Location: Watershed Physical Processes ResearchTitle: Relationship of point bar morphology to channel curvature and planform evolution
|ROWLEY, TAYLOR - Louisiana State University|
|KONSOER, KORY - Louisiana State University|
|LI, ZHI - University Of Illinois|
|Ursic, Michael - Mick|
|GARCIA, MARCELO - University Of Illinois|
Submitted to: Geomorphology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2020
Publication Date: 2/15/2021
Citation: Rowley, T., Konsoer, K., Langendoen, E.J., Li, Z., Ursic, M.E., Garcia, M. 2021. Relationship of point bar morphology to channel curvature and planform evolution. Geomorphology. 375:107541. https://doi.org/10.1016/j.geomorph.2020.107541.
Interpretive Summary: The understanding of the migration of river meander bends is incomplete because of highly complicated flow and sediment transport patterns, and resulting interactions between vertical and planform adjustment. Planform is typically represented by the curvature of the channel centerline, while point bars are the prominent features comprising the river bed. Combining analysis of aerial imagery and river bathymetry collected using unmanned aircraft systems and multibeam sonar, ARS scientists in Oxford, MS, in collaboration with researchers from Louisiana State University and the University of Illinois developed relationships between channel centerline curvature and point bar geometry for select meander bends on the Wabash River, IL/IN, and the Pearl River, MS/LA. Additionally, an analytical model to estimate river bed geometry from channel centerline curvature was used to investigate the developed relationships. The temporal adjustment of planform and point bar geometry on both river systems was consistent for meander bends migrating in downstream direction. Specifically, the point bars presented a flat upper geometry, maximum migration rates occurred near the bend apex, and the bends developed a curvature comprising multiple maxima. These findings can be used in river engineering to determine rate and direction of future meander bend migration. Action agencies will therefore be able to prioritize bank stabilization to protect farmland along meandering rivers.
Technical Abstract: Point bars are prominent features in meandering rivers, yet our understanding of the complex interactions among the morphology of the point bars to channel planform and curvature remains incomplete. Thus, this study uses high-resolution field investigation techniques, including multibeam sonar and structure-from-motion, to characterize point bar morphology on twelve point bars within two river systems; the Pearl and Wabash Rivers. Estimates of channel curvature are compared to channel and point bar characteristics including width, migration rate, centerline longitudinal bed elevation, transverse bed slope, and a shape factor. Results reveal that the Pearl River reach has abundant and a systematic distribution of bilinear transverse bar profiles relative to the Wabash River. Additionally, field data are compared to synthetic data generated from PyRiverBed, a centerline-driven bed evolution model. The synthetic data captures a reasonable morphology, yet the model is incapable of capturing local variations in bar morphology that arise as a result of changes in channel width and curvature.