I would like an investigation report on "Landslide and Debris Flow Disasters". Here are the materials. School geography competition questions, free play, <1500 words

Tengchong County is located in the western part of the southern section of the Hengduan Mountains and belongs to the source area of ​​the upper reaches of the Irrawaddy River in the Indian Ocean water system. From July 17th to 19th, 2004, the Houqiao, Zhonghe and Mingguang, Gudong, and Jietou counties in the upper reaches of the Binlang River, a tributary of the Daying River, and Mingguang, Gudong, and Jietou in the upper reaches of the Longchuan River were hit by heavy rains. It rained only on July 17th and 18th. 159.6mm, large-scale landslides and debris flow disasters occurred around July 19, causing serious casualties and huge property losses, which attracted great attention from the Party Central Committee, the State Council, Yunnan party and government leaders, and all sectors of society [1]. During the July 19 disaster, 21 towns in Tengchong County were affected to varying degrees, including 42 village committees and 316 villager groups in 7 towns in the central and northern parts of the country: Houqiao, Mingguang, Diantan, Gudong, Jietou, Qushi and Zhonghe. The disaster was relatively serious (Figure 1), causing direct economic losses of 1.36×108 yuan [1]. In this disaster, 7 people died, 2 were missing, and 4 were injured in the county. 420 people were injured or injured due to the disaster. The disaster-affected population was 1.76×105. 3,426 victims and people in dangerous areas needed emergency relocation; 5,138 houses collapsed and damaged. During the period, 3.00×105kg of stored grain was lost, and 2530 livestock died; 4373hm2 of crops were affected, 2755hm2 were damaged, 1232hm2 failed to harvest, and 387hm2 of fields were washed away and buried; trees and seedlings were seriously damaged, and more than 10 forestry processing enterprises were affected and suspended production; 92 County, township, and rural roads were affected by the disaster, with 150 kilometers of roads destroyed, 130 bridges and culverts, and all roads leading to the China-Myanmar Houqiao Port interrupted; traffic in tourist attractions such as Huoshan, Atami, Heshun, and Beihai was interrupted; 18 embankments were damaged, and 8 embankments were breached. 147 bank protections were damaged, 50 drinking water projects for humans and animals were damaged, 154 large and small ditches with a length of 125km were damaged, 5 small hydropower stations were damaged, causing the shutdown of Longjiang Level 2 and Level 3 power stations; 100km of communication lines, 20km of transmission lines, and 18 Primary and secondary schools were affected by the disaster, and school buildings and walls collapsed severely. Fortunately, the students were in summer vacation, otherwise the consequences would be disastrous.

1 Types and causes of disasters 1.1 Types and distribution of disasters. Through field surveys and surveys, it is believed that Tengchong The 7.19 disasters are mainly landslides and debris flow disasters, which are accompanied by slope collapse and collapse in the early stage of their formation, and high sand content flash floods and flood disasters in the later stage. Among them, landslides and debris flows are mainly concentrated in 7 villages including Yongxing Village, Qingkou Village, Dongcun and Shangjie Village in Houqiao Town on the upper reaches of the Binang River in the north-central part of Tengchong County (5 people died due to the disaster), Xinqi and Gaotian in Zhonghe Township , Dacun (1 person died) and Mingguang Township (1 person died), Diantan Town (2 missing) and Gudong Town in the main stream of Longchuan River and its tributary Mingguang River Basin; scattered in mountainous areas such as Jietou Township and Qushi Township , and flash floods and floods with high sand content are mainly distributed in the Pingba area along the Binlang River and Mingguang River (Figure 1). 1.2 Disaster development background In terms of administrative division, Tengchong County is affiliated to Baoshan City, Yunnan Province, and is located at the junction of Baoshan City, Nujiang Lisu Autonomous Prefecture, and Dehong Dai and Jingpo Autonomous Prefecture, and is adjacent to Myanmar in the northwest. The county covers an area of ​​5845km2 and has a population of 6.10×105 people, including Han, Hui, Dai, Wa, Jingpo, Lisu, Deang, Achang and other ethnic groups [2]. The county is located on the western slope of Gaoligong Mountain, and its terrain is an alternating pattern of alpine canyons, intermountain fault basins, and plateau planations. The terrain is higher in the north and lower in the south; the highest point in the county is Danaozi Peak of Gaoligong Mountain in the northeast corner, with an altitude of 3780.9m; the lowest point is located on the Suqing River at the junction of Tengchong, Longling and Lianghe counties in the south, with an altitude of 930m and