Bedform Morphodynamics in a Meandering Stream

Thursday, 18 December 2014
Margaret L Palmsten1, Jessica L Kozarek2, Ali Khosronejad2 and Joseph Calantoni3, (1)Naval Research Lab Stennis Space Center, Stennis Space Center, MS, United States, (2)University of Minnesota, Minneapolis, MN, United States, (3)Naval Research Laboratory, Stennis Space Center, MS, United States
Bedforms and sediment transport were observed in a sandy meander bend at the University of Minnesota St. Anthony Falls Laboratory Outdoor StreamLab. Observations were analyzed in the context of numerical techniques ranging from simple empirical equations to a coupled hydro-morphodynamic model. To create the dataset, the water surface and the bed were imaged simultaneously using optical remote sensing techniques to create a synoptic, time-dependent map of the water surface velocities and the bed elevations around the meander bend. Bedforms reversed their plan form orientation from concave upstream to concave downstream around the meander bend as a result of cross-stream variation in the downstream sediment flux. Mean bedform wavelength was 0.73 m and mean crest height was 0.07 m but varied with distance around the meander bend. Simple equations for bedform characteristics and sediment transport rates successfully reproduced observations above of the bend apex, while the coupled hydro-morphodynamic model was required at and below the bend apex.