Discussion on design analysis of debris flow disaster reduction and control project?

According to incomplete statistics, the distribution area of debris flow disasters in China accounts for about half of the whole country, but the GDP created in this area is less than 1/3 of the whole country. Compared with the national average, the per capita GDP is also far from the national average. Every year, the economic losses caused by mudslides and landslides are about 654.38+0 billion, and more than 900 people die, which has a serious impact on the development of the vast mountainous areas. The prevention and control of debris flow and landslide has become an important guarantee to realize the harmonious and effective development between man and nature, regional progress and development, especially the strategy of developing the western region.

2 case studies

The debris flow of Zhiren River in Adong Village is located on the west side of the residence of Adong Village Committee in Shengping Town, Deqin County, Yunnan Province, with a drainage area of about 30.56km2, a main ditch length of about 12.04km, a relative height difference of 2200m and an average longitudinal slope of 158‰. Gullies are mostly V-shaped, with steep bank slopes on both banks. The project area belongs to the cold temperate plateau climate, with distinct dry and wet seasons and obvious vertical zoning, and the rainfall increases with the elevation. Under the influence of mountain monsoon climate and the uplift of Yunling mountain range, a single-point rainstorm often forms in the upper reaches of the basin, which then turns into a torrent, providing powerful hydrodynamic conditions for the formation of debris flow. Affected by geological structure, stratum lithology, adverse geological processes and human engineering activities, the loose solid sources of debris flow are mainly landslide source, slope erosion source and gully bed exposed source. The gully landform of debris flow basin is obvious, and loose material sources are mainly accumulated on bank slopes and river beds. Its solid source is mainly provided by landslide and weathered slope erosion; Debris flow is formed under the excitation of heavy rain; The fluid is mainly composed of sand, gravel, rubble and cohesive soil, which is thick porridge; The time interval of its large-scale eruption is more than 10 years, and a smaller eruption will occur every 5 years or so. During the development of rainstorm in the valley, debris flow is classified as medium frequency viscous debris flow. The debris flow gully area is affected by the Lancang River fault and Jinsha River fault, and the ice in the upper reaches of the basin is strongly weathered and the rock mass is broken. Under the influence of unfavorable weather and earthquake, several large landslides in this area still have the possibility of further activities. In addition, the upper reaches of the basin near the watershed have been weathered by ice for a long time, which has also produced a continuous source of materials. Debris flow gully will not stop its activity for a long time, and may erupt again under the influence of heavy rain or earthquake, provided that sufficient water or material sources are provided.

3 Overview of Debris Flow in China

At present, there is not an accurate number of debris flows in China. According to incomplete statistics, there are hundreds of thousands of mudslides in China, old and new, large and small, inactive and active. There are tens of thousands of debris flow gullies, only distributed in the upper reaches of the Yangtze River, and 6,543,800 landslides have been basically identified. There are more than 65,438+500,000 debris flow gullies with a length of 65,438+500,000 km. It poses a great threat to the property and life safety of 20 million people in more than 400 towns and villages in more than 200 counties.

4 Current situation of debris flow prevention and control

Although the prevention and control of debris flow in China has made gratifying achievements. However, with the increasing demand for disaster reduction brought by social and economic progress, there are still many problems in the current prevention and control of mudslides and landslides: 4. 1, monitoring and forecasting of mudslides. Meteorological rainfall stations play a key role in the prevention and control of debris flow disasters. However, in terms of layout, it is still sparse in the east and sparse in the west, with many plain areas and relatively few debris flow disaster-prone areas. Debris flow monitoring in China is still in its infancy, and some technical problems have not been completely solved. Therefore, the demand of debris flow in disaster monitoring and early warning, disaster reduction and prevention is far from being satisfied. 4.2 The layout of monitoring points is unreasonable. Most of the debris flow monitoring points in China are located in the upper reaches of the Yangtze River, and they were all set around the 1990s, lacking unified command and planning. In some provinces with serious mudslides, such as Henan and Liaoning, the monitoring of mudslides is very weak. 4.3 Monitoring equipment and methods are still relatively backward. At present, China's monitoring and early warning technology and analysis and processing methods are relatively backward, and there are a large number of local methods, which makes the actual demand far from being satisfied. Compared with automation and real-time monitoring in Europe, America, Japan and many other advanced countries, there is still a big gap. 4.4 There is no unified network, which makes it impossible to enjoy resources. At present, most of the existing debris flow monitoring positions belong to river basin units or provincial water administrative units, and some of them are managed by land-related resources institutions, lacking a unified network, making it difficult to share information. 4.5 The communication mode is still relatively backward. The transmission of information and data from county to station is realized by various means, such as optical fiber dedicated line, mobile phone, fixed phone, Internet and fax. However, most monitoring stations and county-level stations rely on low-standard wired communication, and their communication is difficult to be effectively guaranteed under bad weather conditions. 4.6 The prediction of debris flow disaster is still in the experimental stage. Due to the lack of sufficient understanding of the quantitative relationship between debris flow and rainfall, there is a lack of understanding of weather system, rainfall process and rainfall. There is a lack of data collection of critical rainfall, and there are no plans and measures to accurately predict debris flow disasters. At present, only the weather forecast is used for preliminary forecast.