a relative height difference of 2850.9m. Tengchong is the last stop on the Southwest Silk Road. It is famous for its volcanic geothermal landscape and very active seismic activity. The main rivers flowing through the county are the Daying River and its tributary Binlang River, and the upper reaches of the Ruili River, the Longchuan River. , the flow direction is generally north-south, and both belong to the Irrawaddy River system. The county has a north subtropical plateau monsoon oceanic climate, with distinct dry and wet seasons, mild climate, droughts in winter and spring, and floods in summer and autumn. The county seat is located in Tengyue Town on the flattened surface of the Yunnan-Guizhou Plateau, with an altitude of 1,600m, an average annual temperature of 14.9°C, and an average annual precipitation of 1,478.5mm. Precipitation in the rainy season accounts for 85% of the annual precipitation. The zoning of rainfall is obvious, with single-point heavy rains. More[3]. 1.3 The main causes of disasters. The Tengchong 7.19 landslide and debris flow disasters all occurred in the central and northern areas with extremely high forest vegetation coverage. Among them, short-duration, high-intensity heavy rainstorms are the main external triggering factors of the disaster. Strong fault activity, neotectonic movement and strong winds The loose layer of granite is an intrinsic factor in its formation. The huge height difference, high steep slopes and large slopes in the mountain canyon area provide superior potential energy conditions for its formation. In addition, the heavy early rainfall in June and July made the The long-term immersion and water saturation of rock and soil bodies will eventually lead to landslides and collapses in the mountains, resulting in landslides and debris flow disasters. Some unreasonable human development and construction activities, such as mining ores, building hydropower stations, indiscriminate logging, and deforestation for farming, etc. This intensifies the hazards and losses of disasters. 1.3.1 Heavy rainfall factors are affected by the combination of the westward-extending Pacific subtropical high pressure and the Indian Ocean monsoon low pressure. From July 17th to 19th, heavy rainfall occurred in the Nujiang area of ​​​​western Yunnan, Baoshan City, and Lushui, Fugong, and Dehong Prefecture. Tengchong and Yingjiang and other places experienced a large-scale heavy rainfall process, with the highest rainfall intensity in Tengchong and Yingjiang.

According to rainfall observation data from the Tengchong County Meteorological Bureau[1], the precipitation from January to July 2004 was 126.1mm more than the same period in previous years. By July 19, the county had experienced moderate to heavy rain or above 11 times. Since the 7th, continuous rainy weather has occurred throughout the county. During the period, the total precipitation was 195.1mm, and the daily rainfall reached more than 20mm for 5 days, of which the precipitation on the 11th and 19th were 28.0mm and 39.5mm respectively; and from the 17th to 20th At 08:00 on the 20th, the rainfall in the county reached 81mm. The precipitation center in the northern part of the county received a maximum rainfall of 159.6mm from July 17th to 18th. According to the memories of local elderly people aged 70 to 80, a heavy rain that occurred once every 100 years occurred in 1903, but such a heavy rain has never occurred since 1946. Therefore, the heavy rain on July 17-18 can be regarded as a heavy rain in terms of rainfall frequency. 60a encounter. According to the observation data of the Tenglongqiao Hydrological Station in Tengchong County, the peak flow of the Longchuan River flood caused by the heavy rain was the largest since the station was established, reaching 1660m3/s, which is a huge flood that has not been encountered in 50 years. The heavy rain had obvious vertical zoning, that is, the heavy rain mainly occurred in the middle and high mountainous areas above 2000m above sea level. The annual rainfall in Houqiao reached more than 3000mm, and landslides and debris flow disasters also mostly occurred in the middle and high mountainous areas above 2000m above sea level. The Houqiao, Diantan, and Mingguang areas in Tengchong County and Zina and Zhanxi in Yingjiang County were the center of the heavy rain, and the disaster was the most severe, which fully reflects the consistency of the distribution of landslides, debris flows, and rainfall. Tengchong County has a high natural vegetation coverage, which was 59% in 1950. Due to the large-scale felling of natural forests, it decreased to 38% in 1990, resulting in serious water and soil erosion. However, in the central and northern regions, the vegetation coverage is much higher than that in other parts of the county. Although the vegetation is well protected, it still causes serious landslides and debris flow disasters. Therefore, extremely heavy rain is the fundamental cause of the