In the Manning equation the hydraulic radius can be defined as the cross-section dimension of the shape. In pipe flow the bed shear stress is assumed to be uniformly distributed along the wetted perimeter which cannot be true in open channel flow. Hence, three approximation of the true boundary shear-stress distribution are examined and more practical conveyance depth or resistance radius formu...

An experimental study with four different types of bed conditions was carried out to understand the effect of roughness in open channel flow at two different Reynolds numbers. The bed conditions include a smooth surface and three different roughness conditions, which were generated using sand grains with a median diameter of 2.46 mm. The three rough conditions include a surface with distributed...

[1] Field studies suggest that bedrock incision by granular flows may be the primary process cutting valleys in steep, unglaciated landscapes. An expression has been proposed for debris flow incision into bedrock which posits that erosion rate depends on stresses due to granular interactions at the snout of debris flows. Here, we explore this idea by conducting laboratory experiments to test th...

[1] Abrasion by bed load is a ubiquitous and sometimes dominant erosional mechanism for fluvial incision into bedrock. Here we develop a model for bedrock abrasion by saltating bed load wherein the wear rate depends linearly on the flux of impact kinetic energy normal to the bed and on the fraction of the bed that is not armored by transient deposits of alluvium. We assume that the extent of al...

We show that a freshly sedimented bed composed of spherical grains settles and creeps forward over extended periods under an applied hydrodynamic shear stress τ∗, which is below the critical value τ∗ c for bedload transport. The rearrangements are found to last at least over millions of times the sedimentation time scale of a grain in the fluid. Compaction occurs throughout the bed, but creep i...