"7" Debris Flow of National Highway in Bulunkou Township, Akto County, Xinjiang

On July 27th, 2065438 18: 30, Kizilsu Kirgiz Autonomous Prefecture in Xinjiang (hereinafter referred to as Zhou Ke) is located at Bulunkou Township National Road in Akto County 16 16km (75 06' 51"east longitude and 365438 north latitude).

Due to the early warning and prediction of geological disasters before the disaster, the relevant departments made corresponding emergency arrangements. Due to timely and accurate monitoring and early warning and rapid emergency rescue, at least 10 people may be killed or injured and many vehicles may be damaged.

2 General situation of geological disasters

2. 1 Geological environment conditions

(1) terrain. Debris flow disaster is located in the southern mountainous area of Akto County, with strong river cutting, developed gullies, serious weathering and erosion of bedrock, rich loose deposits, vegetation only developed on both sides of the valley, and little vegetation on the mountain surface. Generally, the slope of mountain is above 35, and the longitudinal slope of valley is above15. The bedrock of the mountain is exposed, and the valleys are covered with gravel, medium fine sand and silty fine sand. The landform type of this section is typical valley landform (Figure 1).

(2) Formation lithology. The Cenozoic strata in Akto County are the most developed, followed by Paleozoic strata, and the pre-Paleozoic strata are occasionally exposed. Debris flow areas are mainly developed in Silurian-Devonian (S-D), Devonian (D) and Carboniferous (C), with complex lithology, mainly composed of sandstone, schist, phyllite, mica schist, marble limestone, sandstone, mudstone, conglomerate, shale and mudstone.

(3) Meteorology and hydrology. The disaster occurred in the eastern Pamirs, which belongs to the extremely cold climate. There are no obvious four seasons, only cold and warm seasons. Above 3000m above sea level, it is cold and snowy, and the annual temperature is below 0℃. The snow area in mountainous area is 790km2, and the glacier area is 600km2. Snow covers all year round, glaciers melt to form many rivers and lakes, and many springs overflow, so surface water is abundant. Gezi River system, where debris flow disaster is located, is the largest river system in Akto County. Originating from the southwest slope of Gong Geer-Mouche Tage Glacier and the north slope of Sarekuole Ridge, it has many tributaries, large flow and long flow direction, with a drainage area of 9560km2 and annual runoff of 985 million m3.

Figure 1g 3 14 Schematic Diagram of Debris Flow in Akto County

2.2 Geological hazard characteristics

Along the 3 14 national highway in Akto county, there are many types of debris flow geological disaster zones caused by snowmelt flood. Due to the influence of high temperature, the debris flow disaster formed snowmelt flood and triggered debris flow, with an accumulation volume of nearly 2000m3, blocking the road of National Highway 3 14.

Debris flow disaster occurred in the north bank of Gezi River. The mouth of the debris flow gully is 3 1.59m above sea level, the length of the main gully is about 5.3km, and the confluence area of 354 gullies is about 6.2km2, which finally flows into Gezi River. Debris flow gully consists of two gullies (Figure 2), roughly divided into two sections, and the length from the gully mouth of 3250m to the gully mouth of 5300m is about 4km2. It is characterized by a V-shaped valley with a large cutting depth. The channel is characterized by a lower width, a narrower middle width and a wider upper width. The minimum width of the ditch bottom is 10m, and the maximum width is above 100m, which is the debris flow formation area and circulation area. The terrain on both sides of the valley is steep, the slope angle on the left bank is about 55, and the bedrock is exposed in a large area; The slopes on both sides of Zhongshan are relatively gentle, with a slope of about 45, and the vegetation development is less; The slope angle of the left bank is about 50, and the bedrock upstream of the two gullies is exposed and covered with snow. From below 3200 meters above sea level to Gezi River, it is relatively flat, and a large number of early floods or mudslides accumulate breccia, gravel and gravel. All accumulated along the way. In the debris flow area, some stone dams are built along the main rivers in two valleys on both sides of the highway, and the length of the stone dams is about 240m m m.

2.3 Cause analysis

The gully and mountain where the debris flow disaster occurred is high and deep, with steep terrain and natural slope greater than 45. The longitudinal slope of the gully bed is steep, the bedrock on the slope is exposed, the vegetation is undeveloped, and the shape of the watershed is convenient for water collection. The alluvial fan where the national highway G3 14 is located is relatively flat, which is beneficial to the accumulation of debris flow deposits. The geological structure in valley and mountain areas is complex, faults and folds are developed, neotectonic activity is strong and earthquake intensity is high. The bedrock of the mountain is mainly slate and phyllite, with developed joints and fissures, broken rock mass, loose rock structure and severe weathering and crushing, which provides a rich source of debris for debris flow.

Characteristics of Debris Flow Disaster at 3 14 National Road 16 16 km in Akto County.

High temperature snow melting provided hydrodynamic conditions for the occurrence of this debris flow disaster. Under the stable control of the Iranian subtropical high, a high temperature weather process with the longest duration and strongest intensity occurred in this area on July 26th. The highest temperature in Akto County broke through the historical extreme, reaching 39 ~ 4 1. Due to this high temperature weather, the height of the zero-degree layer rose to about 5900m, while the height of the snow line in this area was 4300m·m m. Due to the continuous high temperature, the alpine snow in this area melted rapidly.

To sum up, under the combined action of unfavorable factors such as topography, stratum lithology, geological structure and meteorology and hydrology, this debris flow disaster was born.

3. Geological hazard inspection and monitoring

3. 1 Daily inspection and monitoring

The mountain section of National Highway 3 14 is the key section of geological disaster prevention and control. In the report of geological disaster investigation and zoning in Akto County in 2002, this section was listed as a geological disaster-prone section (Figure 3). Geological disasters along the way are mainly monitored by highway departments, border checkpoints and land departments, and warning signs of geological disasters are erected along the way (Figure 1).

