Landslide trends under extreme climate events

Does the incidence of landslides increase with rainfall? To what extent will landslides occur as a result of previous extreme-rainfall events? This becomes important to know under expected climate changes. This research studies the relationship between landslide density and rainfall depth in landslide susceptibility zones on the Zengwen River basin in southwestern Taiwan. The relationship is then applied to predict landslide occurrence during a near future rainfall event and a predicted extreme rainfall at the end of this century, as estimated from statistical and dynamic precipitation downscaling. The results indicate increased incidence of landslides with rainfall between a lower rainfall threshold and an upper range of values. Near the upper range of values, the rate of increase in the incidence of landslides slows, tending to become saturated at a certain landslide density. This finding is different from models proposed in previous studies which show a quadratic increase with large rainfalls. The different rates of increase for landslides with large amounts of rainfall will result in various hazards that may require special attention.