Journal Article

Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise

Fagherazzi, Sergio, Mariotti, Giulio

2013

نظرة عامة

High rates of wave-induced erosion along salt marsh boundaries challenge the idea that marsh survival is dictated by the competition between vertical sediment accretion and relative sea-level rise. Because waves pounding marshes are often locally generated in enclosed basins, the depth and width of surrounding tidal flats have a pivoting control on marsh erosion. Here, we show the existence of a threshold width for tidal flats bordering salt marshes. Once this threshold is exceeded, irreversible marsh erosion takes place even in the absence of sea-level rise. This catastrophic collapse occurs because of the positive feedbacks among tidal flat widening by wave-induced marsh erosion, tidal flat deepening driven by wave bed shear stress, and local wind wave generation. The threshold width is determined by analyzing the 50-y evolution of 54 marsh basins along the US Atlantic Coast. The presence of a critical basin width is predicted by a dynamic model that accounts for both horizontal marsh migration and vertical adjustment of marshes and tidal flats. Variability in sediment supply, rather than in relative sea-level rise or wind regime, explains the different critical width, and hence erosion vulnerability, found at different sites. We conclude that sediment starvation of coastlines produced by river dredging and damming is a major anthropogenic driver of marsh loss at the study sites and generates effects at least comparable to the accelerating sea-level rise due to global warming.

• الناشر: National Academy of Sciences,National Acad Sciences
• موضوع: Accretion / Anthropogenic factors / Areal geology. Maps / Atlantic Ocean / basins / Climate change / Coasts / Computer Simulation / dredging / dynamic models / Earth sciences / Earth, ocean, space / Eastern United States / Erosion / Erosion control / Erosion rates / Exact sciences and technology / Geologic maps, cartography / Geomorphology, landform evolution / Global Warming / Inlets / Marine and continental quaternary / Marshes / Modeling / Models, Theoretical / New Jersey / Physical Sciences / River basins / rivers / Salt marshes / Sea level / Sea level rise / Sediments / Shear stress / Soil erosion / South Carolina / starvation / Surficial geology / Tidal flats / Virginia / Water Movements / water waves / Wave energy / Wetlands / Wind / Wind waves