5 Debris flow prevention measures

According to the policy of putting prevention first and combining prevention with control, the state and local governments invest a lot of money every year to control mudslides, which greatly reduces the losses caused by disasters. Moreover, the comprehensive prevention technology combining civil engineering and ecological engineering has been developed, and different disaster prevention methods have been formed for different protected objects, such as urban debris flow prevention methods, highway debris flow prevention methods, and mine debris flow prevention methods. The key and characteristic work includes the following aspects: (1) Focusing on the construction of national large-scale water conservancy and transportation energy projects, a large number of debris flow control work has been carried out in a targeted manner, effectively ensuring the normal operation of national key construction projects. Just like the disaster management in the Three Gorges reservoir area, the areas where a large number of mudslides often occur in China have been comprehensively managed and achieved obvious social benefits. (2) The Ministry of Water Resources and government units at all levels should participate in the task of soil and water conservation in hilly areas. In recent years, the cumulative soil erosion control area is equivalent to millions of small water conservancy projects, and these soil and water conservation schemes have a vital impact on reducing debris flow disasters. (3) Establish a disaster emergency information transmission system. These systems cover the monitoring system, and the debris flow monitoring and early warning system is set in cities with convenient transportation. The central control station implements disaster consultation, information collection and comprehensive analysis; Set up a first-class station in each typical road section, responsible for disaster treatment, information integration, alarm release and other aspects of this road section; Set up basic observation stations in each class, collect information from observation points, report the disaster situation and take emergency measures; An observation point is set at each disaster point, and comprehensive observation points are set at key disaster points to collect observation point information data on both sides of the upstream and downstream and along the river basin as a node of the disaster monitoring network. There is also a monitoring system management operation mode, and the debris flow monitoring and early warning system should be managed by the local transportation unit, and be responsible for relevant liaison and guidance to the first-class station business; The first-level station is directly led by the location of the central station and needs to be responsible for disaster early warning and emergency rescue in their respective sections.

6 prevention and control of debris flow

6. 1 Strengthen the construction of laws and regulations. Formulate relevant laws and regulations on the prevention and control of debris flow disasters as soon as possible, standardize the production and life of the public with corresponding laws and regulations, and prevent unreasonable human activities from aggravating or causing disasters. 6.2 Strengthen basic work. Using the methods and technologies such as database, remote sensing technology and computer, a nationwide investigation and study of debris flow disasters was carried out, and an information system of debris flow disasters was established. It can effectively share information and data, and provide scientific basis for formulating disaster reduction plans and implementing disaster prediction in related regions. 6.3 Strengthen the construction of debris flow forecasting and early warning system. Referring to the early warning system of debris flow and landslide in the upper reaches of the Yangtze River, a complete monitoring and communication early warning system was established, which effectively improved the forecasting level. It is also necessary to establish and improve a county-centered and village-based group monitoring and prevention system to minimize the losses caused by disasters. 6.4 Strengthen scientific research and popular science education on debris flow disasters. Strengthen the research and analysis of practical technologies such as debris flow disaster monitoring, forecasting and forecasting. It is also necessary to widely popularize and publicize the basic and disaster prevention knowledge, so that the concept of disaster prevention and mitigation of the whole people can be effectively improved. 6.5 Formulate unified national standards. Due to the lack of information and data related to debris flow and landslide disasters, and the unified criteria for disaster monitoring, statistics, disaster assessment and early warning, it is difficult to enjoy information and data. The real-time performance of disaster assessment and monitoring system is relatively poor, which brings great problems to disaster prevention and control, so it is necessary to formulate a unified national standard. 6.6 Establish and improve the debris flow risk assessment system for construction land. In the planning and construction of mountainous towns, disaster risk and possibility assessment should be carried out, and disaster prevention and relief systems at all levels should be established and improved. For the emergency rescue system, make relevant improvements and formulate mutual disaster plans and measures. In areas with frequent disasters and difficult governance, people in dangerous areas should be transferred to safe areas by means of relocation and avoidance. 6.7 Establish a diversified investment mechanism for debris flow prevention and control. Strengthen the investment of local units and national governments in relevant aspects, introduce relevant incentives and preferential policies, extensively absorb social funds, and form a multi-level and multi-channel investment system. 6.8 Strengthen the pilot project of debris flow prevention and control. According to the causes of disasters and environmental conditions, select representative small watersheds to implement pilot treatment, explore corresponding prevention experience, gradually expand the pilot scope, and comprehensively promote the prevention and control of mudslides and landslides. It is necessary not only to strengthen the monitoring and early warning of key projects and disaster points that pose a greater threat to residential areas, but also to implement project management, strengthen project construction management, and reduce the disasters caused by human activities on the environment.

7 concluding remarks

Debris flow control is a major event closely related to people's livelihood, so it is necessary for our engineering practitioners to actively pay attention to related engineering work. Only on the basis of joint efforts from all walks of life can we better nip in the bud and manage it in an orderly, effective and economical way.

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