disaster. According to the investigation, at 9:30 on July 18, a landslide occurred in Jiagu Mountain, Zhongtang Village, Mingguang Township, killing one person; at 0:00, July 19, a mudslide occurred in Yongxing Village, Houqiao Town, killing one person; at 1:30 a.m. , four surveyors of the Binlang River IV Power Station encountered a mudslide in Jiejie Village, Houqiao Town, and all died; on the afternoon of July 19, a landslide occurred in Bajiao Ridge, Yongxing Village, Houqiao Town, killing a primary school teacher. The flash floods and floods caused by the heavy rain also caused the collapse of bridges and flooding, which also killed three people. It can be seen that disasters occurred concentratedly from the night of July 18th to the early morning of July 19th, with the majority occurring on the 19th, so this disaster was named the 7.19 Tengchong landslide and debris flow disaster. 1.3.2 Topographic factors (1) Height difference. Tengchong County mostly belongs to Zhongshan and high mountain areas, with Zhongshan as the main area. In the central and northern areas where this disaster was severe, the highest altitude is the highest point in the county. Da Naozi Peak, located in the northeast corner of Gaoligong Mountain, has an altitude of 3780.9m. Generally, the mountain range has an altitude of 2000-3000m, and the valleys and valleys have an altitude of 1000-1500m. The height difference between the ridges and valleys is 1000-1500m, and the maximum height difference is 2780.9m. The potential energy conditions are very good. superior. At the same time, the above-mentioned areas are located on the western slope of Da'aozi Mountain and the southern slope of Daniang Mountain (3323.3m). Blocked by high mountains, the warm and humid airflow from the south rises along the windward slope, forming a major rainfall concentration zone in the mid-to-high mountainous area, which is the basis for disasters. Occurrence provides motivation[3]. (2) The slope of the hillside and the decrease of the ditch bed. The study area is a typical mid-alpine deep canyon area, but compared with other typical landslide and debris flow areas in my country, the slope of the slopes in the area is relatively gentle. According to preliminary statistics, except for a few hills with a slope >40°, the slopes of most hillsides range from 30° to 35°. The slopes of the slopes of Yongxing Village and Gaotian where landslides occurred are around 35°. The river bed ratio drops in the upper reaches of the Binlang River and the Mingguang River are both above 10%, while the gully bed ratio drops in places such as Houqiao, Mingguang, Gudong, Gaota and Atami where gully debris flow occurs are above 20%, and the slope of the slope debris flow is Around 30°. It has the basic terrain conditions for the development and movement of landslides and debris flows. (3) Water system structure. The disaster mainly occurred in the upper reaches of the Binlang River, a tributary of the Daying River, and the main tributaries of the Longchuan River in Tengchong County. The two rivers have well-developed water systems with numerous branch ditches, which are distributed on both sides of the river in the form of veins. The valleys and river valleys are all in a typical V shape. Blocked by fan-shaped accumulations of debris flow on both sides and some gorges, some river sections form intermountain basins and valleys. U-shaped valley. Due to the development of collapses, landslides and debris flows, the riverbed is lined with boulders and boulders, ups and downs, and siltation is very serious [4]. 1.3.3 Geology and structure The Tengchong area is located to the west of the Lushui-Ruili fault, adjacent to the junction of the Indian and Eurasian plates, and belongs to the southern part of the Bossula Ridge-Gaoligong Mountains fold belt of the Gangdese-Nyenchen Tanggula fold system. It is famous for its developed fault structures, young active volcanoes, strong geothermal activity and seismic activity [3]. Most of the area is occupied by migmatized rocks and granites. The remaining Upper Paleozoic epimetamorphic rocks are scattered among the acidic intrusions. The Upper Tertiary and Quaternary systems of the Cenozoic are along the Longchuan River, Daying River and Areca Distributed along the river, medium-basic volcanic rocks cover most areas. Affected by fault activity, seismic activity, and geothermal activity, the strata in the area are very fragmented and loose, and are highly susceptible to weathering, which provides a sufficient material basis for the development of landslides and debris flows. The survey results show that the thinnest weathered layer is 10m and the thickest is more than 100m. Most of the landslides and debris flows caused by the 7.19 disaster, such as the debris flow in Yongxing Village, Houqiao Town, the debris flow in Shangjie Village, the Bajiaoling landslide, and the Gaotian Village landslide in Zhonghe Township, etc. All develop along the weathering layer.

