Weather forecast of street town

Tengchong County is located in the west of the southern section of Hengduan Mountains and belongs to the source of Irrawaddy River in the Indian Ocean system. In July 2004 17- 19, Monkey Bridge, Zhonghe and Mingguang, Azuma Tani and Jietou in Tengchong County, the upper reaches of the Binglang River, a tributary of Daying River, were hit by heavy rain, with rainfall of 159.6mm, with 7 in July and 18 in July alone. 7. During the 1 9 disaster, 2 1 towns in Tengchong County were affected to varying degrees, including 42 village committees and 3 16 villagers' groups in 7 towns in north-central China (Figure1), which was seriously affected. Seven people died, two were missing, four were injured, 420 were injured due to the disaster, and the affected population was 1.76× 105. It is necessary to urgently transfer and resettle 3426 victims and people in dangerous areas. The collapse damaged 5 138 houses, lost 3.00× 105kg of grain and killed 2,530 livestock. The crops were affected by 4373hm2, 2755hm2, 1232hm2, and the buried fields were washed away by 387hm2. Trees and seedlings were seriously damaged, and 10 forestry processing enterprises were affected and stopped production; 92 county, township and village highways were affected by disasters, which washed away roads 150km, bridges and culverts 130, and the whole road leading to the Monkey Bridge port in China and Myanmar was interrupted. Traffic in tourist attractions such as volcano, Rehai, Heshun and Beihai was interrupted; Damaged dike 18, burst 8, damaged revetment 147, damaged 50 drinking water projects for people and animals, damaged 54 large and small ditches 125km in length, and damaged 5 small hydropower stations, resulting in the shutdown of Longjiang II and III power stations; 100 km communication line and 20 km transmission line were damaged, 18 primary and secondary schools were affected, and school buildings and walls collapsed seriously. Fortunately, the students are all on summer vacation, otherwise the consequences will be unimaginable.

1 disaster type and cause 1. 1 disaster type and distribution Through field investigation, it is considered that the main disasters in Tengchong 7. 19 are landslides and mudslides, which are accompanied by slope collapse and collapse in the early stage, followed by high-concentration flash floods and floods in the later stage. Among them, landslides and mudslides are mainly distributed in 7 villages (5 people died due to the disaster), Qixin Village, Gaotian Village in Zhonghe Township (death 1 person), Mingguang Township (death 1 person) and Diantan Town in the upper reaches of the Binglang River in north-central Tengchong County. Tengchong County belongs to Baoshan City, Yunnan Province, located at the junction of Baoshan City, Nujiang Lisu Autonomous Prefecture and Dehong Autonomous Prefecture, bordering Myanmar in the northwest. The county covers an area of 5845km2 and has a population of 6.1×105, including Han, Hui, Dai, Wa, Jingpo, Lisu, De 'ang and Achang nationalities [2]. The county is located on the western slope of Gaoligong Mountain, and the terrain is mountainous canyons, intermountain fault basins and plateau planation planes, which are high in the north and low in the south. The highest point in the territory is Da Naozi Peak in Gaoligong Mountain, which is located in the northeast corner, and the lowest point is located on the Su Qing 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 of the ancient Silk Road in southwest China, and is famous for its volcanic geothermal landscape and active seismic activity. The main rivers flowing through the county town are Daying River and its tributaries, Binglang River on Ruili River and Chuanjiang River in Youlong, which are generally north-south and belong to Irrawaddy River system. The county belongs to the monsoon maritime climate of the northern subtropical plateau, with distinct dry and wet seasons, mild climate, drought in winter and spring, and floods in summer and autumn. The county seat is located in Tengyue Town on the planation plane of Yunnan-Guizhou Plateau, with an altitude of 65,438 0.600 meters, an annual average temperature of 65,438 0.4.9℃ and an annual average precipitation of 65,438 0.478.5 mm. The rainy season precipitation accounts for 85% of the annual precipitation, with obvious rainfall zoning and more single-point rainstorms [3]. 1.3 Disaster Tengchong 7. 19 The main causes of landslide and debris flow disasters all occur in the central and northern areas with extremely high forest vegetation coverage, among which short duration and high rainfall intensity are the main external causes of disasters, and strong fault activity, neotectonic movement and loose layer of strongly weathered granite are the internal causes. The huge height difference, steep slopes and steep valleys of alpine valleys provide superior potential energy conditions for their formation. In addition, the early heavy rainfall from June to July made the rock and soil saturated for a long time, which eventually led to landslides and collapses, resulting in landslides and mudslides. However, some unreasonable human development and construction activities, such as ore mining, hydropower construction, indiscriminate mining and deforestation, have aggravated the harm and loss of disasters. 