ABSTRACT
In 1999 UN/IDNDR Geneva organised a mission to Lake Sarez in the Pamir Mountains of Tajikistan. This lake is up to 450 m deep, 60 km long and comprises a volume of about 17 km3. It was formed behind a huge natural dam which came into existence in 1911 when – triggered by an earthquake – a giant landslide of about 2 km3 of rock and debris blocked the Murgab River Valley. The geotechnical hazard assessment from a one-week visit of the dam site and the lower part of the lake resulted in several conclusions and recommendations. The danger of a general dam failure caused by the water pressure or from seepage was found to be low. The hazard however of an overtopping of displacement waves from new landslide masses falling or gliding into the lake is threatening. Especially the visible indications of instability at the right-bank slope about 4 km upstream of the dam gives rise a considerable concern. For a conclusive evaluation of the dam and the slope stabilities detailed geotechnical studies using modern methods and equipment are necessary.
