Evaluating the hydrodynamic and transport responses to storm surge barriers in a partially mixed Estuary: A case study of the Hudson–Raritan estuary

Abstract

Storm surge barriers (SSB), as engineering measures within broader coastal risk mitigation strategies, have been implemented or proposed in estuaries around the world. During non-storm periods, some parts of barriers restrict cross-flow area which alters water exchange and estuarine hydrodynamics. This study investigates the effects of permanent barrier infrastructure on the hydrodynamics of the Hudson-Raritan Estuary (HRE), a partially mixed estuary characterized by a complex geometry that includes bays connected by tidal straits and multiple tidal inlets. Our research employs a three-dimensional hydrodynamic model (EFDC) to focus on five distinct scenarios developed by the United States Army Corps of Engineers (USACE), exploring aspects of these systems that have not been examined previously. The implementation of SSBs leads to increased salinity content, intrusion, and stratification in tributaries and a decrease on the landward side of the barrier, particularly when key pathways for water exchange are obstructed. Depending on the specific configurations of the SSBs, salinity variations in different regions range from an increase of 12 % to a decrease of 10 %. Results indicate a reduction in both semi-diurnal and diurnal tidal signals across the HRE, significantly affecting the energy partitioning. For instance, an SSB at the Lower Bay entrance reduces the semi-diurnal component of the total energy budget from 73 % in the base case to 46 %, while increasing the subtidal component's contribution from 23 % to 50 %. Additionally, SSBs alter the residual currents, induce eddy formations, and amplify currents across both surface and bottom layers. The response of residence times to SSB configurations varies spatially across the domain; on average, residence time in the HRE rises between 13 % and 67 % across the different SSB configuration scenarios compared to the base case, which has a spatially averaged residence time of approximately 15.9 days. The impact of SSBs on estuarine hydrodynamics strongly depends on their specific location and configuration. This study provides a framework for understanding the potential impacts of any proposed surge barrier systems and enhances our comprehension of their ecological and environmental effects.