CSDMS 2014 annual meeting poster Ehab Meselhe
Sediment Dynamics of the Lower Mississippi River: Understanding Sediment Availability and Delivery for Land Building
Abstract:
There is a dire need to use sediment from alluvial rivers to sustain and create new marsh, sustain barrier islands and ridges. Coastal Louisiana is a prime example where wetland loss rates are one of the highest worldwide. This presentation discusses the sediment dynamics of the Lower Mississippi River, specifically the sediment availability, temporal and spatial variability, as well as the sediment size characteristics. The investigation is performed using morphodynamic numerical tool (Delft3D). The Louisiana 2012 State Master Plan identified two viable mechanisms to build land, sediment diversions and dedicated dredging. The morphodynamic model has been parameterized and validated using historical and recent field observations. The model is being used to investigate the riverside morphological response to single or multiple dredging of lateral sand bars as well as the infilling pattern and rate. The model will also be used to identify the key design parameters that govern the sediment capture efficiency of sediment diversions, e.g. the alignment angle, invert elevation, diversion size, and location.
The uncertainty and limitations in the ability of the numerical model to adequately capture the relevant physical processes is discussed. The implications of such limitations on the decision making process is presented. Despite the limitations and uncertainties, the analysis provides valuable design recommendation for sediment diversions to maximize their sediment capture efficiency. The analysis also provides a management plan for dredging multiple borrow areas. The management plan includes coordination of dredging timeline among multiple borrow pits, as well as coordination between dredging activities and sediment diversion operation plans.
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