Bedform migration in rivers

Bedform migration rate is important for estimating sediment transport in rivers. Migration rate is difficult to estimate because current theoretical approaches have limited practical use and empirical relations between migration rate and various flow parameters are not well defined. I examine field and flume data that contain information on migration rate and other flow and sediment parameters. I demonstrate an empirical relation between bedform migration rate and transport stage defined by the Shields number. I also report an investigation of the mechanisms of bedform migration in a laboratory experiment in which bed and water-surface topography data were collected under controlled conditions at different transport stages. The experiment shows migration is dominated by translation under bedload-dominated conditions, but bedform shape deformation increases with transport stage, which leads to greater variability in migration rate and bedform geometry. In addition, migration rate is conditioned by suspended-sediment transport mechanisms