Assessing Effects of Sea Level Rise on Plum Island Estuary Marshes Using the Hydro-MEM Model.

Studies show that coastal estuaries and marsh systems are at the risk of losing their productivity under increasing rates of sea level rise (SLR) (Warren and Niering, 1993; Donnelly and Bertness, 2001). A rise in relative sea level may increase flooding across the marsh surface and thereby increase the hydroperiod and re-establish the elevation of the marsh relative to the new mean sea level (Morris, 2006). Linking hydroperiod to the spatial biomass distribution of marsh vegetation has been the focus of many studies (Wiegert et al., 1990, Morris et al., 2002, Doyle et al., 2007, Friedrichs, 2011, Belliard et al., 2016 and Alizad et al., 2016). This research examines how marsh elevation determines the frequency and duration of tidal flooding (hydroperiod), which is one of the most effective parameters for the formation and regulation of marsh growth (Morris et al. 2002 and Fagherazzi et al., 2012). A method to estimate hydroperiod across the marsh surface was developed and included in the coupled Hydro-MEM model (Hagen et al., 2013 & Alizad et al., 2016) to compute biomass density. The updated Hydro-MEM model was applied across the Plum Island Estuary in Massachusetts to assess the effects of SLR scenarios (Parris et al., 2012) on salt marsh productivity for the year 2100. This analysis shows an increase in salt marsh productivity for low rates of SLR and lower productivity under the higher SLR scenario. The study also demonstrates the potential for marsh loss and upland migration under higher rates of SLR.