First Observations of Saltmarsh Cliff Erosion Mechanics During Extreme Storm Conditions in a Full-Scale Wave Flume

Abstract Saltmarshes provide many vital ecosystem services, like wave dampening and carbon sequestration. These services are under pressure since saltmarshes are eroding worldwide. The erosion mechanics of saltmarshes are not well understood, especially during extreme storm conditions. Full-scale flume experiments were conducted on a real-life transplanted Dutch Wadden sea saltmarsh with a common brushwood dam protecting the marsh edge, to test the erosion resistance during extreme wave conditions. Little erosion occurred on the marsh platform during 40 h of exposure to various wave conditions, with most of the significant erosion occurring at the seaward edge of the marsh. Erosion was initiated by damaging and uprooting of the vegetation, exposing the substrate and leading to gradual erosion. Uprooting events frequency and erosion rates were higher during high wave conditions and water depths (H m0 = 2 m and d m = 4 m). The brushwood dam did not protect the saltmarsh from eroding at the cliff. Our results demonstrate the erosion mechanics under extreme storms conditions and that uprooting may lead to instability of the saltmarsh on long-term.