1.3. 1 The rainstorm is affected by the western Pacific subtropical high and the Indian Ocean monsoon depression. From July 17 to July 19, heavy rainfall occurred in Lushui, Fugong, Tengchong and Yingjiang in Baoshan City and Dehong Prefecture in Nujiang area of western Yunnan. According to the rainfall observation data of Tengchong Meteorological Bureau [1], the precipitation in June 2004 was more than that in the same period of previous years1. By July 19, there was moderate to heavy rain in the county 1 1 times. Since July 7th, the total precipitation has been 195. 1mm, and the daily rainfall in five days has reached more than 20mm, of which 1 1 and 19 days are 28.0mm and 39.5mm respectively. However, from 20: 00 on 17 to 08: 00 on the 20th, the rainfall in the whole county reached 81mm. In July, * * * rainfall 17- 18, rainfall 159.6mm, according to the memory of local 70-80-year-old people, there was a rainstorm in 1903 100a, but from/kloc. Therefore, the rainstorm on July 17- 18 can be regarded as a once in 60 years in terms of rainfall frequency. According to the observation data of Tenglongqiao Hydrological Station in Tengchong County, the flood peak discharge of Longchuan River formed by this rainstorm is the largest since the station was established, reaching 1.660 m3/s, which is a once-in-50-year flood. Heavy rain has obvious vertical zonality, that is, heavy rain mainly occurs in the middle and high mountain areas above 2000m above sea level, and the annual rainfall in Monkey Bridge is above 3000mm, while landslides and mudslides mostly occur in the middle and high mountain areas above 2000m above sea level. Houqiao, Diantan and Mingguang in Tengchong County, Zhina and Zhanxi in Yingjiang County are the centers of this rainstorm, and their disasters are also the most serious, which fully reflects the consistency between the distribution of landslides and mudslides and rainfall. Natural vegetation in Tengchong county.

The degree is relatively high, which is 59% at 1950. Due to the massive felling of natural forests, it decreased to 38% in 1990, and soil erosion became more serious. However, in the central and northern areas, the vegetation coverage rate is much higher than other areas of the county. Although the vegetation has been well protected, it still forms a serious landslide and debris flow disaster Therefore, rainstorm is the root cause of the disaster. According to the investigation, at 9: 30 on July 18, a landslide occurred in Jiagushan, Tang Zhong Village, Mingguang Township, resulting in the death of 1 person. 19 A mudslide occurred in Yongxing Village, Houqiao Town at 0: 00 on July, causing 1 death; 65438+ At 0: 30 a.m., four surveyors of Binglangjiang IV Power Station were killed in a mudslide in Shang Jie Village, Houqiao Town. 19 On the afternoon of July, a landslide occurred in Bajiaoling, Yongxing Village, Houqiao Town, and 1 Primary school teachers were killed. Flash floods and floods caused by heavy rains caused the bridge to collapse and flood, which also killed three people. It can be seen that the disaster mainly occurred in the night of July 18-the early morning of July19, and the disaster was named as 7. 19 Tengchong landslide and debris flow disaster. 1.3.2 terrain factor (1) height difference. Tengchong county belongs to Zhongshan and alpine areas, mainly Zhongshan. In the north-central region where the disaster is serious, the highest altitude is the highest point in the county. Daanzi Peak is located in the northeast corner of Gaoligong Mountain, with an altitude of 3780.9 meters. Generally, the mountain elevation is 2000 ~ 3000m, the valley elevation is 1000 ~ 1500m, and the valley height difference is 1000 ~ 1500m, with the maximum height difference of 27438. At the same time, the above areas are located on the western slope of Da Naozi Mountain and the southern slope of Daniangshan Mountain (3323.3m). Due to the blocking of high mountains, the warm and humid airflow from the south rises along the windward slope, forming the main rainfall concentration area in the middle and high mountains, which provides the excitation power for the occurrence of disasters [3]. (2) Slope and trench bed slope. The study area is a typical middle-high mountain and deep canyon area, but compared with other typical landslide and debris flow areas in China, the slope of this area is relatively gentle. According to preliminary statistics, except for a few slopes >: 40, most slopes are between 30 and 35, and the slopes of Yongxing Village and Gaotian where landslides occurred are around 35. The river bed gradient in the upper reaches of