"6·" Extremely large flash flood and debris flow in Gongshan County, Nujiang Lisu Autonomous Prefecture, Sichuan
1 Overview of debris flow
From 5:10 to 6:30 pm on June 23, 2011, there was a sudden heavy rain in Pengdang Township and Bingzhongluo Township in the northern part of Gongshan County, accompanied by Strong convective weather such as thunderstorms and strong winds caused single-point heavy rainfall, causing flash floods, debris flow disasters and wind disasters to varying degrees throughout the county. Bibili River and Shuangla River in Bingzhongluo Township, and Longpo River and Geza River in Pendang Township broke out to varying degrees. flash floods and debris flow disasters. Mudslide disasters and wind disasters affected 11,035 people in the county, 250 households and 500 houses were damaged (168 houses of 42 households were destroyed), and direct economic losses were about 12.5 million yuan; agriculture was severely affected, with 2,396 acres of corn affected and 1,450 acres of grass and fruits affected. , more than 1,200 large and small livestock died, 125 pens collapsed or washed away, and direct economic losses were 6.45 million yuan; 300m of roadbed (surface) was washed away, 1 stone arch bridge with a clear span of 30m and a height of 9m, and 3 bridge culverts. 18,000 m3 of retaining walls, 83 landslides along the highway, and direct economic losses of 25 million yuan for transportation facilities; 5.6 km of farmland water conservancy projects such as Bibili, Longpo, and Geza were destroyed, and the Bibili river protection embankment and 14. For the 5km rural drinking water safety project for humans and animals, the direct economic loss for water conservancy facilities reached 4.8 million yuan; the direct economic loss for power grid and communication facilities reached 1.27 million yuan. Shuanglahe Power Station and industrial and mining enterprises suffered direct economic losses of 10 million yuan. The total economic loss reached 44.82 million yuan. Due to the sound early warning and forecasting group and detection group prevention systems, strong organization and timely evacuation, there were no casualties. 376 households and 1,059 people were urgently relocated, including 42 households and 147 people from the severely affected households.
This disaster was mainly caused by the extremely large flash flood and debris flow on the Bibili River that broke out at 6:30 pm on June 23. According to on-site investigation, the length of the accumulation fan at the mouth of the debris flow ditch is about 400m, the maximum width is about 130m, and the accumulation volume is about 110,000 m3. According to the investigation of the debris flow, it was determined that the debris flow was a viscous debris flow. Debris flow fluid has no structure and is a mixed accumulation of unsorted mud and gravel. The fluid is thick and has strong buoyancy. The mud residue in the basin is not obvious, and the accumulation at the ditch mouth is fan-shaped. From the investigation of the accumulation fan at the mouth of the ditch, it was found that the slurry is well mixed with rocks. The coarse particles in the non-slurry part are composed of solid materials such as rocks, gravel, trees and sand. The debris flow is estimated to have a weight of about 19kN/m3 and a flow rate of 600m3. /s.
2 Monitoring and emergency avoidance
After receiving the disaster report, the Gongshan County Land and Resources Bureau quickly launched the geological disaster emergency plan and immediately organized staff to rush to the scene as soon as possible to carefully Check the disaster situation and immediately report it to the superior land and resources department, and establish a leading group for land and resources emergency and disaster relief work, which consists of five working groups:
(1) Disaster investigation team, responsible for the geological and geological conditions of the disaster point Conduct a comprehensive investigation of hidden dangers, ensure inspections, records, and timely reporting to each level;
(2) The expert investigation team invites geological disaster emergency investigation experts from the Yunnan Provincial Department of Land and Resources to rush to the disaster area for disaster response Investigation, and responsible for technical guidance of prevention and control work, preparation of geological disaster prevention and control plans, emergency plans, disaster site surveys and rescue plans, delineation of dangerous areas, affected areas, and avoidance areas, suggestions for the establishment of monitoring points, identification of disaster causes, and Investigation and evaluation, and finally a disaster investigation report.
(3) The logistics support group is responsible for the raising and deployment of emergency tools and rescue materials such as rescue and disaster relief vehicles, and the life security of the personnel of the rescue and disaster relief working group and the provincial and departmental expert groups.
Figure 1 Debris flow accumulation area and small landslide on the opposite bank
Figure 2 Debris flow destroyed houses and silted up cultivated land
(4) Hidden hazard monitoring team, responsible for disaster response Establish monitoring points in dangerous areas upstream of the points, establish geological disaster early warning systems in conjunction with meteorological and water conservancy departments, formulate monitoring systems, implement monitoring responsibilities, and be responsible for monitoring and forecasting possible secondary disasters.
(5) The information materials team conscientiously implements disaster reporting, duty and other systems, collects and organizes relevant geological disaster information and emergency and disaster relief work in a timely manner, and promptly reports disaster situations to superior departments. Achieve uploading and distribution, and smooth flow of information.
After the disaster, the Gongshan County Party Committee and the county government quickly established an emergency and disaster relief leading group and on-site command headquarters. The People's Liberation Army, armed police officers and soldiers, and public security officers arrived at the scene immediately and joined the local people of all ethnic groups in the rescue operation. Disaster relief efforts. The disaster relief work was carried out in an orderly manner, the affected people were properly resettled, and electricity, communications, drinking water, etc. were guaranteed. The people in the disaster area have stable emotions, peaceful people, orderly lives and social stability.
Figure 3 Emergency Baotong Construction Site
3 Experience and Enlightenment
This debris flow disaster was large-scale and serious, but the early warning was timely and the masses were able to prevent and avoid disasters. They had a strong awareness of disasters, organized evacuation in an orderly manner, and did not cause any deaths. This is an emergency avoidance case worthy of summary and commendation. The success of this emergency avoidance was mainly due to:
First, attaching great importance to the investigation and prevention of geological disasters.
During the pre-flood geological disaster investigation and planning survey, the Gongshan County Bureau of Land and Resources issued a "Geological Hazard Prevention Clear Card" and a "Geological Hazard Avoidance Clear Card" to the masses, identified the person responsible for monitoring, and clarified early warning and forecasting measures. , signals, emergency escape lines.
The second is to strive to improve the early warning and forecasting and group testing and prevention systems. When the debris flow broke out, the masses discovered it and immediately called the police. After receiving the alarm, the villagers immediately ran to call. In just 5 minutes, all people within the disaster area evacuated to safety areas on both sides. When the mudslide occurred, 376 households with 1,059 people were safely relocated. Practice has proved that the group testing and group prevention system is an important magic weapon for us to overcome natural disasters.
The third is to continue to strengthen the publicity and education of geological disaster science. The Gongshan County Land and Resources Bureau has repeatedly publicized the knowledge of geological disaster forecasting and prevention to the masses, which has greatly improved the general public's awareness of disaster prevention and avoidance. This shows that only by relying on and mobilizing the masses and allowing the masses to actively participate can we effectively implement the prevention and control of geological disasters.
(The basic information for this section is provided by the Department of Land and Resources of Sichuan Province and the editor-in-chief is Zhuang Maoguo)