A stochastic description of sediment motion and rest regimes under low bedload transport

Michele Guala, SAFL Associate Director of Research, Associate Professor of Civil, Environmental, and Geo- Engineering, University of Minnesota

The kinematics of sediment particles is investigated by non-intrusive imaging to provide a stochastic description of bedload transport in conditions near the threshold of motion. In particular, we focus on the cyclic transition between motion and rest regimes to quantify the statistical properties of the particles waiting times, inferred to be responsible for anomalous diffusion, and so far elusive. Despite obvious limitations in the spatio-temporal domain of the observations, we are able to identify the probability distributions of the particle step time and step length, streamwise and spanwise velocity, acceleration, waiting time, and thus distinguish which quantities exhibit well converged mean values, based on the thickness of their respective tails. The experimental results shown here, under five different transport conditions, describe grain scale kinematics and dynamics at increasing shear stress and represent a benchmark dataset for the stochastic modeling of bedload transport.