Technical Studies

In 2009, Typhoon Marokot on its way passing through Taiwan brought large amount of rain to the watershed of upstream of Tsengwen Reservoir. The cumulated rainfall amount was estimated to have a return period of 200 years. The rainfall had induced numerous landslides and caused tremendous amount of surface soil erosion. To estimate future sediment transport capability of the Reservoir, this study applied a mechanistic-based model to investigate the cause-effect relationships between rain-induced landslide, geologic and hydrologic factors in the watershed. Furthermore, by conducting soil sample testings and installing slope movement monitoring stations, the study utilized rainfall infiltration and slope stability analyses to assess landslide potential of various slopes in the watershed upstream of the reservoir and estimate sediment yield to the Reservoir under different rainfall scenarios. Through the analysis framework developed in this study, including landslide risk assessment model, river sediment migration model, and reservoir sediment transport model, one is able to estimate the amount of sediment coming into the reservoir from its source. The framework also allows the evaluatoin of the effectness of water-soil conservation work in the watershed on the reduction of sediment yield due to the implementation of project “ Regulation of Zengwen, Nanhua, and Wushantou Reservoirs and Stabilization of Water Supply in Southern Taiwan”.