Geomorphic and anthropogenic influences on hydrologic connectivity along the lower Mississippi River




Sounny-Slitine, Moulay Mohamed Anwar Adounia

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This thesis examines geomorphic and anthropogenic factors in natural levee construction and presents a new digital elevation model extraction method for delineating natural levees. The method is applied to the lower Mississippi River to interpolate the elevation profile of the western natural levee. The resulting levee profile uncovers the complex nature of the bankfull stage level, which varies spatially along the length of the river in elevation. This profile is compared to human modifications of the river to show the morphology of the natural levee. While the levee may initially develop at a quick rate, the acceleration of growth slows over time due to lower stage-duration intervals. This leads to depressed levee systems and lower bankfull stage levels at sections of the river. These stages are used to model longitudinal hydrological connectivity between the river's main channel and the adjacent floodplain. High magnitudes of connectivity of 87% inundation occur with a 10% probability. These inundation models highlight the increased interaction that takes place between the river and its floodplain. It can be concluded that the modifications of the river’s channel in the form of cut-offs and revetments led to immature natural levees embanking the river, which are more prone to overbank processes and increase the frequency of inundation of the floodplain. This finding has significance to riparian conservation, planning, and engineering design, highlighting the lingering impacts of river engineering projects through increased hydrological connectivity.



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