Influence of Coastal Flooding on Seawater Intrusion in Coastal Aquifers

Coastal aquifers as vital fresh groundwater resources are subjected to coastal flooding due to storm surge and sea-level rise (SLR). Increasing the seawater intrusion volume (SWIV) from both seaward boundary and land-surface can be expected in coastal aquifers as a result of coastal flooding. In the present study, a numerical method using a saturated-unsaturated density-dependent flow and transport code, SUTRA, is employed to understand how such effects can change the groundwater quality of unconfined aquifers. Storm surge simulation shows that SWIV is increased during the coastal storm below the flooded land-surface. However, this increase is a short-term event. Also, existence of topographic depression negligibly enhances the SWIV in comparison with that of no topographic depression. Unconfined aquifers are significantly influenced from SLR as a long-term effect. Raising sea level and occurrence of a coastal storm causes that even an area much farther inland would be at risk of being flooded.