Morphologic and Ecologic Analysis of a Proposed Network of Mississippi River Sediment Diversions
Ehab A Meselhe1, Melissa Millman Baustian2, Kazi M Sadid2, Fei Xing2, Katelyn Costanza2, Mead A Allison3, Elizabeth Jarrell4, Carol Parsons Richards4 and James Pahl4, (1)Water Institute of the Gulf, Baton Rouge, LA, United States, (2)The Water Institute of the Gulf, Baton Rouge, LA, United States, (3)Tulane University of Louisiana, New Orleans, LA, United States, (4)Coastal Protection and Restoration Authority, Baton Rouge, LA, United States
Abstract:
Deltaic processes are governed by factors that include the characteristics of inflowing sediment (e.g., temporal variability of the load and size class distribution), receiving basin geometry and hydrodynamic condition (e.g., water depth, tidal range, circulation pattern, and wind field), substrate character (e.g., sediment type and soil strength), and ecological processes (e.g., vegetation dynamics). These factors influence the deltaic growth pattern as well as the size and timing of channel bifurcations. This topic is of importance to deltas experiencing land loss today due to factors such as subsidence and sea level rise. The Mississippi River Delta is an example where sediment diversions are being considered in conjunction with other restoration actions to minimize loss of wetlands. Historically, the Mississippi River has played provided sediments, nutrients, and fresh water to support Louisiana’s coastal wetland system. Field observations coupled with numerical modeling at various temporal and spatial scales, has provided insights toward a system-scale approach to design, evaluate and operate sediment diversions. These research activities investigate the uncertainties associated with morphological and ecological processes both on the river and receiving basin sides and identify parameters influencing the magnitude and rate of building new land and sustaining existing wetland areas. Specifically, this presentation discusses the impact of extracting sediment and water from rivers and the ability to convey (and retain) sediment to the receiving basins. In addition to delivering sediment to receiving basins, some proposed sediment diversions will discharge high volumes of nutrient-rich fresh water into existing wetlands and bays. A goal of the analysis presented here is to improve our understanding of morphological responses of the receiving basins and the ecological effects of discharging freshwater and nutrients at this scale.
