Estimation of sediment volume of debris flow caused by extreme rainfall in Taiwan

Taiwan has experienced frequent extreme weather events in recent decades. There is a clear trend of a decreasing number of rainy days but with much higher concentration of rainfall. The debris flows caused by torrential rains have caused severe damages to infrastructures (roadways, bridges, lifelines, and buildings) and loss of life in many recent typhoon events in Taiwan. To gauge the risk of a debris flow, it is often necessary to estimate the sediment volume of the debris flow, which is the focus of this paper. A large database involving 59 rivers and streams in Taiwan is developed based on the rainfall data between 2001 and 2009. Each data point in the database includes the sediment volume of a debris flow and its attributes including physiographical parameters, geological index, and rainfall factors. Based on multiple linear regression analysis, an empirical model is developed for estimating the sediment volume of debris flow considering watershed area, landslide area, geological index, cumulative rainfall, and rainfall duration. Characteristics and limitations of this model are examined and comparison with other models is made.