Abstract

Understanding sediment transport and bank erosion in rivers has been a key area of active research for many decades. This research project uses a unique new Outdoor Experimental River Facility (OERF) located at the Université de Sherbrooke to run novel experiments to further our fundamental understanding of fluvial bank retreat processes. The experimental river is unique in that its floodplain is considerably larger (50 m by 20 m) than standard laboratory facilities and allows for the channel to freely migrate laterally instead of being constrained by laboratory walls. Three stages of progressively larger upstream disturbances consisting of sandbag perturbations were added to a straight gravel-bed channel to determine if any morphological changes occurred. Using an Acoustic Doppler Velocimeter (ADV), water velocity was measured to quantify the flow field and calculate bank and bed shear stress for four experimental phases: 1) no disturbance, 2) small, 3) medium and 4) large sandbag perturbations. Drone photogrammetry was used to generate digital elevation models (DEMs) to visualize erosion and deposition. Bank shear stress measurements were variable, and more research is needed to determine the optimal sampling techniques. Overall, no meander formation occurred during the experiment, which can be attributed to variables such as river armouring, lack of sediment input, and the time frame of the experiment. This study helps provide an increased understanding of bank erosion which will be useful for future bank stabilization projects related to meandering rivers in Quebec, and globally around the world.