Morphologic adjustments of actively evolving highly curved neck cutoffs. Issue 4 (9th December 2019)

• Record Type: Journal Article
• Authors: Richards, Derek; Konsoer, Kory
• Is Part Of: Earth surface processes and landforms. Volume 45:Issue 4(2020)
• Page Start: 1067
• Page End: 1081
• Publication Date: 2019-12-09
• Subjects: neck cutoffs -- meandering rivers -- channel morphology -- difference mapping; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4763
• Languages: English
• ISSNs: 0197-9337

Abstract

ABSTRACT: Neck cutoffs and their resultant oxbow lakes are important and prominent features of riverine landscapes. Detailed field‐based research focusing on the morphologic evolution of neck cutoffs is currently insufficient to fully characterize cutoff evolution. High‐resolution bathymetric data were collected over 3 years for the purpose of determining channel morphology and morphologic change on three actively evolving neck cutoffs. Results indicate the following general trends in morphologic adjustment: (1) a longitudinal bar in the upstream meander limb that develops near the entrance to the abandoned bend; (2) a deep scour hole in the downstream meander limb immediately downstream of the cutoff channel; (3) erosion of the bank opposite the cutoff in the downstream meander limb; (4) a cutoff bar in the downstream meander limb at the junction corner of the cutoff channel and the downstream meander limb; and (5) perching of the exit of the abandoned bend above the cutoff channel due to channel bed incision. The results presented herein were used to develop a conceptual model that depicts the morphologic evolution of highly curving neck cutoffs. The findings of this research are combined with recent analyses of the three‐dimensional flow structure through neck cutoffs to provide a mechanistic explanation for the morphodynamics of neck cutoffs. © 2019 John Wiley & Sons, Ltd. Abstract : This study focuses on morphologic changes following neck cutoffs on meandering rivers when the cutoff channel is not straight but highly curving. Investigation of three neck cutoffs on the White River in Arkansas reveals key similarities in the morphologic evolution that are summarized with a conceptual model. The model depicts the stages following cutoff initiation prior to plugging, with the development of a pronounced cutoff bar, erosion of the bank opposite the cutoff, and downstream rotation of the resulting bend.