Landslide Hazards along River Corridors - Rock fall potential

Rock fall is a type of landslide that occurs in bedrock where single or multiple rocks are dislodged and fall from steep cliff faces. In a typical alpine setting, cliffs are located on the upper slopes of a mountain with a talus below, extending to the base of the mountain. The talus is composed of rocks that have fallen from the cliff face and accumulate below the cliff. The talus marks the limit of most rock fall from the cliff, but a few boulders that fall from the cliff travel beyond the toe of the talus. It is these outliers that can pose a hazard to adjacent development (see figure "b" below). Rock fall can be triggered by earthquakes, freeze-thaw cycles, or severe weather. Tumbling boulders falling from a cliff face are fast moving and can level virtually anything in their path.