A cross-border mud budget for future sediment management

Abstract The world’s coasts and deltas are progressively threatened by climate change and human activities. The degree at which coastlines can adapt to these changes, especially Sea Level Rise (SLR), strongly depends on the availability of sediments. But despite its importance for coastal adaptation, the availability of muddy sediments is poorly known. This study aims at developing the first mud budget for the world’s largest uninterrupted system of barrier islands and tidal flats: the Wadden Sea. The resulting mud balance is nearly closed: ~12 million (M) ton/year enters the system on its western end, ~1.5 M ton/year is added by local rivers, while we estimate ~12 M ton annually deposits or is extracted by anthropogenic activities. Our data suggests that a mud deficit already exists in the downdrift areas, which will only become more pronounced with increased SLR rates. Mud is thus a finite resource similar to sand, and should be treated as such in sediment management strategies. Resolving future challenges related to climate change therefore requires a cross-border perspective on sediment management.