In this study, we are primarily concerned with shallow landslides that involve poorly consolidated soils or
colluviums on steep hill slopes. Shallow landslides, sometimes referred to as debris flows, mudslides,
mudflows, or debris avalanches, are rapidly moving flows of mixes of rocks and mud, which have the
potential to kill people and destroy homes, roads, bridges, and other property. This study addresses those
landslides caused primarily by prolonged, heavy rainfall on saturated hill slopes characterized by high
permeability. Rainfall-triggered landslides may mobilize into fast-moving mudflows, which generally
present a greater hazard to human life than slow-moving, deep-seated slides. Although most parts of the
world have experienced major socioeconomic losses related to landslide activity (Sidle and Ochiai, 2006),
currently no system exists at either a regional or a global scale to identify rainfall conditions that may
trigger landslides.