The relationship of channel planform and point bar architecture on a reach of the Wabash River near Grayville, Illinois

Authors: ROWLEY, TAYLOR - Louisiana State University; KONSOER, KORY - Louisiana State University; Ursic, Michael - Mick; Langendoen, Eddy

Submitted to: Joint Federal Interagency Sedimentation and Hydrologic Modeling
Publication Type: Proceedings
Publication Acceptance Date: 4/30/2019
Publication Date: 6/24/2019
Citation: Rowley, T., Konsoer, K.M., Ursic, M.E., Langendoen, E.J. 2019. The relationship of channel planform and point bar architecture on a reach of the Wabash River near Grayville, Illinois. In Proc. 4th Joint Federal Interagency Sedimentation and Hydrologic Modeling. June 24-28, 2019, Reno, NV, 5 pp.

Interpretive Summary: The understanding of the migration of river meander bends is incomplete because of highly complicated flow and sediment transport patterns. However, the stratigraphic record of the point bar located along the inner bank of a meander bend could provide insight on the historic migration of a bend and therefore controlling processes. Using a combination of airborne lidar and ground penetrating radar (GPR), ARS scientists in Oxford, MS, in collaboration with researchers from Louisiana State University measured the internal sedimentary structure of point bars, deposited between 2011 and 2017, on two meander bends on the Wabash River, IL/IN, with very different planform geometry. The GPR data reflected well the differences in the style of evolution between the point bars. Findings from this study help characterize and relate the style of planform evolution to point bar architecture. These findings can then be used in river engineering to determine rate and direction of future meander bend migration.

Technical Abstract: The erosional and depositional characteristics of meandering rivers lead to the formation and maintenance of point bars along the inner banks of meander bends. Point bars are composed of sediment layers in patterns resulting from the rate and style of channel migration, hydrodynamics, and sediment transport and deposition within the river system. The distribution of the sediments preserved in the internal architecture of a river point bar provides a record of channel planform evolution. Geophysical methods are used to gain a large-scale visualization of the subsurface and aid in the interpretation of historic channel patterns. Comparing known surficial extents of the point bar to features identified in the subsurface can also enhance the understanding of historic channel planform. This study investigates two point bars along bends with different styles of migration, Maier and TB3, in a well-documented reach of the Wabash River near Grayville, IL. Evidence from historic aerial photography, modern lidar, multibeam echo sounder (MBES), photogrammetry, and geophysical surveys were used to determine the relationship between the point bar architecture and channel planform. Airborne lidar was flow in 2011 and is used to create the 2011 point bar surface. In 2017 a terrestrial lidar and Real Time Kinematic-Global Navigation Satellite System (RTK-GNSS) topographic survey are combined to create the surface for TB3. In 2018, a photogrammetric survey collected with a small unmanned aerial system (sUAS) is used to create a structure-from motion derived surface for Maier bend. The 2018 survey-based point bar surfaces are differences from the 2011 point bar surfaces to get a Digital Elevation Model (DEM) of difference (DoD) to visualize areas of erosion and deposition. Geophysical surveys using ground penetrating radar (GPR) were conducted in transverse and streamwise lines across the point bars in 2018. Elevation profiles from the 2011 point bar surfaces are extracted and overlain onto the 2018 GPR images to determine how the point bar is preserving the structure of sediments previously deposited. Results from this study provide an update to current models of point bar architecture.