Characterization of landslide distribution and sediment yield in the TsengWen River Watershed, Taiwan

Abstract Sediment yield is one of the primary variables of the global denudation system and is often adopted as a measure of terrestrial erosion rates in watersheds. In general watersheds, sediment supply and transport are two of the major mechanisms that may alternate sediment yield. The ordinary approach to conduct sediment prediction is to assume that erosion rates and average annual sediment yields are affected by mean annual precipitation. However, this assumption cannot fully reflect the behavior of sediment yield in regions with relatively high temporal variability. In this study, the TsengWen River Watershed (TWRW) was investigated to characterize the landslide distribution and the associated sediment yield. The results show that lithology can influence the frequency-area distribution of landslides and hence can control the volumetric sediment on hillslopes that contributes to fluvial systems. Short-term sediment yield in downstream reaches of channels correlated with the rainfall erosivity and the water discharge during rainstorms. The amount of supplied sediment and storm runoff on hillslopes as well as the transport capacity of river channels could create limitations in watershed systems. The large amount of sediment transported by rivers is attributed to the additional supply of sediment materials from upland sources such as hillslopes. Subsequent storm events could change the relationships of the sediment supply with respect to water discharge. Hence, large rainfall events are crucial for controlling sediment production, storm runoff on hillslopes, and the transport capacity of river channels in medium watersheds. In addition, anthropogenic forces may also create corresponding impact on the relationships of sediment yield, supply, and transport processes.