INFLUENCE OF SALINITY WEDGE ON FLOW AND SEDIMENT DIVERSION THROUGH A COMPLEX DELTAIC SYSTEM

Abstract

The Bird’s Foot Delta (BFD) is located at the confluence of the Mississippi River and the Gulf of Mexico in southeast Louisiana, USA. It is a 521,000-acre delta located around the three main distributaries (Southwest Pass, South Pass, and Pass-a-Loutre) off the terminal end (Head of Passes) of the Mississippi River. Here, the delta is a highly productive ecosystem that serves as a refuge for migratory birds, harbors fisheries, and acts as defense mechanism against storm surge for the city of New Orleans. Over the past several decades, the wetlands of the eastern BFD have experienced severe degradation. The primary cause of wetland loss in this area is the combination of relative sea level rise (RSLR) and decreased hydrologic connection to the Mississippi River, which results in insufficient sediment deposition and increased salinity. The BFD restoration project proposes to restore the hydrology and improve the freshwater and sediment delivery to the Eastern Bird’s Foot Delta through dredging some combination of the three largest distributaries south of Head of Passes (HOP). To inform restoration efforts, Mott MacDonald (MM) performed extensive modeling efforts to evaluate the influence of salt wedge on hydraulic and morphological patterns across the BFD.