By: Michaela-Františka Kárná & Benedicte Christiansen
Floodings in Ribe have been a problem for centuries. Both the citizens in the city
and in the countryside have had their properties flooded. The streams that run
through the town are overflowing more because of heavier rainfall that will only
increase as the climate changes. Residents complain about the inaction of the
municipality and there is also the issue of the ‘cultural layer’ all the houses in the
town stand on. Is Ribe at risk of sinking like the famous Italian city Venice?
Ribe is located on the southwest coast of the Jutland peninsula, close to the Wadden
sea. The city is intertwined with streams and ever since the town was founded in the 8th
century, flooding has been a problem – both from the sea in the west and from the streams in the east. Since people have been dealing with floods for centuries in this area, Ribe has several mechanisms in place to help minimize their impact on the town.
From 1911 to 1915, the seaside dikes were made. They stretch 18,5 kilometres along the
line of the marshland, and they go up to seven meters above sea level. The dikes are
manmade, but they resemble a natural, slowly rising hill, so that if the water ever comes
up on the dikes, the waves will be broken up by the dikes’ hilly construction.
The last time the dikes have been strengthened was with marshland clay after a big
flood in the 1990s.
Gate to the sea
To secure a passage of the stream water through the dike to the sea, a construction called the Waterway Lock (“Kammersluse”) was built in 1912. This is, like the dikes, seven meters tall.
It resembles a mechanical gate between the stream and the sea, that is controlled by the tide. It closes automatically when high tide comes, so the high sea water doesn’t pass through. When the sea level drops back to low tide, the release of pressure opens the gate again. The water that has accumulated in the stream on the other side in the meantime, can then freely flow into the sea.
Only one storm has made water go over the gate which was during an especially strong hurricane in 1999.
However, none of these solutions have stopped the floodings in Ribe completely.
As Niels Frederiksen, 69-years-old citizen of Ribe explains, most of the floodings are caused by water coming from the east of the country.
“When it rains a lot in the east coast of Jutland, most of it comes to the west. We get water from around 500 kilometres of small rivers – it lands all here. Therefore, we’ve got water all the way from Kolding [town on the east coast of Jutland],” he says.
This happens because the landscape towards Ribe in the west is slightly downhill, compared to the east. The terrain was shaped by the last ice age, where the ice and clay were pushed into a certain part of Jutland and when it stopped, it created an uneven landscape.
Flooded yards and basements
Frederiksen has helped many people with their flooded homes over the years. An area he always must go back to, is Holmevej street. It is one of the places that are known for getting flooded the most as it is located close to a stream.
Tina Kodbøl, a 55-years-old shop owner, lives on this street with her family. Her basement gets flooded at least once every year.
“The last time it was really really bad. It was hard wind, so the Waterway Lock has closed, and it has been raining for quite some time. So the water just came up by the river and up over the grounds around the houses and over the road,” she says.
Luckily, their basement is quite deep, so even if it were fully underwater, her family could still be able to live there.
“But you also have to think about the value of the house. You feel like you have to make it [the water] go away to keep it away, so you stay up all night and you vacuum the water, and you have pumps and tubes…It takes a psychological toll,” she describes.
Sometimes, not even staying up all night helps.
“We can pump it out but only as long as we have electricity. And the last time the electricity also got flooded. We couldn’t even pump.”
Kodbøl admits that she considered moving away from Ribe, or further from the stream at least.
“Just after the flooding, you’re so stressed and you think ‘I don’t want to go through this again’ but as always, we stay. Just like people living in places with earthquakes. You tell yourself it’s not going to happen tomorrow, it’s not going to happen this year and you just keep on living.”
She also doesn’t feel properly equipped for any future flooding. They can prepare the pumps in the basement, but if the electricity stops working again, they will have to rely on carrying the water out in buckets.
“It all ends up with us wishing the municipality will do something. They are all so interested in flooding when it’s happening, but after a month, they forget about it,” Kodbøl concludes.
Climate change and weather challenges
Moreover, as the climate is changing and the weather is getting more unpredictable, it could start getting even worse. The streams primarily flood because of heavy rainfall, explains Ove Kann, a biologist who has worked with the streams and water around Ribe for more than 20 years.
