Influence of climate on progressive hillslope failure in Redwood Creek Valley, northwestern California

Both creep and earthflow processes control hillslope erosion over large parts of the Redwood Creek basin. The type of process and displacement rates are largely dependent on underlying bedrock type and precipitation input. Progressive creep with rates ranging from 1.0 to 2.5 mm/a dominates on slopes west of the Grogen fault underlain by sheared and foliated schists. Movement appears to respond primarily to annual increments of precipitation. Complex earthflows occur predominantly on slopes east of the Grogen fault underlain by sheared graywacke and mudstone. Movement rates range from 3.0 to 131.0 mm/a and characteristically display dominant rainy season movement.