The impacts on the rates of landsliding by forest management activities (road construction and timber harvesting) in northwestern California are evaluated. The effects of these land disturbing activities were studied for various geomorphic zones of a watershed, valley inner gorges, land with slopes greater than 80 percent, and “other” watershed lands. Analysis of historical aerial photography and computer generated digital terrain slope maps was used to determine changes over time in the distribution of active landslides in third order watersheds, where the present watershed conditions vary from pristine to highly disturbed. In all of the disturbed watersheds, forest management activities increased the landslide rates (landslides per square mile) of each geomorphic zone. The valley inner gorges and land with slopes greater than 80 percent had the greatest landslide rate increases. Managed valley inner gorges and managed slopes greater than 80 percent had 11 to 26 and 3 to 26 times more landslides per square mile than managed “other lands,” respectively. These data suggest that the valley inner gorges and land with slopes greater than 80 percent are the most landslide prone geomorphic zones in a watershed and the most sensitive to forest management activities.