The inspection and monitoring of geological disasters in this area shall be carried out at multiple levels and departments. From March to April every year, Xinjiang Land and Resources Department and Xinjiang Geological Environment Monitoring Institute (Geological Disaster Emergency Center) carry out inspections in flood season, and timely check the development of geological disaster prevention and control in flood season before flood season. Zhou Ke Municipal Bureau of Land and Resources and County Bureau of Land and Resources strengthened the inspection of geological disasters in flood season according to the inspection situation. County Land and Resources Bureau issues disaster prevention cards to surrounding farmers and herdsmen, and border inspection stations publicize and educate passing vehicles to remind them of precautions when entering mountainous areas. Road administration, land and border inspection departments set up eye-catching warning signs along the road to remind passing vehicles and personnel. On this basis, we will further implement the responsibility for disaster prevention. The land border post where the disaster monitoring point is located has arranged a special person to be responsible for monitoring, keep the information flowing, and do a good job in duty recording and dynamic monitoring. To ensure the safety of life and property of passing vehicles and personnel and local farmers and herdsmen.

3.2 Emergency early warning mechanism

On the morning of July 26th, Zhou Ke Meteorological Bureau predicted, "From July 27th to August 4th, there will be the longest and strongest high temperature weather process in Zhou Ke since this summer; The highest temperature in Atushi and Akto County will reach 39 ~ 4 1℃, and the highest temperature in Akto County will exceed the historical extreme. Due to this hot weather, the zero floor height in Zhou Ke will rise to about 5,900 meters.

On the afternoon of July 26th 16: 30, experts from Akto Meteorological Bureau, Land and Resources Bureau, Civil Affairs Bureau, Traffic Police Brigade, Transportation Bureau, Water Conservancy Bureau (Flood Control Office), Water Pipe Station, Animal Husbandry and Veterinary Bureau, Bulunkou Township and other departments held a multi-department joint consultation meeting on meteorological disaster prevention, releasing the early warning and forecast information of "The strongest high temperature weather this summer is coming, beware of snowmelt floods".

After the meeting on the afternoon of July 26th, Akto County Bureau of Land and Resources immediately notified the heads of governments of townships (fields), heads of mining enterprises and cadres of the Institute of Land and Resources by telephone, text messages, etc., and asked the townships (fields) and mining enterprises to make all preparations for preventing and avoiding geological disasters. Strengthen the monitoring and inspection of mass prevention and treatment, and report any abnormal situation at any time. In particular, after receiving the notice, Bulunkou Township Government, Oyitake Traffic Police Squadron and Gaizi Border Inspection Station immediately stepped up monitoring to remind farmers, herdsmen and passing vehicles to pay attention to preventing floods and mudslides.

On July 27th 19: 08+07, the Gaizi frontier inspection station of the frontier detachment of Zhou Ke, Xinjiang, the Armed Police received help from the masses, claiming that a large-scale mudslide occurred in the section of China-Pakistan Friendship Highway1614 ~1616 km. Since then, the local township government, border police, road administration departments and traffic police departments have dealt with it in time to ease traffic. Fortunately, the debris flow occurred at night, and the traffic volume was not large, causing no casualties or property losses. At 2 am on July 28, the blocked road section has resumed traffic.

Fig. 3 Debris flow area is the key prevention and control area for geological disaster investigation and zoning.

4. Safe haven resettlement for geological disasters

Before the disaster, the Akto County Bureau of Land and Resources promptly notified the heads of township (field) governments, mining enterprises and cadres of the Institute of Land and Resources to prepare for the prevention and avoidance of geological disasters; Strengthen the inspection and monitoring of group monitoring and prevention, and remind the threatened objects to pay attention to prevent floods and mudslides. After the disaster, the traffic police of the traffic police squadron of Oyitake, the cadres of land and resources, and the cadres of Bulunkou township government rushed to the scene at the first time to rescue the trapped people, mobilize vehicles, clean up sediment, clear roads, and guide the trapped vehicles, so that the trapped vehicles and the trapped people could pass through the disaster site in time and safely.

5 Experience and Enlightenment

Judging from the case of successfully avoiding the geological disaster of debris flow at 3 14 National Road 16 16km in Bulunkou Township, Akto County, Zhou Ke, it is the key to timely forecast and arrange the implementation of disaster prevention.

(1) Pay attention to early warning and forecast of special weather. The key to this successful hedging is that the land and meteorological departments regularly carry out long-term meteorological forecasting and early warning of geological disasters in flood season. The meteorological and land departments of Zhou Ke and Akto counties predicted the occurrence of geological disasters in advance according to the weather conditions, and held special meetings and chambers of commerce, attaching great importance to meteorological early warning and forecasting of geological disasters.

(2) The key to disaster prevention and avoidance is implementation. After the consultation, the work organization of each unit was in place, the early warning information was released in time, and the disaster prevention measures were seriously implemented. Akto County Bureau of Land and Resources informed all units in time, grass-roots land offices, frontier inspection stations and other departments actively cooperated, and traffic police, road administration and other departments took effective measures to divert traffic in time, which finally ensured the success of this hedging and avoided the loss of life and property of passing vehicles and personnel to the greatest extent. The successful avoidance of this mudslide disaster not only improved the emergency response ability of local relevant departments to sudden geological disasters, but also enhanced the emergency response ability, safety awareness and self-protection awareness of passing vehicles and farmers and herdsmen to sudden geological disasters. It can be seen that as long as effective measures are taken, properly handled and early prediction and prevention are made, it is entirely possible to successfully avoid the loss of people's lives and property caused by geological disasters.