Quantitative Description of Dune Scales and Their Longitudinal Variation in the Lower Missouri River Using Single Beam Sonar Data

Quantitative descriptions of dune geometric scales such as length and height are important for roughness characterization and navigation safety assessments on large sand-bedded rivers. This study reports the results of quantitative analysis of dune scales applied to single beam sonar data on the Missouri River. Sonar data were obtained by the US Army Corps of Engineers along the sailing line of the lower Missouri River for an approximately 35-mile reach located near the junction with the Osage River tributary. The sonar data were collected on three dates in April, May, and June of 2021. These data were analyzed using multiple automated dune scale characterization algorithms to extract the height, length, and longitudinal location (e.g., river mile) for individual dunes. Results show relatively similar mean values of dune geometric scales for April and May and larger magnitude dune scales for the June dataset, which was obtained at higher discharge conditions. Longitudinal variations in local mean dune scales along the sailing line were also assessed for the June dataset. Plots of dune length/height versus river mile show regions with smaller magnitudes and interspersed sections with local peaks in the dune scale magnitude. The moving average of three adjacent dunes (in the streamwise direction) was calculated and demonstrated that local mean scales ranged from 5 to 85 m for the dune length and from 0.4 to 3.1 m for the dune height. This work will support future modeling, monitoring, and management efforts on the Missouri River.