CSDMS 2016 annual meeting poster GiulioMariotti
Revisiting salt marsh resilience to sea level rise: Are ponds responsible for permanent land loss?
Abstract:
Ponds are un-vegetated rounded depressions commonly present on marsh platforms. In order to study how ponds affect the long-term morphological evolution of tidal marshes I implemented a simple model for pond vertical and planform dynamics. Even if the vegetated platform keeps pace with Relative Sea Level Rise (RSLR), episodic disturbances of the marsh vegetation cause the formation of small (1-10 m) ponds. Isolated ponds deepen and enlarge because of biochemical processes that prevent vegetation growth and decompose the existing organic sediment. Ponds eventually connect to the channel network and re-establish a biochemistry conducive for vegetation growth. Recovery occurs if, at the time of drainage, the pond lies above the limit for vegetation growth, or if the inorganic deposition rate is larger than the rate of RSLR. If ponds cannot recover they will enlarge and eventually enter the runaway erosion by wave edge retreat. A large tidal range, a large sediment supply, and a low rate of RSLR favor pond recovery. The model suggests that inorganic sediment deposition alone controls pond recovery, even in marshes where organic matter dominates accretion of the vegetated platform. Because permanent loss by pond expansion can occur even if the vegetated platform keeps pace with RSLR, I conclude that marsh resilience to RSLR is less than previously quantified and that increasing the availability of inorganic sediment is necessary to sustain high rates of RSLR.
* Please acknowledge the original contributors when you are using this material. If there are any copyright issues, please let us know and we will respond as soon as possible.
