Long-term salt marsh vertical accretion in a tidal bay with reduced sediment supply

• Published in: Estuarine, coastal and shelf science Vol. 146; pp. 14 - 23
• Main Authors: Ma, Zhigang, Ysebaert, Tom, van der Wal, Daphne, de Jong, Dick J., Li, Xiuzhen, Herman, Peter M.J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 05-06-2014; Elsevier
• Subjects: accretion; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish water ecosystems; Channels; Estuaries; Flooding; Fundamental and applied biological sciences. Psychology; IMARES Regiostation Yerseke; Marine; Marshes; Oosterschelde; Regiocentrum Yerseke; Regional center Yerseke; salt marsh; Salt marshes; sediment supply; Sediments; Storms; Synecology; Trends; Netherlands; Europe; Western Europe; ANE, Netherlands, Zeeland, Oosterschelde; ANE, Netherlands; accretion; sediment supply; Oosterschelde; salt marsh; Vertical; Salt marsh; Brackish water environment; Accretion; Bay; Sediments; Long term; Tides
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2014.05.001

Because of damming and intensive human activities, the sediment supply to many estuaries and deltas is dramatically decreasing. In the Oosterschelde (southwest Netherlands), a storm surge barrier (SSB) and two compartmentalization dams were built in the 1980s to protect the densely inhabited inland against flooding. After these constructions, the tidal range and mean high water level in the Oosterschelde decreased by about 12% and suspended sediment concentrations in the channels dropped by 52–70% compared to the pre-barrier conditions. The vertical accretion rates of the three largest salt marshes (Rattekaai, Sint Annaland and Slaak) in the Oosterschelde in response to this decreased sediment supply were investigated. There was a general accreting trend over the entire post-barrier period (1988–2011) in all three marshes. The predicted slowdown in accretion rates by De Jong et al. (1994) did not persist, although accretion rates were lower than in the pre-barrier period. More than 20 year observations from kaoline markers showed variation of accretion rates within and among marshes. Year-to-year variation in accretion rates was large, but only weakly (not significantly) related to the duration and frequency of marsh overflow and over-marsh extreme flooding events. However, storm events are hypothesized to be responsible for the observed trends, but our observations lack the temporal resolution to identify specific storm events. Salt marshes in the Oosterschelde are expected to survive under the present sea level rise rate and subsidence rate scenarios.