Binglang River and Mingguang River is above 10%, and the gully bed gradient in Houqiao, Mingguang, Gudong, Gaotian and Rehai where gully debris flows occur is above 20%, and the slope debris flow gradient is about 30. It has the basic topographical conditions for the development and movement of landslides and debris flows. (3) Water system structure. The disaster mainly occurred in the upper reaches of Binglang River, a tributary of Daying River and Longchuan River in Tengchong County. The water system of the two rivers is developed, and there are many tributaries and gullies, which are distributed in veins on both sides of the river. Gullies and valleys are typical V-shaped, which are blocked by debris flow fan-shaped deposits and some fjords on both sides of the river, and some reach forms intermountain basins and U-shaped valleys. Due to the development of collapse, landslide and debris flow, boulders and boulders on the riverbed are row upon row, fluctuating and silting is very serious [4]. 1.3.3 geological structure Tengchong area is located in the west of Lushui-Ruili fault, near the junction of India and Eurasia plate, and belongs to the south of Boshulaling-Gaoligongshan fold belt of Gangdise-Nyainqentanglha fold system. It is famous for its developed fault structure, young active volcano, strong geothermal and seismic activity [3]. Most of the area is occupied by migmatite and granite, and the remaining upper Paleozoic shallow metamorphic rocks are scattered in acidic intrusions. Neogene and Quaternary are distributed along Longchuan River, Daying River and Binglang River, and intermediate-basic volcanic rocks cover most areas. Affected by fault activity, earthquake activity and geothermal activity, the strata in this area are very broken and loose, and are easily weathered, which provides sufficient material basis for the development of landslides and debris flows. The survey results show that the thinnest part of the weathered layer is10m, and the thickest part is over100m. Most of the landslides and mudslides caused by 7. 19 disasters, such as those in Yongxing Village, Shangjie Village, Bajiaoling Landslide and Gaotian Village in Zhonghe Township, develop along the weathered layer. The neotectonic movement in the study area is very strong, which is characterized by strong and frequent seismic activity, extensive exposure of hot springs, uplift of mountains and subsidence of basins, providing sufficient material basis and energy conditions for the development of landslides and debris flows [4]. 2. Characteristics of landslide and debris flow disaster 2. 1 Sudden outbreak and rapid disaster caused Tengchong 7. 19 landslide and debris flow flash flood disaster. On July 17- 19, the rainstorm broke out suddenly, with high intensity and long duration, and the rainfall was concentrated in the northern mountainous area. In addition, the rainstorm occurred in the middle of the night, with heavy rainfall in the early stage. The mountain is high and steep, the slope is short and the river is short. 2.2 A disaster chain is formed, and disasters extend from mountainous areas to mountainous plains. This disaster is caused by a rainstorm, and its disaster process is as follows: firstly, collapse, landslide and slope debris flow are formed in the upper reaches of the valley and on the hillside; Under the erosion of slope runoff, some landslides and collapses are directly transformed into slope debris flow, and some of them are piled up in the toe of slope and channel together with slope debris flow, forming gully debris flow in torrential flood erosion; After the debris flow leaves the ditch, it forms a flood with high sediment concentration with the mainstream flood, carrying a lot of driftwood and stones to the downstream of the river. Therefore, the disaster of rainstorm-landslide-debris flow-mountain torrent-driftwood flow-flood with high sediment concentration has formed a disaster chain, which extends from mountainous area to the foot of slope, from mountainous area to Pingba area, and from mountain village to town. 2.3 The hazard scope is concentrated and the area is obvious. Due to the concentrated scope and strong locality of this rainstorm, the disaster and harm only occurred in seven towns in the northwest of Tengchong County and three towns in Yingjiang, including seven towns in Houqiao Town, such as Yongxing Village, Qingkou Village, Dongcun Village and Shangjie Village, among which Gaotian Township, Dacun Township and Mingguang Township, Diantan Town and Gudong Town in Zhonghe Township were the most seriously affected, and other towns in the east and south were also affected. 2.4 The number of disasters is large, the scale is small, the single disaster is strong, and the casualties and property losses are heavy. According to the field investigation, there are thousands of landslides and mudslides caused by heavy rain in the northern part of Tengchong, of which 100 poses a threat and causes harm.