The neotectonic movement in the study area is very strong, which is manifested in strong and frequent seismic activity, widespread exposure of hot springs, uplift of mountains, and subsidence of basins, which provide sufficient material foundation and energy conditions for the development of landslides and debris flows [4]. 2. Characteristics of landslide and debris flow disasters 2.1 Sudden outbreak and rapid disaster caused the Tengchong 7.19 landslide and debris flow flash flood disaster. The heavy rain occurred suddenly from July 17 to 19. The rainstorm was intense and lasted for a long time. The rain was concentrated in the northern mountainous area. In addition, the heavy rain occurred late at night. , there was heavy early rainfall, the mountains were high and the slopes were steep, the slopes were long and the ditches were short, so the disaster occurred quickly and was difficult to prevent and avoid. 2.2 A disaster chain is formed, and the disaster extends from mountainous areas to intermountain plains. This disaster was triggered by heavy rainstorms. The disaster process is: first, collapses, landslides and slope debris flows are formed in the upper reaches of the valley and on the slopes; landslides and collapses cause runoff on the slopes. Under erosion, part of it is directly converted into slope debris flow, and part of it is accumulated with slope debris flow in the slope foot and ditch, forming a ravine debris flow due to flash flood erosion; after the debris flows out of the ditch, it joins the mainstream flood to form a flood with high sand content, and carries it with it. Large amounts of driftwood and rocks were moved downstream of the river. Therefore, the disaster formed a disaster chain from heavy rain - landslide - debris flow - flash flood - driftwood flow - flood with high sand content. The disaster extended from the mountains to the foot of the slope, and gradually extended from the mountainous area to the flat dam area, and also from the mountain village. Expand to villages and towns. 2.3 The scope of hazards is concentrated and regional. Because this heavy rainstorm is relatively concentrated and highly localized, disasters and hazards only occur in 7 towns in the northwest of Tengchong County and 3 adjacent towns in Yingjiang. Seven villages including Xingcun, Qingkou Village, Dongcun and Shangjie Village, Zhonghe Township Gaotian, Dacun and Mingguang Township, Diantan Town and Gudong Town were the hardest hit, while the losses caused to other towns in the east and south were relatively relatively lighter. 2.4 The number of disasters is large, the scale is small, individual destructive power is strong, and casualties and property losses are heavy. Field investigations found that heavy rains caused more than thousands of landslides and debris flows in the northern region of Tengchong, posing threats and causing harm to more than 100 people.

