1. Geographical distribution characteristics of geological disasters in China.
The geographical distribution of geological disasters in China is strictly controlled by the geotectonics of China. There are two zones in the hardest hit areas of geological disasters in the world, one is the Pacific Rim; The other is the Mediterranean. China is located in the circum-Pacific belt, and it is also the kink belt of the Mediterranean and Pacific belts. Specifically, China is located in the compression triangle of Indian plate, Pacific plate and Mongolian plate. Under the pressure of these three plates, Chinese mainland has formed two active crustal belts: the north-south belt and the east-west belt, which are often mentioned. In fact, the north-south belt is Y-shaped, and the east-west belt is NE-oriented. Under the control of this big outline, the strong earthquake area, strong landslide area and strong debris flow area in China are all distributed in this belt. The geological disasters in this area are more serious than those in other countries and regions in the world. The geological disasters in China are really serious. The eastern part of China is not monolithic, but broken plots. Its internal ups and downs, ups and downs, control the occurrence and development of geological disasters in this area; It also controls the occurrence and development of other natural disasters in this area. For example, floods, people only think that floods are caused by hydrological factors, but in fact, flood areas are mainly controlled by geological structural factors. The current flood areas are all modern crustal subsidence zones. At present, the flood control countermeasures are to build dikes to block water, and treat the symptoms rather than the root cause. In fact, "running" is the sinking of the earth's crust. Blindly heightening the levee will lead to great disaster sooner or later. Therefore, the author thinks that flood control measures should also be considered from the geological point of view.
2. Analysis of geological disasters in China.
Here are a few examples, and then a brief analysis.
(1) Earthquake disaster: There are more than 4,000 recorded earthquakes in China's history, resulting in 346 casualties and more than 2.3 million deaths. The annual economic losses caused by earthquake disasters are about 65.438 billion to 2 billion yuan, and the number of deaths is about 2,000 to 3,000. The earthquake is particularly serious.
(2) Mountain disasters such as landslides and mudslides: China is a mountainous country, with mountains, plateaus and hills accounting for 69% of the land area. Rivers crisscross and valleys are widely distributed. Under the influence of crustal movement, atmosphere, earthquake and human activities, a large number of mountain disasters such as landslides and mudslides are produced every year. According to the statistics of Sichuan Province, during the five years from 198 1 to 1985, landslides caused by a rainstorm exceeded 1000 in 28 counties, and 100 in 4 counties, exceeding 20%. Yunnan, Guizhou, Shaanxi and Sichuan are the most frequent areas of landslides in China, and the situation is similar. There are 70 counties threatened by debris flow disasters in China. Within 1, 975 ~ 1, 984, 10 years, debris flows broke out in 18 provinces, cities and districts in China, killing 2 1.36 people and destroying farmland 65. Comprehensive analysis of existing statistical data, including geological disasters such as landslides, landslides, mudslides and land subsidence, has caused direct economic losses of 2 billion to 3 billion yuan every year.
(3) Catastrophic soil erosion: internationally, it is stipulated that soil erosion modulus exceeds 1 10,000 t/km2 as catastrophic soil erosion. There are 50,000 km2 in the loess hilly region of northwest China, and the slopes with a slope greater than 20 in the Yangtze River basin are all serious soil erosion areas. In addition, the cover thickness also has a great influence on soil erosion. For example, the thickness of the soil layer in the loess area of northwest China is tens to hundreds of meters, and soil erosion only causes the fertility of cultivated land to decrease; The soil layer in the upper reaches of the Yangtze River is extremely thin, only a few tens of centimeters to several meters. Soil erosion makes cultivated land barren and loses farming conditions. The economic losses caused by soil erosion on the slopes in the upper reaches of the Yangtze River amount to 2.5 billion yuan per year. The cultivated land area in Sichuan Province has reached11670,000 mu. In Yunxi County, Hubei Province, 40 natural villages had to emigrate because of slate land. This kind of disaster has also appeared in Guizhou and Yunnan.
(4) Sandstorm and desertification disasters: The area of sandstorm and desertification disasters in China is 654.38 0.509 million km2, accounting for 654.38 0.07.5% of the land area, mainly distributed in arid, semi-arid and semi-humid areas in northern China. In the past half century, the desertified land in China has expanded by 50,000 square kilometers. According to preliminary statistics, China loses 654.38+0.5 billion yuan each year due to sandstorms.
(5) Man-induced geological disasters: due to blind activities, human beings have induced a large number of geological disasters in the process of economic activities. The more concentrated the population, the more geological disasters induced by human beings. The eastern part of China has the most concentrated population and economy, with frequent human activities, and geological disasters induced by human activities are more common. We usually call it engineering geological disasters, such as mine construction, groundwater exploitation, traffic construction, oil exploitation and other human activities will induce geological disasters. This geological disaster, in terms of its single loss, is not large, but together, the figures are very considerable. Generally speaking, the loss of geological disasters induced by human activities in China is very huge, and it is estimated that the annual economic loss is about1~ 2 billion yuan. Generally speaking, there are still serious soil erosion and desertification in China. People often think that this is caused by climate, but in fact it is mainly induced by human activities.
Based on the above information, we get that the annual economic loss caused by geological disasters in China is about 90 ~11000 billion yuan (1989 statistics). This figure is equivalent to116 of the total loss of natural disasters in China, which is considerable. The main threats of geological disasters are in residential areas and projects. The loss caused by geological disasters is not instantaneous, but long-term, which threatens the survival of mankind.