Most of them are small in scale, and the volume of landslides and debris flows are mostly tens to hundreds of cubic meters, and most of them are located outside residential areas and farmland, which has not caused serious disasters. However, the scale of several landslides and debris flows that caused disasters is relatively large, mostly in the order of 1000m3, while the volume of Gaotian landslide is 2.00× 1.05 m3. Because of its large scale, it is extremely destructive after sliding, posing a serious threat to roads and villages. 2.5 Low outbreak frequency According to the local elderly, during July and August of 1946, serious rainstorm, landslide and debris flow occurred in Monkey Bridge and neighboring zhina, and many villages were moved down from the mountain after that disaster; 1952, a large-scale landslide occurred near Xiaoshuijing in Houqiao Town, killing 7 people. The disasters around 1975 and after 1984 are serious, but the scale and disaster losses are far less than those in July 2004.19. In the 58 years since 1946, we have never seen such heavy rain. It can be seen that the frequency of 7. 19 debris flow disaster can be regarded as once in 60 years, with extremely low frequency, which is rare in history. 3 Prediction of the development trend of landslide and debris flow disasters 200 1 year ago, 302 landslides, debris flows, unstable slopes, collapses and geological disasters in mine goaf were discovered in the county [3]. After 1999, the precipitation was obviously too much, and then the landslide and debris flow activities in Rehai and other places were strong, and the geological disasters tended to be active, which brought serious threats to local villages and towns, tourist facilities and rural cities. Since July, 2004, the continuous rainstorm has caused thousands of landslides and mudslides in Tengchong, with more than 100 disaster spots, and 25 places have seriously threatened the lives and property of more than 5,000 households 1000, causing serious harm to towns, counties, farmland, irrigation canals and highways. The disaster was controlled by the rainstorm center, all of which occurred in the central and northern regions, and the previous disaster was relatively light, while the middle and lower reaches of Longchuan River in the south, which had serious geological disasters, did not have serious disasters this time. This shows that under the conditions of geology, topography and solid matter, rainstorm has become the most important stimulating factor of landslide and debris flow disasters. 7. After the19 disaster, in addition to the geological disasters directly caused by the above seven towns and villages, it also caused a large number of potential landslides and collapses, destroyed forest vegetation, shattered slopes, made a large number of slopes unstable, formed many free surfaces and tensile cracks, and many large-scale old landslides were revived one after another. The disaster area is also the local rainstorm center, and the rainstorm is very frequent. Once a rainstorm occurs, it will induce a series of geological disasters and form a disaster chain. The investigation shows that the occurrence of 7. 19 disaster has opened the curtain of a new round of geological disaster activities in Tengchong County. In addition to this disaster area, other areas have also induced new disasters. For example, a large number of landslides are in the creeping stage, some are in the critical state before sliding, and debris flows are rich in loose solid substances. Therefore, in the future, under the excitation of external factors such as disastrous rainstorm or earthquake, landslides and debris flows will gradually become active, and their harm to human life and property and mountain environment will be further intensified, and the losses caused by disasters will be further expanded. The situation of disaster prevention and mitigation is very grim. 4 Current emergency disaster reduction measures 4. 1 Strictly investigate the hidden dangers of disasters and transfer people and property in areas with serious hidden dangers in time. At present, in addition to strengthening the disaster relief, resettlement and dynamic monitoring of existing disasters and hidden dangers, we should also widely mobilize the masses and the vast number of geological disaster monitoring and alarm personnel and professionals to investigate the hidden dangers of geological disasters in towns and villages, find out the distribution, harm scope and degree, development trend of disasters, and master the overall situation of disasters. For serious hidden danger points that can't be implemented temporarily, transfer personnel and property in time to reduce losses caused by disasters [5]. 4.2 Making emergency plans for sudden disasters 7. 19 The occurrence of disasters has sounded the alarm for governments and competent departments at all levels. In view of the severe geological disaster situation, it is necessary to set up a disaster emergency leading group, formulate an emergency plan for sudden geological disasters, and make careful and reliable plans for people's escape routes before the disaster, resettlement sites, post-disaster rescue and disaster relief, fund raising, personnel evacuation, traffic security, material transportation, resettlement of victims, health and epidemic prevention, and communication transmission. Once a disaster occurs, it should be implemented in accordance with the formulated emergency plan to ensure foolproof and orderly progress. 