The Sediment Production and Transportation in a Mountainous Reservoir Watershed, Southern Taiwan

This study examined differences in landslide sediment production and sediment transportation abilities of reservoir watersheds in different geological environments after extreme rainfall. The watershed in this study covered an area of 109 km²; the upstream river banks of the reservoir contained interbedded shale and faulted shale and had a sandstone dip slope. This paper uses a LiDAR-derived DTM taken in 2005 and 2010 to investigate the landslide sediment production and riverbed erosion and deposition in the watershed. This study also applied the conservation of mass concept to analyze the sediment outflux in the subwatersheds. The research results indicated that although the right bank, which had interbedded shale and a sandstone dip slope, had a substantially greater number of landslides, the sediment production of it was less than that of the left bank, which had numerous deep-seated landslides caused by fault zones. However, affected by the higher sediment production of the left bank and under the same stream power, the left bank subwatersheds also had higher sediment outflux.