The cross-sectional shape of a bedrock channel reflects the channel's history of incision. Although bedrock erosion due to impacts from saltating bed load particles is an important mechanism shaping bedrock channels, models of channel shape have thus far neglected the effects of sediment. Here, we present a model in which the cross-sectional shape of a bedrock channel evolves in response to abrasion from saltating bed load particles. We calculate the distribution of velocity and boundary shear stress with a two-dimensional hydrodynamic model, and we assume bed load is transported at capacity at the lowest point of the channel. Localized areas of alluviation emerge depending upon channel geometry and the imposed sediment supply, and bedrock erosion occurs in nonalluviated areas where there is bed load transport. The model captures the so-called “tools” and “cover” effects, and it simulates the dynamics between sediment supply and channel shape previously observed in experiments.