4.3 timely 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 distinguish the signs of geological disasters, how to escape, avoid disasters, rescue and choose temporary and safe residences after disasters. Work together, brainstorm, give full play to and mobilize the enthusiasm of the masses for disaster prevention and relief, minimize casualties and property losses, and fully implement the "people-oriented" disaster reduction purpose. 4.4 Strengthen the monitoring, early warning and forecasting of disaster sites 7. 19 Before the disaster occurred, the land department of Tengchong County cooperated with the meteorological department to make a disaster forecast. According to the monitoring and forecast, people in many disaster danger areas were evacuated in time, thus avoiding greater disaster losses. Monitoring, forecasting and early warning have played a very important role in disaster reduction and prevention. Therefore, it is necessary to continue to strengthen the monitoring of landslide and debris flow disaster points that potentially threaten and endanger people's lives and property during the flood season, and make predictions in combination with meteorological forecasts and various signs of disaster activities. 4.5 Do a good job in emergency disaster assessment in the resettlement areas for victims. 7. 19 After the disaster, the reconstruction and resettlement of the disaster area is the most urgent problem for the cadres and masses in the disaster area. For places that need to resettle victims, it is necessary to do a good job in geological disaster investigation and risk emergency assessment, and try to avoid construction in disaster-prone areas. In the investigation, it was found that some villagers built new houses on unsafe high and steep slopes. Therefore, land and rural cadres should strengthen the supervision of new houses built by the victims, and it is strictly forbidden to dig and fill them indiscriminately when building sidewalks, restoring destroyed roads, canals and reclaiming farmland. 4.6 Construction of emergency disaster reduction projects to improve disaster prevention and resilience. For the landslide that is in the creep period and critical state at present, the cracks should be blocked in time, and at the same time, the surrounding and slope water should be led out of the landslide body to prevent water from infiltrating into the slope body; For the paddy field on the landslide, the irrigation amount should be reduced to prevent the water body from infiltrating; For steep slopes and dangerous trees, slope cutting is appropriate to clear obstacles [4]. For mudslides and flash floods that endanger villages and towns, temporary drainage works such as lead gabion diversion dikes and dry-built retaining walls should be built to prevent mudslides and floods from overflowing. At the same time, clean up narrow river valley sections, culverts, bridges and buildings that hinder flood discharge, and dredge river ditches. 5. Disaster prevention and mitigation measures 5. 1 Detailed investigation and activity evaluation of mountain disasters 7. 19 After the disaster, there were thousands of new disaster points in Tengchong County, and the number, distribution area and activity state 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 law, harm degree and future development trend of disasters, so as to provide basis for disaster zoning, risk assessment, monitoring and prevention in the future. 5.2 Mountain disaster risk analysis and zoning is a regional prediction of disasters, which can provide guidance for local urban and rural construction, highway, water conservancy, farmland planning and disaster prevention [6]. On the basis of detailed investigation of regional geological disasters, it is very important to classify and partition according to the influencing factors of disasters (distribution density, height difference, slope, lithology, structure, earthquake, rainstorm, forest vegetation, etc.). ) and the severity of future dangerous areas. 5.3 Systematically carry out mountain disaster control. For disaster points that seriously threaten towns, factories and mines, important water conservancy and electric power facilities and large residential areas, it is necessary to carry out planning suggestions, feasibility studies and project initiation of disaster prevention projects as soon as possible, and implement project management in stages according to priorities. In addition, strengthening the restoration and protection of forest vegetation in disaster areas and doing a good job in soil and water conservation will also play a very important role in reducing the occurrence of landslides, mudslides and flash floods and reducing the degree of disasters [6]. 5.4 Establishing a Mountain Disaster Prediction and Early Warning System Because geological disasters are widespread and mostly located in remote mountainous areas, the existing meteorological and hydrological stations and disaster monitoring stations cannot meet the needs of forecasting. Therefore, a monitoring and forecasting system for geological disasters should be established as soon as possible, such as monitoring rainfall in real time by telemetering rain gauge and weather radar, and monitoring landslide displacement and deformation by GPS. 5.5 Strengthening departmental cooperation and building a disaster prevention platform Monitoring, forecasting and prevention of landslides, mudslides and mountain torrents is a complex systematic project, involving not only the departments of land and resources, but also the departments of administration, water conservancy, hydrology, meteorology, earthquake and disaster relief. Therefore, the leaders in charge should coordinate all departments to build a mountain disaster prevention platform, realize resource sharing and information exchange, and improve the overall defense capability of mountain disasters.