“The rain and storms have gotten worse over the years. It is climate change. During my time here, I know that the average rainfall has grown from 800-850 to about 900 millimetres per year,” Kann explains.
Kann further describes that because the planet is warming up, more water evaporates from the sea and condenses into clouds.
“The clouds are coming from the west and when they reach the land, they rise up and cool down. Then they lose the humidity as rain,” he says.
The flooding will be the strongest when cloudbursts happen, because they can last for a few days. This often occurs in the summertime, as the heated seawater creates more clouds, which in turn makes the air very humid.
He also adds that “Ribe could end up similar to Venice. For the next 80 years we can expect a higher sea level up to about 80 centimeters. We might have the dike, but it could still flood.”
The citizens of Ribe have also noticed this.
“It has gotten worse over the years, because of climate change. There’s more water coming from the east now. It’s raining more and heavier. And we got more storms from the west and therefore the Waterway Lock is closed, and the water can’t get out. In that way, we have a lot of water around Ribe,” describes Frederiksen.
Watch the video with Anne Mette Sleimann, who lives just outside the city but still experiences flooding on her property.
What are the organic layers or ‘the sponge’?
However, the water coming in is not the only problem Ribe is facing. Because Ribe is more than a millennium old town with a medieval city centre, the houses stand on top of several geological organic layers. These are also called the cultural sponge or just “the sponge.”
“Ribe has a double problem. We have this cultural layer. If you dig down here, there are about five meters of the sponge. The original ground was when the church was standing the highest, on a hill. Now it has sunken almost downhill. Therefore, it must not dry out. Then all the houses would break up. We need the water,” says Frederiksen.
The sponge consists of compressed old materials, debris and animal waste, such as dung. It needs moisture in order to stay at the same level, because if it dries out, the sponge will shrink, sometimes up to only three meters instead of five, making the foundation of the houses unstable.
This could make the buildings sink, tilt, or, at worst, collapse. So not only would people lose their living quarters, but Denmark would also lose its oldest city – an important historical and cultural landmark.
There are already clear signs of this happening on some of the houses in the town centre. Parts of walls have sunken in the ground, windows or doors have tilted, and roofs have shifted, making the houses look uneven and crooked.
According to the Ministry of culture, Ribe is the best-preserved medieval city in the country, and it is also considered the oldest town in Northern Europe. Many of the houses are preservation-worthy and protected by the state. Any damage to the historical centre is therefore unwanted.
Possible solutions
Because of these geological and cultural layers beneath the city centre, there needs to be a system made for the sponge to stay moist, since the sponge is at risk of getting too dry, especially in the summertime.
Several solutions have been proposed to the municipality of Esbjerg that is responsible for Ribe. Some by its citizens, and one by an architect from Aarhus. Mikkel Kieldsen made it the case of his master thesis.
He suggested building seven water towers around the town, made of the same materials as the surrounding buildings to blend into the landscape.
“The towers would collect water from the sky when it rains or when there’s a low enough fog. They would then lead the water down into a tank, where the water could be stored from April until September – that depends on how dry it is. The citizens could then open the water tank so the water can slowly seep out into the ground.”
That would require a pipe system under most of the houses. Kieldsen says, that could be arranged by digging up a small hole outside the perimeter of the homes and shoot the pipes under it. Therefore, the layout of the town would not be disturbed.
Kieldsen’s project also had another goal.
“In Ribe, they are very aware of the cultural sponge, because it affects their homes very dramatically. And they talk about it a lot. But when you walk around, you can’t really see it. It’s like hidden away. You can’t interact with this very strange phenomenon, which is under the entire town that everybody comes to visit when they’re there.”
“Therefore, I wanted to do something that makes it visible. Not directly, but it makes it present by building towers. I didn’t want to completely detach the citizens from where they live. It was very important to me to have the citizens involved in that process, so they don’t forget why they love to live there. And don’t forget those 800 years of… Of horseshit.”
However, the idea of the water towers is not welcomed by all.
