Historical evolution of mud deposition and erosion in intertidal areas of the Scheldt estuary

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Chen Wang, Joris Vanlede, Wouter Vandenbruwaene, Yves Plancke, Stijn Temmerman

Monday 29 june 2015

14:53 - 15:05h at South America (level 0)

Themes: (T) Special session, (ST) Scheldt Estuary physics and integrated management

Parallel session: 2J. Special session: Scheldt Estuary physics and integrated management

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The mud dynamics in an estuary are known to be a key element of estuarine functioning, as increasing suspended sediment concentrations may be both harmful for ecological functions (e.g., biomass production by phytoplankton) and human functions (e.g., siltation of shipping channels). Considering the potential risk of increase in suspended sediment concentration in the Schelde estuary (Belgium and SW Netherlands), this study aims to quantify the mud deposition/erosion in different time periods since 1930 to present, different intertidal ecotope types, and different zones along the Schelde estuary. We analyzed the height change, volume change, eroded or deposited mud mass, and the overall mud balance in between time steps of around 1930, 1960, 1990, 2000 and 2010. Our results suggested that netto mud deposition occurred in intertidal areas in almost all time periods and all zones along the estuary. In general, mud deposition was more in the intertidal areas in the Westerschelde (on average 42.6 × 103 ton/year averaged over all time periods) than in the Zeeschelde (on average 36.2 × 103 ton/year). The average mud deposition rate in all the intertidal areas is the largest in the periods of 1963-1992 in the Westerschelde (79.5 × 103 ton/year) and 1930-1960 in the Zeeschelde (72.0 × 103 ton/year). A major part of the intertidal mud deposition takes place in stable marshes, espially in Saeftinghe. A smaller but still important amount of mud deposition is also observed in stable intertidal flats and areas that shifted from intertidal flat to marshes or from subtidal zone to intertidal flat. Over 90% of mud erosion is observed in areas that shifted from intertidal flat to subtidal zone in the Westerschelde. Mud erosion is also observed in areas that shifted from marsh to intertidal flat.