Traditional Culture Encyclopedia - Weather forecast - Analysis on the development trend of geological disasters

Analysis on the development trend of geological disasters

According to the above survey statistics and analysis data, we can see that:

During the period from 1983 to192, there were 30,569 landslides, collapses and mudslides in China, with an average of 569 per year, resulting in 529 deaths and disappearances (Duan et al.,1993); From 1995 to 2003, there were 669 13 landslides, collapses and mudslides, with an average of 7435 per year, resulting in 1 168 deaths and disappearances;

1992 There were 45 cities or regions with land subsidence, with a subsidence area of 48655km2;; By 2002, the number of land subsidence cities or regions in China had increased to 82, with the subsidence area exceeding 64,000 square kilometers.

At the same time, in the past 50 years, especially in the 1980s and 1990s, the number of large-scale and extra-large geological disasters has been increasing (Figure 2.20).

Figure 2.20 Statistics on the relationship between the number and time of large and extra-large geological disasters in China in the 20th century.

Combined with the above situation and China's economic and social development, the development of human engineering activities, natural climate and earthquake changes. We can make analogical reasoning and make a preliminary analysis of the development trend of geological disasters. In this regard, the following points can be drawn:

(1) Unreasonable human engineering activities aggravate geological disasters.

As mentioned above, unreasonable human engineering activities are one of the main factors inducing geological disasters. In recent years, the geological disasters caused by this have accounted for more than 50% of the total number of geological disasters in China. These activities are mainly mining activities, slope cutting and cutting in road and construction projects, water conservancy facilities and farmland irrigation on slopes. In 2002, 83% of the major geological disasters in Guangdong were induced by human activities, and the number of geological disaster deaths accounted for 54% of the total number of geological disaster deaths in the province. Among them, the geological disasters induced by quarrying and mining account for 50% of the total geological disasters induced by human activities. In 2002, 82% of the major geological disasters in Fujian were induced by human activities, and 94% of them were induced by cutting slopes to build houses.

As one of the important national infrastructures, the construction of road traffic facilities is an important factor causing landslides, collapses and mudslides. Because the construction of these projects in mountainous areas is often accompanied by large-scale earthwork excavation, a large number of high and steep slopes are formed, which reduces the stability of the mountain, and then leads to landslides, collapses and mudslides. Therefore, landslides, collapses and mudslides often occur along highways and railways in mountainous areas. During the construction of medium-sized railways such as Baocheng, Baolan, Cheng Kun, Nankun and Dongbao, landslides and collapses occurred to varying degrees. Almost 50% or even 70% of geological disasters along the railway are caused by excavation. According to the investigation of the Ministry of Geology and Minerals 1986 to 1987, there are 266 landslides and 50 1 collapses in baoji-chengdu railway. China's transportation has developed rapidly. 1998 to 2002, the mileage of new railways, new highways and new expressways were 5944 km, 202,000 km and 1.75 million km respectively. Among them, the mileage growth rates of railways and highways are 1486km and 50594km respectively (Table 2. 10). With the continuous development of railway and highway construction, more landslides, collapses and mudslides will occur in mountainous and hilly areas.

Table 2. 10 Main production capacity newly added in national road traffic construction in recent five years: km

(2) The disorderly exploitation of mineral resources and the increasing exploitation will aggravate the deterioration of geological disasters.

Over the years, China's national economy has been growing rapidly and steadily, with GDP of 1970, 1980, 1990 and 2002 being 225.3 billion yuan, 451800 million yuan and 654.38 billion yuan respectively. Economic growth is always accompanied by resource consumption and environmental destruction. From 1990 to 200 1, China's oil consumption increased by 100%, natural gas by 92%, steel by 143%, copper by 189%, aluminum by 380% and zinc by 3/kloc. In the process of resource development and environmental transformation, man-made geological disasters are always accompanied. Open-pit mining causes collapse, landslide and debris flow, while underground mining causes ground subsidence, ground subsidence and ground fissures.