Most of them are small in scale, with landslide volumes and debris flow deposits ranging from tens to hundreds of cubic meters, and most of them are located outside residential areas and farmland, so they do not cause serious disasters. However, the landslides and debris flows that caused the disaster were relatively large in scale, with most of them measuring 1,000m3. The Takata landslide had a volume of 2.00×105m3. Due to its large scale, it was extremely destructive after sliding, posing a serious threat to roads and villages. 2.5 The frequency of outbreaks is low. According to local elders, between July and August 1946, severe rainstorms, landslides and debris flows occurred in Houqiao and the adjacent China area. Many villages were relocated from the mountains after that disaster; In 1952, a large-scale landslide occurred near Xiaoshuijing in Houqiao Township, killing 7 people. The disasters around 1975 and then in 1984 were more serious, but the scale and disaster losses were far less than the 7.19 disaster in 2004; the 58a disaster from 1946 to the present I have never seen such a heavy rainstorm. It can be seen that the outbreak frequency of the 7.19 debris flow disaster can be regarded as once every 60 years. The outbreak frequency is extremely low and is rare in history. 3. Prediction of the development trend of landslide and debris flow disasters. Before 2001, a total of 302 geological disaster points including landslides, debris flows, unstable slopes, collapses and mine goafs were discovered in the county [3]. After 1999, precipitation was obviously too high. Afterwards, landslides and debris flow activities were intense in Atami and other places, and geological disasters became more active, posing serious threats to local villages, towns, tourist facilities, and rural towns. Continuous heavy rains since July 2004 have triggered thousands of landslides and debris flows in Tengchong, causing disasters and hazards at more than 100 disaster points, 25 of which seriously threatened the lives and property of more than 1,000 households and more than 5,000 people. , causing serious harm to towns, counties, farmland, irrigation canals, highways, etc. This disaster was controlled by the center of heavy rain, and all occurred in the central and northern regions where the disaster was relatively mild before. However, the middle and lower reaches of the Longchuan River in the south, where the geological disaster was originally more serious, did not suffer serious disasters this time. This shows that when the geological conditions, terrain conditions, solid material conditions, etc. are all in place, heavy rain has become the most important triggering factor for landslides and debris flow disasters. After the 7.19 disaster, in addition to the severe losses caused by the geological disasters directly caused by the above-mentioned 7 towns, it also caused a large number of potential landslides and collapses, destroyed the forest vegetation, fragmented the slopes, caused a large number of slope instability, and formed many airspaces. and tensile cracks, many large-scale old landslides have been resurrected one after another. The area where the disaster occurred is also a local heavy rain center. Heavy rains are very frequent. Once a heavy rainstorm occurs, it will induce a series of geological disasters and form a disaster chain. Investigation shows that the occurrence of the 7.19 disaster kicked off a new round of geological disaster activities in Tengchong County. In addition to the area where this disaster occurred, new disaster dangers have also been induced in other areas. For example, a large number of landslides are in the creeping stage, and some are already in a critical state before sliding. Debris flows have abundant loose solid material reserves. Therefore, in the future, triggered by external factors such as disastrous heavy rains or earthquakes, landslide and debris flow disasters will gradually become more active, and the harm to human life and property and the mountain environment will be further intensified, and the losses caused by disasters will also be further expanded. Disaster prevention The situation of disaster relief and disaster reduction is very serious.

4. Current emergency disaster reduction measures 4.1 Strictly investigate potential disaster hazards and promptly relocate people and property from serious hazard areas. At present, in addition to strengthening disaster relief, resettlement and dynamic monitoring of existing disasters and existing disaster hazard points, the masses and the geological community should be extensively mobilized. Disaster monitoring and alarm personnel and professionals conduct inspections of hidden danger points of geological disasters in various townships, villages, etc., to identify the distribution status of disasters, the scope and extent of hazards, and development trends, and to grasp the overall situation of disasters. For serious hidden danger points where prevention and control projects cannot be implemented temporarily, people and property should be transferred in a timely manner to reduce losses caused by disasters [5]. 4.2 Formulate contingency plans for sudden disasters. The occurrence of the 7.19 disaster has sounded the alarm for the government and competent authorities at all levels. In response to the severe geological disaster situation, a disaster emergency leading group should be established to formulate emergency plans for sudden geological disasters, including escape routes for people before the disaster, resettlement sites, disaster relief and rescue, fund raising, personnel evacuation, transportation guarantee, etc. Make careful and sound plans for material transportation, resettlement of disaster victims, health and epidemic prevention, communication transmission, etc. Once a disaster occurs, the emergency plan should be implemented in accordance with the formulated emergency plan to ensure that it is foolproof and orderly. 