Abstract
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.