The contradiction between the decrease of groundwater and the increase of water consumption will further aggravate the land subsidence and ground fissure disasters. The new round of national groundwater resources evaluation results show that groundwater resources in northern and plain areas of China are decreasing. In the 20 years since 1984, the exploitable groundwater in northern and plain areas has decreased by 5.6 billion m3 and 30.9 billion m3 respectively. However, in recent 20 years, the national water consumption has increased sharply, and the amount of groundwater exploitation has increased at an average annual rate of 2.5 billion m3. At present, groundwater in a considerable part of northern China is over-exploited, including the whole Hebei Province, and groundwater in some large and medium-sized cities such as Beijing, Tianjin, Hohhot, Shenyang, Harbin, Jinan, Taiyuan and Zhengzhou has been over-exploited or seriously over-exploited. At present, more than 300 cities in China are short of water to varying degrees. Overexploitation of groundwater and the general decline of groundwater level are the main factors inducing land subsidence and ground fissures. At least 40 cities in China have caused land subsidence due to unreasonable exploitation of groundwater. In Hebei Plain and Xi 'an, Datong and Suzhou-Wuxi-Changzhou areas, over-exploitation of groundwater has also led to ground fissure disasters. It is predicted that by 2030, the annual demand of groundwater in China will reach 78 1 100 million m3, and the annual gap will exceed 1 100 million m3. The decrease of groundwater and the increase of water consumption will inevitably lead to over-exploitation of groundwater. If we continue to overexploit groundwater, the land subsidence and ground fissure disasters in the above areas will be further aggravated.

(3) The development of urbanization intensifies geological disasters.

Cities are areas where population and human engineering activities are very concentrated. With the acceleration of urbanization in China, geological disasters caused by unreasonable man-made engineering activities in cities and towns will become more and more prominent. Many mountainous cities in China, such as Chongqing, Lanzhou, Dalian, Shiyan and Panzhihua. Due to the unlimited expansion of the city and the construction of cities in mountainous areas, it has become a city with serious landslides and collapses, which has seriously damaged the natural balance in mountainous areas. In order to meet the needs of development, water consumption in plain cities is increasing, and then groundwater is over-exploited. More than 50 cities caused land subsidence. China is in the transitional stage from the traditional agricultural society to the modern society, and has entered the accelerated stage of urbanization. From 1978 to 2003, the number of cities in China increased from 193 to 688, the number of established towns increased from 2 173 to 2003 12, and the total urban population increased from1700,000 to 456 million, accounting for/kl. It is predicted that by 20 10, the proportion of urban population in China will increase to 45%, and by the middle of 2 10 billion ~ 1000, it will reach 60% ~ 70%, and the number of cities in China will exceed1000, with a population. It is estimated that by 2050, an average of120,000 people will move from rural areas to cities every year, and the state will invest 800-900 billion yuan in urban infrastructure construction every year to meet the requirements of urbanization. With the rapid development of China's economic construction, Beijing, Tianjin, Shanghai, Guangzhou, Hangzhou, Nanjing and other major cities in eastern China have entered a new period of large-scale re-planning. During the Tenth Five-Year Plan period, Guangzhou, Tianjin, Beijing, Nanjing, Shenzhen, Shenyang, Hangzhou, Shanghai, Harbin and Qingdao spent 200 billion yuan on subway and rail transit construction. With the implementation of China's western development strategy, a number of cities along the Qinghai-Tibet Railway and the Eurasian Continental Bridge will be built and expanded, and they are also facing the problem of increasing geological disasters.

Therefore, it can be considered that with the development of cities, land subsidence disasters and ground fissure disasters caused by over-exploitation of groundwater in plain areas and inland basins will intensify; In mountainous and hilly areas, under the combined action of building, mining, road construction and rainfall, landslides, collapses, mudslides and ground collapses will also show an increasing trend.

(4) The western development will aggravate geological disasters.

It is an important strategic decision made by the CPC Central Committee to implement the strategy of developing the western region and accelerate the economic development in the western region. However, the western region, with its fragile natural environment and complex geological structure, is the region with the most kinds of geological disasters and the strongest activities. Remote sensing data show that millions of collapses, landslides and mudslides are widely distributed in western provinces (autonomous regions and municipalities). According to the disaster statistics over the years, western provinces such as Sichuan, Chongqing, Yunnan, Guizhou, Shaanxi and Gansu have always been the most economically developed and severely affected areas in China, and some areas in Xinjiang, Tibet and Qinghai are also very serious. The Tianlan Railway, baoji-chengdu railway, chengdu-kunming railway and the water conservancy projects in the upper reaches of the Yellow River and the Yangtze River in the western region have also suffered serious collapses, landslides, mudslides and other disasters. The development of the western region involves many fields, among which resource development and infrastructure construction are the key points. During the Tenth Five-Year Plan period, the capital investment in large and medium-sized projects of the western railway is expected to reach 654.38+0.8 billion yuan, and by 2005, the western railway is expected to reach 654.38+0.8 million kilometers. These economic activities will have an important impact on the ecological environment and geological disasters, which may lead to further deterioration of resources and environment and rapid development of geological disasters.

(5) Changes in natural conditions aggravate geological disasters.

1) Climate change and geological disasters. Heavy rain or continuous rainfall is the main factor inducing geological disasters. Statistical analysis in recent years shows that sudden geological disasters caused by rainfall account for 63% in China, of which sudden geological disasters caused by heavy rain account for more than 66%. Moreover, the occurrence of sudden geological disasters is positively related to the annual and seasonal changes of rainfall, that is, the occurrence of sudden geological disasters in flood season accounts for more than 60% of the whole year, and the year with high rainfall is also the year with frequent geological disasters.