4.3 Promptly publicize and popularize the basic knowledge of geological disasters to the masses. At present, it is necessary to publicize and popularize the basic knowledge of geological disasters, especially how to identify the signs of geological disasters and how to escape, avoid disasters, rescue and choose temporary residence and settlement after a disaster. The broad masses. We should work together and pool our wisdom to give full play to and mobilize the people's initiative in disaster prevention and relief, minimize casualties and property losses, and fully implement the "people-oriented" disaster reduction purpose. 4.4 Strengthen monitoring, early warning and forecasting of disaster points. Before the 7.19 disaster, the Tengchong County Land and Resources Department and the Meteorological Department cooperated to make disaster forecasts. Based on the monitoring forecasts, many people in disaster risk areas were evacuated in a timely manner, thus avoiding greater disasters. Loss, monitoring, forecasting and alarm work play a very important role in disaster reduction and prevention. Therefore, we should continue to strengthen the monitoring of landslide and debris flow disaster points with high potential threats and endanger people's lives and property during the flood season, and predict and forecast based on weather forecasts and various signs of disaster activities. 4.5 Do a good job in emergency disaster assessment in the resettlement areas for the victims. After the 7.19 disaster, the reconstruction and resettlement of the disaster areas are the most urgent issues facing the cadres and the masses in the disaster areas. For locations where disaster victims are to be resettled, geological disaster surveys and emergency risk assessments should be carried out, and construction in disaster-prone areas should be avoided as much as possible. During the investigation, it was found that some villagers had built new houses on unsafe high and steep slopes. Therefore, land and rural cadres should strengthen the supervision of newly built housing for disaster victims, and strictly prohibit arbitrary digging and filling when building construction side roads, restoring destroyed roads, water canals, reclaiming farmland, etc. 4.6 Construct emergency disaster reduction projects to improve disaster prevention and resilience. For landslides that are currently in the creeping stage and critical state, cracks should be filled in time, and water from the surrounding and slope surfaces should be directed out of the landslide body to prevent water from seeping into the slope body; For paddy fields on landslides, the amount of irrigation should be reduced to prevent water seepage; excessively steep slopes, dangerous rocks, and dangerous trees should be appropriately cut and cleared [4]. For mudslides and flash floods that endanger villages and towns, temporary drainage projects such as lead wire gabion diversion embankments and dry-wall retaining walls should be constructed to prevent overflow and flooding of mudslides and floods. At the same time, clear the narrow valley sections of rivers and ditches, culverts, bridges, silt and buildings that impede flood flow, and dredge rivers and ditches. 5 Disaster Prevention and Mitigation Measures 5.1 Carry out detailed investigation and activity assessment of mountain disasters. After the 7.19 disaster, thousands of new disaster points were added in Tengchong County, and the number, distribution area and activity status of disasters changed. Therefore, a new round of detailed investigation of geological disasters should be carried out as soon as possible to find out the activity patterns, hazard levels and future development trends of disasters, so as to provide a basis for future disaster zoning, risk assessment, monitoring and prevention. 5.2 Risk analysis and zoning of mountain disasters Risk zoning is a regional prediction of disasters, which can provide guidance for local urban and rural construction, highways, water conservancy, farmland planning, and disaster prevention and control [6]. On the basis of detailed investigation of regional geological disasters, we will classify and partition future development based on the influencing factors of the disaster (distribution density, height difference, slope, lithology, structure, earthquake, heavy rain, forest vegetation, etc.) and the severity of the danger zone. Resettlement of disaster victims, relocation of residents in dangerous areas, and disaster prevention and mitigation are extremely important. 5.3 Systematically carry out mountain disaster management work. For disaster points that seriously threaten towns, factories, mines, important water conservancy and power facilities, and larger residential areas, planning suggestions, feasibility studies, and project establishment work for disaster prevention and control projects should be carried out as soon as possible, and the work should be carried out in phases and in batches according to the Prioritize and implement project management. In addition, strengthening the restoration and protection of forest vegetation in disaster areas and improving soil and water conservation also play a very important role in reducing the occurrence and severity of landslides, debris flows and flash floods [6]. 5.4 Establishing a mountain disaster forecasting and early warning system. Since geological disaster points are widespread and are mostly located in remote mountainous areas, the current meteorological, hydrological and disaster monitoring stations cannot meet the needs of forecasting and forecasting. Therefore, a geological disaster monitoring and forecasting system should be established as soon as possible, such as using remote rain gauges and meteorological radars to monitor rainfall in real time, and using GPS to monitor landslide displacement and deformation. 5.5 Strengthen departmental collaboration and build a disaster prevention platform. The monitoring, forecasting and prevention of landslide, debris flow and flash flood disasters is a complex system project, involving not only the land and resources department, but also administrative management, water conservation, water conservancy, hydrology, meteorology, earthquakes and Disaster relief and many other departments.

Therefore, the competent leaders should coordinate various departments to jointly build a mountain disaster prevention platform to achieve maximum resource sharing, information exchange, and improve the overall mountain disaster defense capabilities.