Analysis of bedload transport in laminar flows Nian-Sheng Cheng School of Civil and Environmental Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, cnscheng@ntuedu.sg Abstract Bedload transport generally depends on the bed shear stress and Reynolds number. However, knowledge of the Reynolds number effect on the transport rate is relatively limited because many sediment transport problems are often studied only for the condition of turbulent flows. As an extreme case to reflect the viscous effect on sediment transport, sediment transport in laminar flows is considered in this paper. A stochastic approach is adopted to explore how the transport rate can be associated with characteristics of laminar flows. First, the probability of erosion in the absence of turbulence is assumed to depend only on the randomness of bed particles. The probability is then applied to formulate the sediment transport rate, of which the derivation is made largely based on the Einstein's bedload theory. The theoretical result indicates that the dimensionless transport rate for laminar flows is dependent on the dimensionless shear stress and dimensionless particle diameter or the shear Reynolds number. Comparisons are finally made between the derived formula and an empirical correlation available in the literature.