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Salt Marsh Response to Increased Tidal Inundation
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  • Brian Yellen,
  • Jonathan Woodruff,
  • Hannah Baranes,
  • W. Rockwell Geyer,
  • Simon Engelhart,
  • Frances Griswold
Brian Yellen
University of Massachusetts Amherst

Corresponding Author:byellen@umass.edu

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Jonathan Woodruff
University of Massachusetts Amherst
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Hannah Baranes
Gulf of Maine Research Institute
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W. Rockwell Geyer
Woods Hole Oceanographic Inst.
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Simon Engelhart
Durham University
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Frances Griswold
University of Massachusetts Amherst
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Barrier inlets and marshes behind them are often viewed and managed as separate systems with independent controls because they are affected by different boundary conditions. Here, we make use of a 120-year-old storm-driven change in inlet location to illustrate how barrier beaches and wetland processes are intricately linked. Further, we show that tidal marshes can be resilient to a rapid increase in inundation given sufficient sediment supply and discuss implications for coastal management along sediment-deficient coastlines. In 1898, a coastal storm eroded a new inlet through the barrier beach that fronts the North-South Rivers Estuary in Massachusetts, USA. The old inlet silted in after the storm, and the change in inlet location shortened the North River channel by 5.6 km. After the inlet location change, historical records indicated increased high tide levels along the North River. We make use of this increase in water levels and associated marsh response to examine conditions that have allowed for marsh resilience after a rapid increase in inundation depth. Sediment cores show that increased mineral sediment deposition after 1898 played a dominant role in allowing marshes along the North River channel to adjust to greater inundation. To accommodate greater tidal flow after the change in inlet location, the North River channel widened by an average of 18%. Edge erosion from channel widening likely provided sediment to the marsh platform. Modern water level monitoring along the channel shows that mean high water declines landward by at 4.8 cm/km up to 10 km from the inlet. North River channel shortening thereby likely increased mean high water by at least 27 cm within the lower estuary. At present, the marsh platform elevation along both channels has largely reequilibrated to the effective change in sea level, with similar marsh inundation depths along both channels of the estuary. The role of mineral sediment in allowing for rapid marsh sediment deposition and resilience of this marsh to an abrupt increase in inundation depth points to the importance of management strategies that maintain sediment supplies to coastal regions.