Linzhi immigrant relocation

At about 20: 00 pm on April 9, 2000, a landslide occurred in Zhamunonggou, Zangbu River, Gong Yi, bomi county, Linzhi District, lasting about 10 minute, with a sliding range of about 8 kilometers and a height difference of about 3,330 meters. The landslide cut off the Zangbo River in Gong Yi (the riverbed elevation is 2190m, and the Zangbo River in Gong Yi is the second tributary of the Yarlung Zangbo River and the first tributary of the Palong Zangbo River), forming a accumulation body with a length of about 2,500m, a width of about 2,500m, an average height of about 60m and a volume of about 300m3, which has become a "natural dam". According to experts' calculations, the vertical drop of sliding objects is 3,000 meters, the maximum horizontal moving distance is about 8,500 meters, and the average moving speed reaches 48 meters per second. Such ultra-high-speed movement, long-distance migration and huge accumulation volume are the first in China and rare in the world. The whole landslide accumulation process only takes 6 minutes! In this short period of time, nature has completed the construction amount equivalent to 1 1 Three Gorges Dam.

The main reason for the landslide is that the temperature is warming and the ice and snow melt, which makes the large bedrock wedge located at Xuefeng Mountain, 5520 meters above Zhamunonggou, collapse. Hundreds of millions of landslides are in a saturated and unstable state, sliding down the steep slope below at high speed, hitting the old accumulation body below, shoveling down the mountains on both sides, transforming into "clastic stones" and falling into the river at high speed. The biggest landslide in China in the past century is also rare in the world.

Due to the huge amount of sediment, the water level of Gong Yi Lake has risen rapidly, and it is now in the melting period of ice and snow and rainy season, and the increase of the lake is increasing day by day. Within 62 days, the water level of the lake rose by an average of 0.95 m per day, with the maximum daily increase of 2.37 m, the cumulative water level increased by 55.36 m, the maximum water depth increased from 7.2 m to 62. 1 m, and the lake area expanded from 9.8 square kilometers to 52.7 square kilometers, which was 5.4 times that before the landslide blocked the river, resulting in a large area of the lake area being flooded.

On April 18, following the instructions of Vice Premier the State Council and the State Flood Control and Drought Relief Headquarters, an expert working group on flood control and drought relief, composed of the State Flood Control and Drought Relief Headquarters (hereinafter referred to as the State Flood Control Headquarters) 1 1, came to Linzhi and arrived in the disaster area of Gong Yi to guide the disposal of the catastrophic landslide and debris flow disaster in Gong Yi. Through field investigation, the expert group predicted that due to the continuous rise of Gongyi Lake and the flood season of Zangbu River in Gong Yi in early June, the amount of water entering the lake will increase sharply. In the middle and late June, the amount of water in Gong Yi Lake may increase to about 4 billion cubic meters, and the water level will overflow the dam crest. Because the landslide is mainly composed of sandy soil with stone or block stone overhead structure, the soil is loose, with low water content, uniform particle size and poor water erosion resistance. Once the lake overflows the top of the dam, such a large head and storage capacity will cause the danger of dam break, so if the overflow prevention measures are not taken, the consequences will be very serious. According to the actual situation on site, the expert group studied and formulated engineering measures to cut dams, open canals and reduce elevation, and tried to reduce the great harm that high water level may cause to the upstream and downstream, with non-engineering measures such as resettlement as the main content to reduce disasters and eliminate risks.

To this end, Tibet has begun the largest assembly of construction troops in history. In just 33 days, a diversion canal with a depth of 24 meters, a length of 850 meters and a width of 150 meters was dug, creating a miracle in the history of engineering in Tibet and even in the history of water conservancy in China. However, compared with the extremely huge landslide accumulation, this is only a superficial scratch on its surface, and dam failure is inevitable.

The earth-shattering potential and powerful destructive power of dam-break flood may be difficult to describe in words. Within a few hours, the flood caused the water level in the downstream river to skyrocket by 40 to 50 meters, and the maximum flow of the river reached 654.38+0.24 million cubic meters per second, which was 28 times of the annual average flow of the Yarlung Zangbo River (4,425 cubic meters per second)!

Drainage began on June 7. Unexpectedly, the turbulent water made the diversion channel wider and wider, and the dam burst at 7 pm on June 10. The monstrous flood roared down the Gong Yi Tibetan cloth. At 9: 30 that night, Tongmai Old Bridge was destroyed, and Tongmai Water reached 50 meters (30 meters higher than the old bridge deck) at about 3 am on June1/KLOC-0. The flood leveled all the artificial facilities in the whole section of Chilong Zangbo, and the destructive power crossed the Yarlung Zangbo River to Medog. Naturally, the Sichuan-Tibet highway section from Tongmai to Pailong was completely destroyed.

The disaster stopped Gong Yi from storing cloth for more than two months, and accumulated more than 3 billion cubic meters of water. Gong Yi tea gardens and lakeside villages were flooded, and more than 4,000 people were relocated. After the emergency trench digging by the Armed Police and the People's Liberation Army, the diversion canal penetrated the dam surface on June 5 and burst on June 8, with a flood peak of 60 meters high and lasting for 6 hours. By June 1 1 day, the whole lake was completed. As a result, all bridges in Zangbo, Palong Zangbo and Yarlung Zangbo River Grand Canyon areas in Gong Yi were washed away, and roads along the river, including the 3 18 Yantou Tongmai Bridge on Sichuan-Tibet Highway, were washed away, and roads along the river, including the 3 18 Bomi-Linzhi section made in China, were interrupted and paralyzed. At the same time, the disaster interrupted the traffic in Medog Menba and Loba, and nearly 10,000 people in more than 90 townships in Medog, Bomi and Linzhi counties became isolated islands after the disaster.

The flood has left many scars on both banks of the downstream river: bridges, roads and communication facilities built successively along the Zangbo, Palong Zangbo and Yarlung Zangbo rivers in Gong Yi for more than 40 years have all been destroyed, the cross-sectional shape of the river has changed from "V" to "U", and the river has been widened by more than 2 times, reaching 10 times. The previously relatively stable valley slope was strongly eroded and transformed, which led to the instability of a large area of mountains.

The high-speed landslide, river blocking, inundation, dam break, flood and other chain disasters caused by this catastrophic landslide have left a shocking landscape of disaster relics for people to watch, experience and study, which has become one of the main landscapes of Gong Yi National Geopark: from Tongmai to Gong Yi, along the way, it can be seen that the dam break flood formed a scouring zone about 50 meters high on both sides of the riverbed, the original forest and topsoil were stripped off, and the exposed rocks were like gray corridors; Below the dam breach, you can see the deep ditch and large-scale stone beach washed out by the original river bed, which is a scene of drought and flood. After the dam break, the natural dam across the banks of Zangbo in Gong Yi has been cut off by half, but the original cone-shaped mound and bunker are still clearly visible on the surface of the preserved accumulation body. On the bank of Zangbo, Gong Yi, near Zhamunonggoukou, the large-scale forest lodging zone and residual pile zone caused by debris flow and shock wave are still vivid; At the mouth of Zhamunonggou, we can see that most of the peaks have been cut off after the landslide in the ditch, forming a terrible scene of a landslide with a height difference of 1020 meters. ...

The lower reaches of the Yarlung Zangbo River in India are seriously affected. According to Agence France-Presse, seven states along the Yarlung Zangbo River suffered from severe floods. 94 people died, 2.5 million people were homeless, and some roads and railways were paralyzed.