flood-resistant, displacing the tree species typical of the floodplain forest," said Scholz.

One example are oak and elm trees, which started to die off when they didn't get enough water anymore after the floodplain forest was cut off from the rivers. The problem is, these native trees can handle floods and droughts better than other non-typical species that started spreading, such as maple.

And oak and elm trees suck moisture out of the soil, which decreases the amount of water contributing to flash flooding events.

Training forests to help soak up water again

So, the researchers had an idea. They started purposely flooding a small area of the forest every spring for decades. And measured the results. The data they collected over 30 years tells the story of an ecosystem going back to its natural state.  

"We realized that we can maintain moist conditions in the forest for up to three months longer, even during drought periods, allowing the floodplain forest to adapt to these wetter, more dynamic conditions. At the same time, other species that do not belong here receded, providing space and light for tree species typical of the floodplain forest," Scholz said.

They literally trained the forest to be able to soak up more water again. And that's important, because even if trees are flood-resistant, if they do not experience flooding for a long time, they may "forget" how to cope with it or adapt to it, says Scholz.

"Therefore, it is important to train these ecosystems to handle water again, so that they do not collapse after the first flood event."

Revitalizing old water courses

Spurred on by the positive results, the city decided to do more. It brought together scientists, NGOs and local officials in 2019 to come up with a concept to rejuvenate the entire floodplains here over the next 30 years.

And they just finished their first project. They restored a historic riverbed and moved the river field relatively far away from the forest edge. And they created several exit points where, when the flood comes, the water can rise and then flow over the very shallow bank directly into the forest.  

"I am so very happy right now, because it was five years of hard work, of discussions, of talking to people every day, ensuring that they are not afraid when a bit of water comes," said Christiane Frohberg who's with the city of Leipzig's Department for Urban Greenery and Water Bodies. "And it's just wonderful to see that we now have water in this small river, which nevertheless has a significant impact," she added. 

The goal for the next 10-15 years is revitalizing more than 16 kilometers (about 10 miles) of former river paths in this region. They want to reconnect dried-up river arms and flood at least 30% of the floodplain area via the new river to give the floodplains their natural face again.

But that will take a lot of time, money and negotiations.   

What's the price tag?

Projects like this come with a hefty price tag. The city of Leipzig already spent 6.5 million euros — largely funded by the German state — to buy back land and build new bridges and gateways for crossing the newly restored river. Especially getting the farmers in the region on board was tricky.

"You can't simply expropriate people without offering alternatives," said Scholz.

"But bringing more water into the landscape doesn't necessarily mean giving up agricultural use; it just means that agricultural practices need to be adapted. So, this means that transitioning from arable land to a wild pasture must ultimately be achieved, but this change must also be appropriately compensated," he added.

It sounds like the city is spending a lot of money on their restauration project — but flooding is actually the most expensive natural hazard in Europe, with a studyestimating that river-based flood risk could increase ten-fold to €9.3 billion by the end of this century. 

Most large European cities are situated on floodplains. Hamburg, Paris, Florence, Zaragoza, London, Geneva, Ghent and Linz are the ones that are predicted to suffer most flood damages in the future, according to the study.

That's why EU Environmental Ministers recently approved a contested Nature Restoration Law that seeks to regrow forests, re-wet moors and return rivers to their natural, free-flowing states. A move that Scholz welcomes.  

"When we consider the monetary damage that extreme events ultimately inflict on our society and the long-term efforts required to address them, it becomes clear that investing in ecosystem restoration is a future-proof investment," he said.

Transferring knowledge

And more and more European cities situated in floodplains are experimenting with nature-based approaches. The project in Leipzig has become a blueprint for others. Scholz has been cooperating with colleagues from Estonia, Spain and Portugal to share knowledge and best practices, such as how to retain water in an area as long as possible. 

"My advice to all places across the world is: protect what you already have, don't get rid of more wetlands, recognize your potential and invest in nature-based solutions. By restoring an ecosystem, we make the system more robust, reducing the potential damage for future generations," Scholz said.

"This may cost you some money at the beginning, but it will pay off in the long term. Because the next extreme weather events will come for sure, and damages from that will be much more expensive than your initial investment."

Edited by: Sarah Steffen