Understanding Dynamics of Groundwater Flows in the Mississippi River Delta

•Complex hydrogeological setting in the Mississippi River Delta is revealed.•Groundwater flow rate is 3 to 4 orders smaller than Mississippi River discharge rate.•Groundwater and surface water interacts actively during severe hydrologic events.•Sharp groundwater recharge-to-discharge reversion occurs right after hurricanes pass.•High pore water pressure during and after hurricanes may destabilize surficial sediments.