SEDIMENTATION PATTERNS AND DEPOSITION IN THE PROGRADING WAX LAKE DELTA

The Mississippi River has been dammed and levied since the 1950s to control the river from flooding and support navigation and commerce. Sediments delievered to the Lousisiana delta plain have decreased by half since the major projects of the 1950’s. Despite significant reductions in sediment load, the Wax Lake Delta is forming at the mouth of a man made dredged channel that flows off of the Atchafalaya River, which is the principal distributary of the Mississippi River. The remaining sediments carried by the Mississippi River are essential in the building of delta wetlands and helping to reverse coastal wetland loss. This study analyzes pre- and post-elevation data from 2008 and 2009 to understand the amount of elevation gain and sediment deposition associated with large river floods. Mean wetland elevation gain during the floods of 2008 and 2009 was 3.9 cm and 2.2 cm, respectively. Using soil bulk properties and mean elevation gain, I estimated that 2.3x10⁶ Mt and 1.2x10⁶Mt of sediment was deposited in the Wax Lake Delta wetlands for 2008 and 2009, respectively. If the total annual load of sediments in the Atchafalaya River is approximately 50Mt yr-1, we can estimate that <10% of the total available sediment load is deposited in the wetlands, just during spring flood events. This study provides good first order estimates of sediment deposition that can contribute to future research and understanding of the Wax Lake Delta formation and maintenance.