Rising sea level can cause an increase in surface runoff from coastal areas by raising the watertable and thus increasing the incidence of saturated soil conditions in low-lying areas. As surface runoff increases, less rainfall will infiltrate into the ground and groundwater discharge to the coast will decrease. The link between sea level rise and runoff is critically dependent on the sensitivity of surface runoff to changes in the elevation of the watertable. A significant relation between the two is demonstrated for a coastal watershed on Cape Cod, where it is estimated that a 10 cm rise in the watertable will increase surface runoff by 70% and decrease groundwater discharge by 20%. Effects on near-shore ecosystems include changes in nutrient fluxes and in the salinity of the sediments.