Sediment Entrainment Into Suspension From Granular and Cohesive Beds

Abstract In this article, we investigate the entrainment of granular sediments into suspension and, using sound theoretical arguments, derive a modified version of the Smith and McLean (1977, https://doi.org/10.1016/s0422‐9894(08)70839‐0 ) relation, where the proportionality constant is now a function of the particle Reynolds number, . The proposed relation is calibrated with data from the literature and compared with several existing models. Despite its simplicity, our results show that the new relation performs exceptionally well. Similarly, we rederive Kandiah's (1974, https://www.proquest.com/openview/1af0d87ab884c36ba8e2527de0535e59/1?cbl=18750&diss=y&pq‐origsite=gscholar ) equation for the erosion of cohesive sediment beds, demonstrating that the erosion rate parameter is proportional to the critical shear stress and depends on the bed's concentration and aggregation state. The calibrated relation, based on literature data, shows that naturally formed beds behave differently from artificially prepared ones, a difference that we attribute to distinct bed fractal structures. Our findings present compelling evidence that both granular sediment entrainment and cohesive bed erosion can be modeled similarly, with both processes being proportional to the excess shear stress exerted by the flow on the bed. Furthermore, our findings suggest that these relations can be applied under both equilibrium and nonequilibrium sediment transport conditions.