Spatial variations in sediment transport through neck cutoffs

Authors: Derek Richards*, Louisiana State University, Kory Konsoer, Louisiana State University
Topics: Geomorphology
Keywords: Neck cutoffs, sediment transport, morphology, multibeam echo sounder
Session Type: Paper
Day: 4/12/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Balcony K, Marriott, River Tower Elevators, 4th Floor
Presentation File: No File Uploaded

Meander cutoffs are a common feature in riverine landscapes, yet due to their intermittent occurrence, detailed process-based geomorphic investigations during actively evolving neck cutoffs have been limited. However, five different neck cutoffs on the White River in central Arkansas have provided an opportunity to study the morphodynamics of neck cutoffs during the transition from active cutoff to bend abandonment and oxbow lake formation. In this paper, the spatial patterns of sediment transport and channel bed composition within the cutoff channels and entrance/exit of the abandoning loop are examined and linked to the morphodynamic evolution of the river. High-resolution bathymetric data were collected using a multibeam echo sounder (MBES) in May 2016 at the five different cutoff sites. During a large flood, in May 2017, multiple MBES surveys were conducted daily at three of the five sites, which included repeat surveys after 4 hours for the purpose of evaluating dune celerity. From these surveys, the spatial pattern of erosion and deposition were determined for annual, daily, and hourly timescales, and provide insights into bar development, dune migration, and sediment transport rates in actively evolving neck cutoffs. Additionally, bank and bar sediment samples and cores were collected during low flow stages to analyze depositional patterns and overall sediment characteristics of these neck cutoffs and their developing oxbow lakes.

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