Flow Strength and Bedload Sediment Travel Distance in Gravel Bed Rivers Journal Articles uri icon

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abstract

  • AbstractThe quantification of bedload sediment transport in rivers is possible from statistics of individual particle displacements. However, there is a lack of empirical basis for a universal relation between particle displacement distance and hydraulic drivers. Previous work suggests that a simple linear relation exists between the energy of a flood and the mean travel distance of bedload particles. Such a relation would be advantageous, but a consistent model able to collapse the data from different rivers has not been developed. Here, we develop a predictive relation from a unique data set collected in three watersheds from a single region but contrasting hydrologic regimes due to urbanization and storm water management. Additional data from two rivers from outside the region are used to validate the model. We show that the mean of an exponential distribution of surface particle travel displacements can be reliably predicted from either the cumulative discharge or stream power exceeding the mobilization threshold, which is calibrated using field data. The strength of the relation decreases after large flood events that appear to cause tracer burial due to vertical mixing. This result indicates that the relation is most applicable for the entrainment phase of transport in which tracers are dispersing over the bed surface. Tracer movements become more challenging to predict over a long series of events due to burial and eventual tracer slowdown, but the relation remains valid for the particles located on the bed surface, making it suitable for analyzing the impact of climate and landscape changes over time.

publication date

  • July 2022