The Movement of Storm Surge Through a Surficial Aquifer

This study investigates the movement of storm surge through a sandy unconfined aquifer to answer the question: What is the role of tropical system storm surge in the salinization/freshening of surficial aquifers? To answer this question several methods were used. Geologic cross sections were created from approximately 150 boring logs in Harrison County, Mississippi. The cross sections were used to generate a conceptual model and a hydrogeologic model of a beach-barrier island site. Simple sea level and storm surge models were developed using a digital elevation model in Surfer to determine the extent of flooding for a variety of surge/sea level rise scenarios. The surge and sea level rise models were used to evaluate the extent of land inundation at 1 meter increments. Field data were collected from wells in Gulfport, Mississippi from 2006-2009 to evaluate residual impacts of Hurricane Katrina and investigate impacts of systems that moved through the region during the sampling period. Field study and computer modeling results indicate that the impact of tropical systems on surficial aquifer salinity is minimal because of the large precipitation component associated with storms and short lived because of the high hydraulic conductivity associated with sandy surficial aquifers. Storm surge is reduced in salinity relative to sea water because of the large amount of precipitation and runoff associated with the storm. The surge has reduced ability to infiltrate the groundwater system because the ground is already saturated by precipitation that precedes the storm. The saline water moves rapidly through the unconfined aquifer because of the short flow paths and high hydraulic conductivity