There are two kinds of geological disasters, one is vivid, such as earthquakes; The other is silent, such as desertification and soil erosion. Vivid things are easy to be valued, and silent things are easy to be ignored. It is very serious to pay attention to the consequences of silent disasters. Natural disasters can be divided into three types according to the time scale of their occurrence: ① Sudden, occurring in a few minutes or hours; (2) moderate speed, which occurs in a few days or months; (3) Chronic, which occurs once every few years or decades or hundreds of years. For example, the Jin State in the Warring States Period in the northwest of China, which is now Shanxi Province, has lush trees and rich products. Now the vegetation is sparse and loess is everywhere, and the northern part of Shanxi is desolate. This is the result of chronic disasters caused by long-term vegetation destruction and soil erosion. Threatening the survival of our future generations, the problem is very serious. This is an overview of geological disasters in China.
3. Examples and benefits of disaster reduction
China has done some work in reducing geological disasters, mainly in four aspects:
(1) Prediction and prevention of engineering geological disasters, such as construction geological advance prediction, tunnel collapse monitoring prediction, coal mine water inrush prediction, coal and gas outburst prediction and various engineering geological disasters prediction.
(2) Natural geological disaster prediction, such as earthquake trend prediction, impending earthquake prediction, landslide prediction, etc.
(3) Prevention and control of geological disasters, such as Jibazi landslide prevention, Dongchuan debris flow prevention, railway sand fixation, soil and water conservation in seven provinces and cities, and Lianziya-Huanglashi geological disaster prevention.
(4) Disaster Relief Work After the founding of New China, our government has done a lot of work in disaster relief, so I won't list them one by one.
Summarizing the work done, it is not difficult to see that the economic benefits of geological disaster prevention and control achievements are enormous. Here are some examples to illustrate.
(1)1982 In July, a landslide occurred in Yunyang area of the Yangtze River, which hindered navigation for a long time. After three years, more than 80 million yuan has been invested in prevention and control, and the direct economic loss caused by landslide is estimated to be 10 million yuan, and the total loss is nearly 10 billion yuan. In order to prevent the slope from sliding, 3 million yuan was invested in slope treatment, and good results were achieved.
(2) In the early morning of June 1985, a large landslide of 20-30 million m3 occurred in Xintan, Zigui County, Yangtze River, of which 2.6 million m3 entered the river and stopped for 12 days. Due to the accurate forecast, no one was killed or injured, and the property loss was minimal. Without this accurate forecast, it is estimated that the direct economic loss may be around 87 million yuan. It is predicted that the investment will be about 2 million yuan. The economic benefit of this control is 1∶44.
(3) Debris flow in Dongchuan is a world-famous large-scale geological disaster, which poses a serious threat to the survival of more than 60,000 residents living in Dongchuan City. According to statistics, since the founding of New China, the losses caused by debris flow to Dongchuan City have reached several hundred million yuan. 1982 to 1985, Chengdu Institute of Geography, Chinese Academy of Sciences and Dongchuan City jointly conducted a survey, put forward a prevention and control plan, and began to implement prevention and control on 1986. 1July 5, 987, 30 years of rare rainstorm, no disaster. Now that the whole project has been completed, this city is praised as "Garden City" by Yunnan Province.
(4) Soil and water conservation in seven provinces and cities has also achieved remarkable economic benefits. Taking the experimental demonstration area of comprehensive management of Huangjiaercha small watershed in Xiji, Ningxia as an example, the land area of this area is 5.7km2, and the comprehensive management started at 1983. Taking grain output as an example, the output of 1982 was 23. 1kg, and that of 1990 was 120kg, an increase of 425.4%. Net output value of the whole basin: 1990 is 8. 1 times of 1982; The per capita income of 1990 can reach 73 1 yuan, which is 380.9% higher than that of 1982.
We should see that the prevention and control of geological disasters is long-term, benefiting not only today but also future generations. Generally speaking, the benefit of prevention and control of geological disasters can reach 1∶20, and the benefit of earthquake engineering can generally reach about 1∶ 10. The benefits of geological disaster prevention and control are very considerable. It can be said that disaster reduction means increasing production.
Generally speaking, the causes of geological disasters mainly come from three aspects: ① rainstorm and flood; ② Crustal movement; ③ Human activities. However, human activities can promote the intensification of the first two natural factors, with a wide range and a large amount. Human engineering activities often lead to a large number of engineering geological disasters. The prevention and control of geological disasters is an important disaster reduction measure. Generally speaking, the following measures are very important: ① It is urgent to raise the awareness of disaster reduction of the whole people, strengthen the popularization of science, and raise the awareness of disaster reduction of the whole people; (2) There should be investment and engineering measures. Without investment, it is impossible to reduce disasters and obtain benefits; ③ Establish the concept that the disaster reduction project is a "geological project". Unlike ordinary civil engineering, disaster reduction projects without geological foundation may lead to serious disaster consequences. The prevention and control of geological disasters in Lianziya can not be separated from geology, which provides an example for disaster reduction practice. (4) Environmental protection is the basic work to reduce geological disasters, and it is impossible to control and destroy while reducing disasters. This problem must be taken seriously.