Simulated Saltwater Intrusion in the Overburden with 8 ft of Sea Level Rise

Groundwater modeling was used to simulate the effects of sea-level rise on groundwater levels in the New Hampshire Seacoast. The MODFLOW-USG Transport model (Panday, 2022) was used to simulate groundwater flow and saltwater intrusion in these communities. This map shows relative salinity (0=freshwater-blue,1=saltwater-red). SWI was simulated for Rollinsford, Dover, Madbury, Durham, Newmarket, Newfields, Exeter, Newington, Portsmouth, New Castle, and parts of Rye and Stratham. SWI was not simulated in the southern portion of the NH Seacoast, including parts of Rye and Stratham, Greenland, North Hampton, Hampton, Hampton Falls, and Seabrook. The SWI modeling produced estimates of relative salinity in groundwater at various depths ranging from approximately 10 feet to more than 800 feet. This map shows SWI in the overburden with 8 feet of SLR. There is substantial uncertainty in these estimates due to limited knowledge of bedrock fracturing and other subsurface parameters. These model results and maps provide a first-cut estimate of saltwater intrusion and should be enhanced and/or verified by field measurements.