Drought year changes in streambank profiles on incised streams in the Sierra Nevada Mountains

After streams incise, they evolve through channel widening and adjustment of bank angle and bank shape. The rate of bank erosion and the influence; of vegetation on the processes of adjustment on bank morphology are not well understood. To evaluate the role of vegetation in streambank changes, this study included monthly measurements of bank movement along incised streams during a drought. Data were collected throughout one year along four streams in the Sierra Nevada Mountains. Streambank shape varied among five classes: vertical, boomerang, “L”, short-cliff, and constant slope. Each shape included similar profile segments: top-bank, cliff, mid-slope, and toe-slope. The bank shapes did not follow location-for-time substitution models and erosion was not related to stream velocity. Relationships among profile shape, profile segment, and vegetation apparently influenced bank erosion, deposition, and net change. Most deposition occurred on vegetated, moderately steep slopes. Conversely, most erosion occurred on steep, bare banks. Rhizomatous plants retarded erosion, whereas forbs often grew in depositional areas.