Morphological and Sediment Supply Controls on Lateral Bedrock Channel Erosion

In bedrock rivers, bedload transport causes abrasion not only vertically but also laterally. Bank erosion causes sinuosity changes and lateral migration that influence terrace formation, hillslope base level and drainage divide evolution. We conducted laboratory experiments and developed equations to predict lateral bedrock abrasion rates, which are poorly understood compared to vertical incision rates. We systematically varied channel curvature, lateral (cross-stream) bed slope, and the supply rate of bedload. Surprisingly, bank abrasion decreases with increasing channel curvature due to secondary circulation. Bank erosion increases with lateral bed slope because it increases sidewall sediment concentration. However, at higher sediment supply rates lateral erosion is ≈constant due to particle interactions and dynamic cover effects. We propose equations which capture the sensitivity of bank erosion rate to the experimental variables. Our model will be useful for predicting future lateral erosion and for constraining bedload transport rates from bedrock channel morphology.