Examining hydrodynamics and connectivity resulting from atmospheric frontal passages in a coastal river delta

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This project aims to understand how cold fronts affect water movement in coastal river deltas. In regions with small tides, such as coastal Louisiana, winds associated with cold fronts are known to be important for circulating water and sediment throughout the region. However, scientists do not understand how water in complex coastal regions, such as coastal river deltas, respond to winds associated with cold fronts. Understanding this interaction is important, because cold fronts may contribute to coastal erosion, a major issue in Louisiana, and restoration efforts must account for the effects of cold fronts to be effective. This project will investigate these issues throughout coastal Louisiana using field measurements and modeling of wind events and water movement. In addition to improving the understanding of water circulation in complex coastal regions, the project will also engage stakeholders and delivers hands-on demonstrations to Baton Rouge (Louisiana) schoolchildren. Atmospheric cold fronts are major drivers of water circulation and sediment transport in coastal Louisiana, a region experiencing rapid land loss due to relative sea level rise, coastal erosion, and lack of sediment input. There is considerable interest in understanding and using natural deltaic processes through sediment diversions to mitigate land loss, as well as increased storm surge and saline intrusion. River deltas comprise relatively deep distributary channels and shallow wetlands that are hydraulically connected to channels. Previous analyses of the hydrodynamics resulting from frontal passages have focused on relatively homogeneous environments that do not have considerable changes in depth (e.g., the coastal shelf or open bays). Stark changes in depth, spatial gradients in connectivity, and the impact of fluvial versus marine forcings make river deltas a significantly more complex heterogeneous environment where cold front-induced circulation is not yet understood. This proposal will: 1) determine how water levels vary throughout frontal passages across the Mississippi Delta Region, 2) determine how appreciable changes in depth across a heterogenous delta affect hydrodynamics induced by cold fronts, and 3) identify the mechanisms that control channel-wetland connectivity in deltas during cold fronts. Synoptic analyses will focus on the coastal Louisiana region while detailed field measurements and numerical modeling will focus on the Wax Lake Delta in Louisiana. Outreach efforts include digital brochures distributed to local stakeholders and coastal managers, as well as a portable wind-driven wave tank that will be used in demonstrations engaging 200 undergraduate students and 2,500 K-8 students and teachers on an annual basis. This proposal is co-funded by the Hydrologic Sciences and Physical Oceanography programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.