“I don’t think it could work. It would be ugly,” the biologist Kann expresses his dislike. He also raises the issue of the fish residing in the streams of Ribe.
Fish can’t fly
The salmon and the trout that are native to the area have been struggling to swim through the weirs that have been made to stabilize the amount of water coming through the streams. To secure the flow of fish and to maintain their spawning places, the stream needs to be handled with care, Kann describes.
To bring both parts of the streams on the same level in the streams, he suggests to dig deeper underground, and move the bottom beam of the weir lower.
Additionally, there would need to be a “water staircase” made for the fish. This could be done by degradingly removing material from the bottom of the stream, so it creates a slowly rising hill. Then the ascent wouldn’t be as steep, and the fish could easily swim upwards towards the weir and still be able to pass through the streams.
This could also prevent flooding in the city, as the lowered weirs could hold up more water. However, this would require a lot of time and resources, the biologist explains. He believes that is why the municipality has not acted on the matter yet.
Lack of proper data
These are only some of the several issues the Esbjerg municipality has to keep in mind when making future plans for Ribe.
“The deeper we go in, the more we think that the first step to take is to develop a hydrological model for Ribe because it’s very, very complicated. You have the flood risk from the river system, we also have the storm surge risk from the Wadden Sea, where we have the dike and the Waterway Lock and then there is, of course, the sponge. There are also rising sea levels and more rain due to climate change. So there’s a mix of six or seven challenges at play,” describes Bodil Ankjær Nielsen, head of climate adaption and flooding from Esbjerg municipality.
She understands why the people of Ribe have been unsatisfied with no solution being presented yet, but it is not something that is just going to “get there tomorrow,” she explains.
Esbjerg municipality has been obliged to take care of the city Esbjerg, north of Ribe, as a first priority, because it has been designated by the government as a city under higher flooding risk. Therefore, they have had to deal with the city of Esbjerg first, because when the municipality gets a designated city, they need to act on the matter within a year.
Now is finally the time, Bodil Ankjær Nielsen can start to work on Ribe.
“We are in the very beginning of developing climate adaptation and risk management plan for Ribe… To make the best solutions, we don’t have enough and exact data. To balance these things, the first thing we did was asking the Danish Geological Institute (Geos), to assist us in developing this model,” she says.
This will be the beginning of solving the several issues that Ribe is facing. Nielsen also describes that taking on the case of Ribe will possibly be the most difficult task of her time in the municipality of Esbjerg. It will be done with updated reports, new collections of data and meetings with landowners who own land that is along the streams of Ribe.
Renewing the old flow
Some citizens believe that the municipality should start with getting rid of a canal that has been built on the river between the Wadden Sea and Ribe in the first half of the 20th century. It was used as a shortcut for large trading ships, as it made the water in the canal deeper and flows quicker.
But Ribe is no longer one the most important shipping ports, so there is not a need for this canal to remain, as there are no large cargo ships sailing to the town.
If the original stream of the river was renewed, the water could return to its natural flow and more of it would stay in the land. It would also minimize the flooding risk. However, that would turn the fields surrounding the stream back into the original marshland, making the resident farmers lose some of their income.
Nielsen also thinks this could work, but she stresses that it would require difficult negotiations with the owners of the mentioned land, since it is required by Danish law, that it is the owner, who has to take care of possible flooding. The municipality wants to help the citizens manage that in the future.
Complex problems require complex solutions
Before the negotiations can start, the municipality will have to create a hydrological model for the whole area of the medieval city and the areas around the city center.
“Deciding what solution works will take some years. There are so many different stakeholders in the area, such as farmers, but there are also people living in the city and we have some residential areas in the northern part of Ribe, established in the 70s, 80s and 90s. It will take years,” she says.
While considering these different interests in Ribe, Nielsen will also ask for help from colleagues of other municipalities, the EU, and look to the Netherlands for inspiration, because they have been dealing with similar problems in their coastal cities for years.
Caution when looking for solutions is something the municipality has in common with the citizens of Ribe. As Frederiksen says, “All these types of different possibilities need to be looked at. And see what works. Because if we do something, it will inevitably influence something else.”