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New Hereon study shows: Too little sand deposition in the German Wadden Sea
The Wadden Sea in the North Sea consists of shallow coastal bays, known as tidal basins. These basins have an important function: they protect the coasts from flooding, for example from storm surges and rising sea levels. A new study by the Helmholtz -Zentrum Hereon shows that most tidal basins in the German Bight no longer have sufficient sediment to compensate for sea level rise. The results were published in the journal Communications Earth & Environment. They are based on an analysis of data from 25 years.
As a result of climate change, rising sea levels are threatening low-lying coastal areas around the world, such as the Wadden Sea in the North Sea. Tidal basins form a natural protective barrier there. They connect the mainland with the offshore islands. They fill with seawater during high tide and empty again during low tide. Sediments are deposited in the process, causing the seabed to rise steadily. In this way, the basins compensate for rising sea levels. This ability to adjust has recently declined significantly. Sea levels are rising faster than the bottom of the tidal basins. This is what researchers at the Hereon Institute for Coastal Systems - Analysis and Modeling have found in their latest study.
Consequences for coastal protection
“Sedimentation in German tidal basins is no longer sufficient to counteract rising water levels,” says geophysicist and co-author Dr. Wenyan Zhang. Only 9 of the 24 basins in the German Bight showed an increase in height that exceeded the relative sea level rise over the period from 1998 to 2022. Looking at the past decade, the number is even lower, at only 4 basins.
Hidden errors in long-term data
The researchers also found that the height growth of tidal basins had been incorrectly estimated in the past. They evaluated data sets on water depth and seabed topography that had been measured over the years using a wide variety of methods and instruments. The result: small-scale structures such as tidal creeks and channels were often inadequately recorded. “This repeatedly led to distortions in earlier studies,” says Zhang. Sediment accumulation in the tidal zone was often overestimated, while erosion in deeper areas was underestimated. The Hereon researchers cleaned up the data sets and corrected previous estimates. "Our study paints a much clearer and more worrying picture than previously assumed in science. It follows that current and future measures in coastal protection and climate adaptation must be significantly more comprehensive and ambitious."
The analysis methods developed at Hereon are crucial for assessing climate impacts and coastal zone management. They offer new opportunities for evaluating geoscientific time series and ensuring data consistency. Based on their findings, the researchers now want to investigate why sedimentation in the Wadden Sea has declined. According to Zhang, various factors could play a role, such as accelerated sea level rise, ecosystem disturbances, reduced sediment supply from rivers, or human influences such as port construction.
Cutting-edge research for a changing world
Helmholtz-Zentrum Hereon`s scientific research aims at preserving a world worth living in. To this end, around 1000 employees generate knowledge and research new technologies for greater resilience and sustainability - for the benefit of the climate, the coast and people. The path from idea to innovation leads through a continuous interplay between experimental studies, modeling and AI to digital twins that map the diverse parameters of climate and coast or human biology in the computer. This is an interdisciplinary approach that spans from the fundamental scientific understanding of complex systems to scenarios and practical applications. As an active member of national and international research networks and the Helmholtz Association, Hereon supports politics, business and society in shaping a sustainable future by transferring the expertise it has gained.
Dr Wenyan Zhang
Co-Author
Institute of Coastal Systems - Analysis and Modeling
Phone: +49 (0)4152 87-1568
Mail: Wenyan.Zhang@hereon.de
Miao, B., Arlinghaus, P., Hagemann, H., Schrum, C., & Zhang, W (2025): Misconception of coastal morphological resilience caused by inconsistent resolution in bathymetry mapping. Communications Earth & Environment.
https://doi.org/10.1038/s43247-025-02974-y
https://Institute of Coastal Systems - Analysis and Modeling
https://hereon.de/institutes/coastal_systems_analysis_modeling/index.php.de
Result of climate change: Rising sea level threaten the Wadden Sea.
Quelle: Hereon/Torsten Fischer
Copyright: Hereon/Torsten Fischer
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