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Moraine dam hole of roughly 50 m wide and 40 m high

5. Detailed geology

The sudden outburst and flood of rocks is clearly confirmed by the large, 800 m long and 300 m wide boulder field in front of the moraine dam.
Intermittent floods formed either due to choking of the glacial dam hole, also see detail, of around 2000 square meters by the glacial ice or continued collapse of the dam. Gravel deposits of 10 to 30 cm thick and up to 10 meters wide between the boulders confirm this.
Down-streams the around 200 to 300 m wide river bed shows evidence of up to 10 to 12 m high water floods in the outer bends from sand deposits and bushes affected by the water flood.
Rocks in the river beds are up to 2 meters large and probably carried along for several hundreds of meters but bigger rocks up to 8 meters across have also been moved over a short distance as reported by the villagers. One big rock 6-8 meters across near Tangnag was used by porters to sleep under the overhang and is still lying in the river bed near its original place.

6. Glacial lakes bursts in Nepal and Tibet

6.1 Overview before 1998

A good overview of glacial lake floods is given by ISSUES MOUNTAIN IN DEVELOPMENT 1997/3
Here 9 major glacial lake outburst floods are reported that took place between 1935 and 1985. The best documented flood is the one of 1985 near Namche Bazar.
Other examples of glacial lake bursts (to be completed):
North of Ringmo (near Junbesi), a little lake broke out some 15 years ago. Reported by Sherpa mountain guides living in the area. No casualties.
Lake in the Dhaulagiri (More info needed).
Tshu Bung Lake in Rolwaling in 1991.
( more info needed; to be completed )

6.2 Other glacial lake bursts in 1998

Sherpa guides reported that in 1998 in Tibet near Gaudari (?) a natural glacial lake dam broke and that it flooded the Sun Kosi river between Kathmandu and Charikot, east of Kathmandu, running along the main highway to from Kathmandu to Tibet.