Glacial catastrophe of 20 September 2002 in North Osetia

The Dammed Saniba Lake

[62] This lake began to form after the formation of an ice avalanche (Figure 4) in the Karmadon Trough on 20 September 2002. The ice mass blocked the exit from the right lateral canyon damming the channels of two small rivers: the Kauridon R. with the flow rate of 1.2 m³ sec^-1 and the Fardon R. with the flow of 0.8 m³ sec^-1. This produced a basin of a future lake, which began to be filled with water. The total debit of these two rivers was about 2.0 m³ sec^-1, capable of the water accumulation of 170,000 m³ day^-1.

[63] However, the situation developed much more rapidly. On 24 September 2002, trying to find an exit, the water of the Genaldon R. broke through the right side and flowed to the lake during four days. By the beginning of this break, the lake contained about 0.6 million m ³ of water. On 28 September this break through terminated, yet, the water of the lake rose to the height of 20 m more, its volume being 2.5 million m³. Two small streets were flooded in the Gornaya Saniba Village. On 18 October, 2002, the lake water level ceased to grow, but on October 22 a water channel was formed at the surface of the ice along the right side of the valley. By that time the area of the lake was 260,000 m², and its volume was 3.5 million m³. No one knew how all of this will end.

[64] The inhabitants of the flat land settlements, located along the banks of the Gizeldon R., (the Genaldon R. being its right tributary, see Figure 3), felt a great danger and were ready to abandon their houses in the case of the lake breaking through. Observations of the lake state were carried out during the days and nights. The channel in the ice surface grew notably deeper. The water level in the lake began to decline very rapidly and became 7 m lower during 15 days. The second break of water took place in mid-July 2003, when the water level became 2.5 m lower during 2 days.

[65] On 10 and 11 July the lake was inspected by the experts of the Moscow University, and the first topographic survey was carried out. In 10 July, 2003, the lake contained 1.32 million m³ of water. The lake water table was at the level of 1319.63 m.

Figure 23

Figure 24

[66] The third break-through occurred at the beginning of December. During ten days the level of the lake water descended by 2.8 m. By 1 January, 2003, its water level was 1314.45 m. In 2004 the water level of the lake continued to decline at a rate of 1 cm a day. In 25 August its level was 1312.77 m, and in 25 November, 1311.9 m. About 0.5 million m³ of water remained in the lake (Figure 23). In August 2005 the lake looked fairly stable (Figure 24).