ANPBiesbosch at high water
NOS Nieuws•vandaag, 05:02
Rolf Schuttenhelm
editor Climate
Rolf Schuttenhelm
editor Climate
Technically it is probably possible to continue to protect the Netherlands against flooding up to a sea level rise of up to 3 meters. This includes spraying more sand and increasingly heavier dikes, according to a report published today on behalf of the Delta Commissioner and the Ministry of Infrastructure and Water Management.
It won’t be without problems. To accommodate a 3 meter sea level rise, some dikes will have to be made 90 meters wider, says Jos van Alphen, strategic advisor to the Delta Commissioner. This does not fit in with the existing buildings everywhere.
The Sea Level Rise Knowledge Program builds on the new climate scenarios from the KNMI presented last month. These show that the rate of sea level rise this century is very uncertain. It makes a big difference how many greenhouse gases are still emitted worldwide, and whether ice loss in Antarctica can accelerate. The North Sea could rise 1 or 2 meters this century, and around 3 to 5 meters by 2150. If global emissions fall sharply, this will happen much more slowly.
According to the report, if the sea level rises by one meter, 2,100 kilometers of flood defenses will need to be reinforced in the Netherlands. Moreover, up to four times as much sand will have to be sprayed every year. The extractable sand in the North Sea then becomes a limiting factor. “We need a lot more sand,” says van Alphen. “And therefore also tighter control over the use of space in the North Sea.”
NOSThe latest sea level scenarios for the North Sea. It is still uncertain whether the ice loss in Antarctica can accelerate itself and thus gain momentum (see dotted lines).
In the interim report, the Sea Level Rise Knowledge Program mainly looked at technical feasibility. But there are also fundamental choices open. Knowledge Institute Deltares was previously commissioned to create four different long-term scenarios to develop. In two of those scenarios, much more space is created in the low-lying parts of the Netherlands to collect water.
Pumping the Rhine to the sea
We encounter a fundamental problem with dikes there, says professor of physical geography Maarten Kleinhans of Utrecht University: with a boarded-up coast we can run into problems with other water problems. It is becoming increasingly difficult to allow the water of the major rivers to flow from high to low to the sea. That river water may have to be pumped to the sea using huge pumping stations. Kleinhans previously estimated that dike increases beyond 2 meters of sea level rise are no longer useful.
When the dike is raised, the polders behind it also become deeper. That makes it more difficult to pump away precipitation. This extra drainage also draws salty groundwater to the surface – a problem for agriculture. For example, there is a threat of a shortage of fresh water for the Netherlands, especially if the rivers become lower in the summer due to climate change.
Then we have the highlights of current coastal protection: the storm surge barriers – lockable barriers, for example in the Nieuwe Waterweg and the Oosterschelde. Storm surge barriers will increasingly have to close and eventually even be replaced, the authors write. The Oosterscheldekering may have to go, Jim van Belzen of the Royal Netherlands Institute for Sea Research (NIOZ) recently suggested.
Four times as much sand
According to the report, if the sea level rises by one meter, 2,100 kilometers of flood defenses will need to be reinforced in the Netherlands. Moreover, up to four times as much sand will have to be sprayed every year. The extractable sand in the North Sea then becomes a limiting factor. “We need a lot more sand,” says van Alphen. “And therefore also tighter control over the use of space in the North Sea.”
In the interim report, the Sea Level Rise Knowledge Program mainly looked at technical feasibility. But there are also fundamental choices open. Knowledge Institute Deltares was previously commissioned to create four different long-term scenarios to develop. In two of those scenarios, much more space is created in the low-lying parts of the Netherlands to collect water.
Pumping the Rhine to the sea
We encounter a fundamental problem with dikes there, says professor of physical geography Maarten Kleinhans of Utrecht University: with a boarded-up coast we can run into problems with other water problems. It is becoming increasingly difficult to allow the water of the major rivers to flow from high to low to the sea. That river water may have to be pumped to the sea using huge pumping stations. Kleinhans previously estimated that dike increases beyond 2 meters of sea level rise are no longer useful.
When the dike is raised, the polders behind it also become deeper. That makes it more difficult to pump away precipitation. This extra drainage also draws salty groundwater to the surface – a problem for agriculture. For example, there is a threat of a shortage of fresh water for the Netherlands, especially if the rivers become lower in the summer due to climate change.
Then we have the highlights of current coastal protection: the storm surge barriers – lockable barriers, for example in the Nieuwe Waterweg and the Oosterschelde. Storm surge barriers will increasingly have to close and eventually even be replaced, the authors write. The Oosterscheldekering may have to go, Jim van Belzen of the Royal Netherlands Institute for Sea Research (NIOZ) recently suggested.
NOS
If sea levels continue to rise, the storm surge barrier will eventually close permanently. (The KNMI’s highest sea level scenario is not included here.)
NOS
Dike widening/raising weighed against sea level rise
The problem is that the Oosterscheldekering slows down the tide and stops the supply of sand to the Oosterschelde, Van Belzen told NOS. “The Oosterschelde is drowning. This will accelerate due to sea level rise.” The National Park is attractive in nature precisely because of the daily drying up of sandbanks and salt marshes.
Van Belzen therefore advocates an open Oosterschelde. If the tide is given free rein again, the area can rise again naturally. He also thinks that it will be cheaper for us. “The underlying dikes must then be as strong as those on the Western Scheldt. Maintenance of a storm surge barrier is financially unfavorable compared to this.”
Board up
Boarding up the coast is not simply the best option, says Kleinhans. “It is still viewed too much from the technical possibilities. But we are still faced with very different questions: where do we want to live, how do we want to work, what guarantees do we offer for natural life and how do the costs relate to the benefits? I dare It’s almost impossible to say, but much more research is needed here, from many more disciplines.”
Yet the time to make decisions is approaching faster than ever sea rises. This is because one strategy can be at odds with the other. “We are making important investments of hundreds of billions in housing and infrastructure for a hundred years or more,” Van Alphen concludes. “So we have to think now whether we are doing this in the right place.”
2023-11-09 04:02:21
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