Title

Short-term assessment of morphological change on five lower mississippi river islands

Abstract

Abstract To examine short-term morphological changes and variables controlling this change, we conducted a study on five lower Mississippi River islands in 2007 and 2008. The southernmost island was located 25 km north of Memphis, TN, and the northernmost island was located 105 km north of Memphis. We surveyed elevations along six transects for each of the five islands to examine morphological changes between years and measured river velocity and backscatter intensity (sediment load) at the head, middle, toe, zee, and fore sides of the islands. We predicted the impacts of flooding on island geomorphology would be greatest at the head (upstream edge) and fore (thalweg) side. In addition, we predicted the morphology of islands present in the main channel in the 1890s would differ in morphology from contemporary islands. Results indicated morphological change during the study period but only in width. Islands showed general lateral migration, with one side aggrading while the other side eroded. Changes in morphological characteristics were consistent with intensity of river flow around the islands, with the highest velocity and sediment load observed near the island head and to a lesser degree the thalweg side of islands. In reference to islands present in the late 1890s, contemporary islands appear to be more elongated and have a greater surface slope. Since these islands provide beneficial habitat for flora and fauna, it is crucial to understand the dynamic nature of these landscape features.

Publication Title

Southeastern Naturalist

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