Hydrodynamics and Sediment Dynamics in a Receiving Basin for Sediment Diversion: a Case Study in Barataria Bay, Louisiana, USA

Barataria Bay is a receiving basin of Mid-Barataria Sediment Diversion in Louisiana, USA. In this region the data of sediment transport and hydrodynamics are scarce but important for the design and planning of sediment diversion to be implemented in near future. Four-months bottom boundary layer observation was conducted to study winter and spring hydrodynamics and sediment dynamics in the bay. Hourly waves, tides, currents and bottom suspended sediment concentration were measured using multiple optical and acoustic sensors attached to two tripod platforms. High-temporal resolution data indicated that during winter, salinity at northern bay was mainly controlled by northerly wind during cold fronts, and tidal currents kept southern bay salinity high during the same period. In spring, frequent pervasive southerly winds and the westward shelf transport of flooding freshwater from Southwest Pass of Mississippi River Delta lowered the salinity in southern bay. Density spectral analysis showed that wind-driven currents played the most important role in generating wave-current combined shear stress that triggered bottom sediment resuspension. Style-Glenn 1-D boundary layer model was also applied for sediment flux calculation. During the cold front passages sediment transport directions generally rotated and its magnitudes changed greatly when southeasterly wind shifted to intensified northwesterly wind. Southerly pre-front winds facilitated wetland sedimentation by transporting sediment to the northern bay during high water level conditions such as flooding spring tides. Conversely, northerly winds during cold fronts could dominate over bidirectional tidal currents and led to southward net sediment transport and eventual sediment loss in the bay. Timing of diversion openings, orientation of receiving basins, dominant wind directions and water levels should be considered in the planning and management of future sediment diversions in coastal areas