Planform Evolution Of Neck Cutoffs On Elongate Meander Loops, White River, Arkansas, Usa

During the formation of a neck cutoff on a compound elongate loop, the upstream and downstream limbs can become oriented roughly subparallel with flow in opposite directions separated by a narrow meander neck. Immediately following cutoff of this thin neck, flow from the upstream limb is sharply redirected into the downstream limb over a short distance, leading to complex patterns of three-dimensional velocities that have implications for the evolution of the cutoff channel and the transformation of the abandoned bend into an oxbow lake. This paper investigates the process dynamics and planform evolution of neck cutoff and oxbow lake formation using measurements of flow velocities and time-series analysis of aerial photography for three neck cutoffs along the White River, Arkansas (USA) - each representing a different stage in the morphologic evolution from cutoff to oxbow lake. Results from this study suggest that the planform geometry of neck cutoff on an elongate meander loop can influence the spatial patterns of sediment erosion and deposition within the abandoned loop leading to increased hydrologic connectivity to the main channel, and contribute to the overall morphodynamics of highly sinuous meandering rivers.