Landslide dams in Central Asia region (特集近年の地すべりダム)

概要

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The Central Asia region has been a scene of numerous large-scale bedrock landslides that have blocked river valleys producing landslide-dammed lakes, more than 100 of which still store water. The largest one is the Usoi dam 2.2 km3 in volume and more than 550 m high in Pamirs (Tajikistan) that originated in 1911 due to strong (M7.2) earthquake. It forms the 500 m deep Sarez Lake - the world deepest natural reservoir that poses a threat to Central Asian countries located downstream in the Pianj - Amu Daria River basin. Though many of landslide-dammed lakes should be considered as stable and safe features, catastrophic outburst floods that occurred in 20th Century, emphasize high potential hazard of such natural blockages. Several prehistoric landslide-dammed lakes in Pamirs and Tien Shan with intact dams were filled by lacustrine sediments, but most of natural dams were breached and deeply eroded providing excellent opportunity to study their internal structure and grain-size composition - parameters determining dams short-term and long-term stability at a large extent. Additional factors, increasing or decreasing rockslide dams stability are exemplified by case studies from the Central Asia region.
2010-11-25