Erosional landform map of the Redwood Creek drainage basin, Humboldt County, California, 1947-74

Landslides and actively eroding stream channels disrupt roads, damage valuable timberland, and increase stream sediment loads in northwestern California. This 1:62,500 photointerpretative map shows the distribution of ten common types of fluvial and mass-movement erosional landforms in the drainage basin of Redwood Creek in 1947 and 1974. The mapped landforms include slides, slumps, large compound earthflows, debris avalanches, unstable streambanks and adjacent hillslopes, small mass-movement features, questionable or inactive landslides, deeply incised amphitheater shaped drainage basins, small actively eroding water courses, and actively eroding main channel stream banks. The map legend describes these landforms and the techniques used in preparing the map. The amount and diversity of erosional activity increased greatly between 1947 and 1974. This increased activity apparently reflects major floods in 1953, 1955, 1964, and 1972, as well as the start of large scale, tractor-yarded clearcut timber harvest in the basin. (Woodard-USGS)