Excavation threatens Dutch delta due to sediment loss

Rivers and harbors around Rotterdam are already losing more sediment as a result of excavations, and that loss could increase further in the coming century, according to research by Utrecht PhD student Jana Cox. According to him, the effects of the Dutch Delta are far greater than climate change.

Shipping lanes on ports and rivers connecting Rotterdam with the sea Dug to prevent large ships from landing. It needs to go even deeper because the ships are getting bigger. Currently, 2 billion kg of sediment is lost every year as a result. “It’s enough to fill the T-queue for rafters every year,” Cox says.

Along with others, a geologist at the University of Utrecht studied the impact of climate change and human activity on the ‘sedimentary budget’ in the Rhine-Meuse Delta. This shows that sediment loss will increase significantly in the coming century. In 2085 it will not be less than 12 billion kg.

Due to climate change (more storms and floods) the delta will receive 20 to 30 percent more sediment over the next fifty years, but excavation removes more sediment each year, Cox concludes. “It is not climate change, but excavation, that determines the future of the Dutch Delta,” he concludes.

Sediment budget
This year’s sediment loss is called the ‘negative sedimentation budget’: the amount of sediment leaving the delta area is greater than the amount entering. The amount of sediment in the Dutch Delta is ‘red’, similar to a bank account. This means that valuable material for bank security is lost.

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In addition, the dredging work will damage infrastructure such as underground cables and flood barriers. “And valuable southern natural areas may be completely lost in the future,” Cox said. “For example, the Haringvliet is home to unique birds.”

The problem is not exclusively Dutch, he insists. China, Vietnam, the United States and other major deltas in Australia also require more excavation with competing ports on riverbanks and lower river tributaries. “As a result, the most important building block for holding these deltas above rising sea level is eventually lost.”

Solutions
Nevertheless, according to the PhD candidate, there are solutions to increase the negative sedimentation budget and to place the sediment in a sensible place in the delta to prevent it from collapsing and sinking into the future.

At Ems and Western Scheldt, for example, tests are already underway to see if sediment can be used to reinforce curves and curves. The next step in his research is to see how such local and small-scale solutions can be measured for deltas around the world.

“Another solution is to move the port for larger vessels to Maasvlakte 2 and from there move further inland with smaller vessels. Fortunately, this is already being considered.”

More info
Article ‘Climate change and sedimentation and sedimentation budget of the urban delta: an example of the lower Rhine-Muse delta distribution network’
Video explaining the study

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