Turbid waters keep the coast healthy
April 18, 2024 - By NIOZ Royal Netherlands Institute for Sea Research, "To preserve the important intertidal areas and salt marshes off our coasts for the future, we need more turbid water. That is one of the striking conclusions from a new study conducted by a Dutch-Chinese team of researchers and published (https://lnkd.in/e2jVECuD) today in Nature Geoscience. "These natural areas outside our dikes are essential for #nature and #coastaldefense. But because how we are now building in the Delta and the hinterland, coastal defense is endangered in the long term," warns NIOZ researcher Tim Grandjean.
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Satellite measurements
For his research, Grandjean linked decades of satellite measurements of tidal areas around the world with data on the turbidity of the water, which is also measured by satellites. Importantly, Grandjean has established a lower limit for the necessary turbidity of the water in #deltas worldwide. A very clear relationship emerged in the long term: #intertidalareas only grow when the water is turbid enough. "After all, turbid water means more sand and silt particles in the water, which can allow the coast to grow," the researcher explains.
Vulnerable tidal flats due to human interventions
Worldwide, the #turbidity of many #coastalwaters has been declining for decades, making the #tidalflats sensitive to loss. Additionally, sea level rise requires that water has higher turbidity to continue to maintain tidal flats. The relatively low turbidity globally threatens essential areas for #biodiversity and coastal safety. After all, tidal flats are important foraging areas for birds and contribute to wave attenuation.
Coastal defenses must improve
Globally, the determination of the necessary turbidity for the preservation of tidal flats by Grandjean provides an essential basis for rethinking human interventions in deltas. We need to think more carefully about the ways in which human activities affect the coast, on which we rely for our safety. These challenges are not unique to any one region but are evident globally due to extensive human modifications to natural water systems. For instance, the construction of large dams, such as the Three Gorges Dam on the Yangtze River, has significantly reduced the sediment supply downstream. This reduction is crucial for the propagation of tidal flats, leading to sediment starvation that hinders the natural rebuilding of #intertidalzones, vital for #coastalprotection and #biodiversity.
Similarly, in the Netherlands, the construction of the storm surge barrier in the Oosterschelde in the 1980s has led to severe 'sand starvation'. Because of this barrier, less sand can flow from the North Sea into the estuary, resulting in clearer water that fails to replenish the intertidal areas, thus causing them to erode. "In the long run, this is not sustainable..."
#environmentalimpact #geomorphology #physicaloceanography
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