Landslides affecting sedimentary characteristics of reservoir basin

Abstract

Typhoons Aere (2004) and Matsa (2005) caused high nephelometric turbidity in the Shihmen reservoir in northern Taiwan, jeopardizing the operation of the reservoir for several days, and ultimately impacting the living conditions and economy of the downstream residents. The torrential rains caused landslides and debris flows in upland areas, and flowed into riverbeds, likely contributing significantly to the suspended sediment yields in the reservoir. This investigation elucidates how upland landslides affect sediment attributes in the reservoir basin. Study methods including field observations, spatial analysis in GIS and aerial photo interpretation are adopted to trace the sediment sources and contributing factors to the landslide. Torrential rains induced landslides and debris-flows upland, causing river incisions and soil erosion in landslide areas lacking vegetation. These factors, together with the conditions of the engineered structures and geologic vulnerabilities of the area, caused suspended sediment yield in the reservoir. The high nephelometric turbidity could potentially reoccur, with masses of landslide-derived sediment remaining upland and in the riverbed

Use of a total station to monitor post-failure sediment yields in landslide sites of the Shihmen reservoir watershed, Taiwan

“…Among these landslides, 97.54% of them were below medium-scale according to Cornforth's (2005) classification, with most occurring along rivers and roads. Due to the significant increase in unvegetated areas at these landslide sites, the quantity of increased suspended sediment was approximately 2.79 × 10 7 m 3 following Typhoon Aere (Chen et al, 2010). In this situation, the role of post-failure sediment yield needs to be identified for the purpose of reservoir sedimentation management.…”

An object-based approach for semi-automated landslide change detection and attribution of changes to landslide classes in northern Taiwan

“…Most of the observed slope failures in the Baichi catchment are shallow landslides that occur on slopes with a soil depth less than 2 m ). Typhoon Aere brought more than 1600 mm and Typhoon Matsa over 1200 mm of accumulated rainfall to the Shihmen Reservoir watershed, whereby Baichi and Yufeng were the heaviest affected catchments (Chen et al 2010).…”

Modeling Typhoon‐Induced Alterations on River Sediment Transport and Turbidity Based on Dynamic Landslide Inventories: Gaoping River Basin, Taiwan

“…Typhoon Aere and the associated landslides caused a historically high turbidity event in the Shihmen Reservoir in August 2004 resulting in a 17-day water service stoppage in Taoyuang County [24]. Thereafter, a continuous turbidity meter became an essential instrument for decision making with regard to drinking water treatment during typhoon events.…”