Author(s): W. W. Bell; T. Donich; K. L. Groves; D. Sytsma
Linked Author(s):
Keywords: Warning; GLOF; Moraine failure; Nepal
Abstract: Tsho Rolpa, the largest glacial lake in Nepal is located in the Rolwaling Valley, approximately 30 km Southwest of Mt. Everest. It has formed over the last forty years as the Trakarding glacier has stagnated, melted and retreated. The lake, which is at an elevation of 4580 m, is approximately 3 km long, 0. 5 km wide and up to 130 m deep. It is retained by a natural moraine dam that is unstable and threatens to burst. If the dam is breached, the resulting flood of approximately 80 million cubic metres of water would cause serious damage for 100 km or more downstream, threatening as many as 6000 lives, the construction site for a 60 MW hydroelectric project and other infrastructure. The damage would have a serious impact on the economy of Nepal. The current risk of a failure is considered to be high and increasing rapidly. This paper describes the design, and installation of a warning system downstream of Tsho Rolpa. The warning system is based on Extended Line of Sight VHF radio technology and will relay any alarm from sensors located immediately downstream of Tsho Rolpa to the seventeen warning stations along the Rolwaling and Tama Koshi Valleys. Warning is issued by air horns backed up by electronic sirens. The system is fully redundant so that failure of two successive stations would have to occur in order to prevent the warning signal from being received by the most downstream station. The sensing system is also fully redundant and multiple sensor failures would have to occur before a false alarm or missed event could occur. Several of the GLOF warning stations, as well as a GLOF sensing station, will also transmit and receive signals from a Meteor Burst master station installed in Western Nepal, thus providing further redundancy to the system in the event two or more successive stations should fail. The system was designed, supplied and installed in an accelerated program in order to have it operational by late May for the 1998 monsoon season. It has operated continuously since then through a severe monsoon season.
Year: 1999