A physics-based feature-scale erosion model is critical to forming a cohesive understanding of chemical-mechanical polishing because it can link chemical effects modeled on the particle scale to process conditions modeled at the wafer scale. Such a model is described here for polishing processes utilizing a hydrodynamic slurry layer. The stresses induced by the flowing slurry on feature surfaces are computed and used in erosion models that incorporate fracture mechanics and chemistry empirically. Good agreement with experimental erosion profile data is demonstrated and the effect of hydrodynamic layer thickness and feature pattern density on planarization rate is investigated.