Quantifying rainfall controls on catchment-scale landslide erosion in Taiwan

Abstract

Landslide erosion is a dominant hillslope process and the main source of stream sediment in tropical, tectonically active mountain belts. In this study, we quantified landslide erosion triggered by 24 rainfall events from 2001 to 2009 in three mountainous watersheds in Taiwan and investigated relationships between landslide erosion and rainfall variables. The results show positive power-law relations between landslide erosion and rainfall intensity and cumulative rainfall, with scaling exponents ranging from 2·94 to 5·03. Additionally, landslide erosion caused by Typhoon Morakot is of comparable magnitude to landslide erosion caused by the Chi-Chi Earthquake (MW = 7·6) or 22–24 years of basin-averaged erosion. Comparison of the three watersheds indicates that deeper landslides that mobilize soil and bedrock are triggered by long-duration rainfall, whereas shallow landslides are triggered by short-duration rainfall. These results suggest that rainfall intensity and watershed characteristics are important controls on rainfall-triggered landslide erosion and that severe typhoons, like high-magnitude earthquakes, can generate high rates of landslide erosion in Taiwan. Copyright © 2012 John Wiley & Sons, Ltd.