A landslide is defined as the rapid downslope movement of slope-forming materials—rock, soil, debris, or combinations of these materials. In regions of the world where steep slopes combine with heavy-moisture episodes, mass movement and landslides are a risk. Landslides are difficult to predict and prepare for because a wide variety of factors influence the likelihood of a landslide occurring. Landslides are an important geomorphic process in mountainous regions, fundamentally shaping the hydrology, geology, and ecology of a place. This natural phenomenon presents a significant challenge to people who place property and community in the path of potential landslides, challenging planners, government personnel, and citizens to better understand the complexities of landslide occurrence in their region in order to protect infrastructure, resources, property, and people.