The climate of the earth is constantly changing. The observation records and research predictions of meteorological system show that the average temperature of global land and ocean surface has been on the rise since 196 1, and it rose by about 0.6℃ in the 20th century. According to the third assessment report completed by the Intergovernmental Panel on Climate Change in 20001year, according to 35 scenarios of greenhouse gas and aerosol emissions during the period of 1990 ~ 2 100, it is predicted that the global average surface temperature will rise by 2 100 compared with 1990. After global warming, not only the average climate will change, but also the frequency of extreme events in which weather and climate seriously deviate from the average state will change. The observation records also show that there is an increasing trend of heavy rain and extreme precipitation events in the middle and high latitudes of the northern hemisphere.

The increase of rainstorm and extreme precipitation events will lead to the intensification of geological disasters such as landslides, collapses and mudslides. Because heavy rain and extreme rainfall are the most likely to induce large-scale group landslides, collapses and mudslides, and often cause very serious consequences. For example, in Sanming City, Fujian Province, landslides, collapses and mudslides rarely occurred in history. However, on June 16, 2002, the area suffered from once-in-a-century heavy rainfall, and landslides and mudslides occurred in five counties, including Jianning, Jiangle and Ninghua, resulting in 40 deaths and property losses of/kloc-0.2 billion yuan. From July to September, 2002, Lianshan, Shenzhen, Xinyi, Wengyuan, Lechang, Wuhua and other counties (cities) in Guangdong Province were hit by a once-in-a-century rainstorm, which triggered landslides, collapses and mudslides, resulting in 42 deaths and property losses of 360 million yuan. From June 18 to June 19, 2006, due to the continuous rainstorm, Suining County, Shaoyang City, Hunan Province suffered serious landslides, collapses and mudslides, and 12 townships in the county were affected, with the affected area reaching 1 12km2 and the affected population reaching 2/2. In 2002, there was continuous rainfall in Yili, Xinjiang, the duration and amount of which exceeded the historical extreme value, resulting in 9 counties (cities) 196 landslides and mudslides. A large number of facts have proved that China and other parts of the world are in a period of drastic climate change, and droughts, floods and storms will become more frequent. Therefore, geological disasters such as collapse, landslide and debris flow will become more active.

In addition, atmospheric precipitation has periodic dry and abundant changes. Since 1990s, precipitation in most parts of northern China has been a dry year. After entering the 20th century, the drought period will come to an end, and some parts of northern China will enter a period of abundant precipitation, and the precipitation will increase significantly compared with the previous decade. Under the influence of increased precipitation and enhanced hydrodynamic conditions, with the change of precipitation, the frequency of geological disasters in parts of northern China will gradually increase.

2) Earthquake activities and geological disasters. Seismic activity is an important factor affecting sudden geological disasters. China is the country with the most frequent and intense earthquake activity in mainland China in the world. On the whole, the earthquake activity has the characteristics of high frequency, high intensity, wide distribution, wide influence and obvious regional differences (Liu Jiang et al., 200 1). At present, there are 4 1% of the country's land area, more than 7 1% of provincial capitals and municipalities directly under the central government, and 120 cities with a population of more than 500,000, which are located in high-intensity areas with basic intensity of VII and above. Earthquake activities make the rock strata broken, the mountain unstable and the loose solid matter increase, which leads to landslides, collapses and mudslides. For example,1February 6, 1973, an earthquake of magnitude 7.9 occurred in Ganzi Prefecture, Sichuan Province, which triggered the 137 landslide. It is predicted that the earthquake activity in China is still active at the beginning of 2 1 century. Therefore, earthquake-induced geological disasters will also be very frequent in the western, northern and eastern coastal areas.

To sum up, the characteristics of human activities and climate change have promoted the increase of the frequency and density of geological disasters. However, in recent years, the whole country has intensified the propaganda and prevention of geological disasters, promulgated the Regulations on the Prevention and Control of Geological Disasters, established the monitoring and prevention system of geological disasters, and carried out the forecast and early warning of geological disasters in flood season, which has obviously enhanced the awareness of disaster prevention and mitigation of governments at all levels and the people. Therefore, the casualties caused by geological disasters have been controlled to a certain extent. However, with the development of social economy, the value of national and social assets will be higher and higher, and the distribution density of various infrastructures and buildings will become larger and larger, so the economic losses caused by geological disasters may still show a certain growth trend. With the substantial improvement of people's living standards, people will pay more attention to life and health, so the psychological and social impact caused by geological disasters of the same degree will be more serious.