ANALYZING ORGANIC CARBON AND PARTICLE SIZE IN SEDIMENT DEPOSITED BY THE MISSISSIPPI RIVER FLOOD OF 2019

Large areas of the Mississippi River Delta are disappearing due to eustatic sea-level rise, coastal subsidence rates, erosion, and mismanagement of sediment resources. For decades, the Mississippi River has been restricted by man-made levees; this has impeded the sediment supply to coastal wetlands and resulted in the loss of large volumes of sediment to the Gulf of Mexico. During spring floods, the Mississippi River transports large volumes of mineral and organic sediment which could be used to rebuild land and protect the people and the natural resources of the delta; current plans for restoring the Mississippi River Delta include leveraging the sediment mobilized during floods, by diverting floodwaters to locations that have subsided below mean sea-level.

During the 2019 spring flood on the Mississippi River, the Bonnet Carre Spillway was opened to divert flood waters away from the city of New Orleans and to Lake Pontchartrain. The flood deposited a significant volume of sediment in the spillway and lake, providing an opportunity to study sedimentation patterns in an engineered diversion and to collect data needed to inform coastal restoration efforts that incorporate sediment diversions. In this work, we focus on describing the deposits in the spillway and lake, and on quantifying the relative contributions of mineral and organic sediment and the particle sizes associated with each.