The cause and harm of floods, water is one of the most useful resources on the earth. If the amount of water is large enough, it will become a flood. Flood is a very complicated disaster system, which will bring great harm to people. Let's look at the causes and harm of floods.
Causes and Hazards of Flood 1 Flood refers to the phenomenon that the water flow of rivers, lakes and oceans increases or the water level rises sharply due to heavy rain, snow melting, ice melting and dam failure of reservoirs. When the flood exceeds a certain limit, it will bring losses and disasters to human normal life and production activities, which is called flood disaster for short.
According to the different causes and geographical location, it is often divided into rainstorm flood, snowmelt flood, ice flood, flash flood and dam-break flood. Tsunamis and storm surges can also cause floods.
Among them, rainstorm and flood are caused by rainstorm. Summer rainfall is the most in most parts of China, and most of the flood water occurs at this time. A flash flood is a flood that suddenly surges down in a ravine. Due to the steep slope of mountain and river bed, runoff and confluence are faster after rainfall, forming a rapidly fluctuating flood peak.
Floods occur frequently, spread widely, are fierce and extremely destructive. The flood not only flooded houses and people, causing a large number of casualties, but also swept away the living environment including grain, flooded farmland, destroyed crops, and led to a sharp reduction in grain production, which led to famine. Floods will also destroy factories, communication and transportation facilities and cause serious damage to the national economy. In addition, there are a series of other disasters such as landslides, mudslides and epidemics.
flood prevention measure
1. According to the flood information provided by local TV, radio and other media, combined with their own location and conditions, calmly choose the best route to evacuate, so as to avoid the passive situation of "people come first and there is no water".
2, recognize the road signs, clear evacuation routes and destinations, to avoid going the wrong way because of panic.
4. Prepare enough fast food or cooked food for several days, and prepare enough drinking water and daily necessities.
5. Tie rafts and bamboo rafts, collect materials suitable for floating, such as wooden pots, wood, large pieces of foam plastic, etc., and process them into life-saving devices for emergencies.
6. Inconvenient valuables should be buried underground or placed in high places after waterproof binding. Small valuables such as tickets and jewelry can be sewn into clothes and carried around.
7. Keep communication equipment that can still be used.
The cause and harm of flood. The cause of the flood.
Flood is a natural phenomenon and a natural disaster, which is caused by natural factors such as rainstorm, rapid melting of ice and snow, storm surge and so on. Objectively speaking, there are irresistible reasons for frequent floods, which can be said to be "destiny".
Compared with relevant historical data, the frequency and severity of floods are quite consistent with the trend of population growth. We have to admit that the rapid population growth, the expansion of cultivated land, land reclamation around lakes, deforestation and other human activities in China constantly change the surface state, change the confluence conditions, and aggravate the degree of floods.
Rainfall depends on the sky, and water diversion depends on people. In a rainy year, whether floods cause disasters and the magnitude of flood disasters are closely related to human factors. Long-term forest destruction is an important reason.
The biggest mistake made by mankind is cutting down forests. As the main body of terrestrial ecosystem, forest has many functions, such as water conservation, soil and water conservation, climate regulation and so on, and plays an irreplaceable role in reducing flood peak. If there is a flood, there may not be a flood, but the forest is destroyed and a small flood can also cause a big flood. The flood control function of forest is mainly manifested in:
1, the canopy can intercept part of the rainstorm through its huge leaves, which can reach10 ~ 30%;
2. Its litter layer has the function of storing rainwater;
3. Because of the existence of forest, the infiltration capacity of the surface is greatly enhanced, and a large number of rapid surface runoff becomes slow underground runoff;
4. Forests can also change the surface structure of soil and enhance the ability to store precipitation;
5. The forest has huge roots, which can consolidate soil and adjust the sediment injected into rivers by floods.
The foundation of water control lies in managing mountains. Japan, with a large and dense population, put forward the slogan of "ruling the country first". The forest coverage rate in Japan is as high as 60%, which is much higher than China's 13 and 92%. However, the disposable convenient chopsticks they use are imported from China every year, and they also actively recycle them to make paper, reducing the deforestation of their own forests, which shows that the Japanese have a strong awareness of protecting forests. Both Germany and the United States have laws that require residents to apply to the government even if they cut down trees at home.
China is a developing country, and the Party and government attach great importance to afforestation and greening the motherland. When Zhou visited Xishuangbanna, Yunnan Province, he saw the phenomenon of deforestation along the hillside. He bluntly warned people that doing so would cause serious soil erosion and the consequences would be unimaginable. However, due to unreasonable logging, the forest coverage rate in the upper reaches of the Yangtze River once dropped from 30-40% in the 1950s to around 10%. At present, the forest coverage rate in Yunnan is only 24%, less than half of that at the beginning of liberation.
Secondly, another evil result of deforestation in the upper reaches of the Yangtze River is amazing soil erosion. Now it has reached 350,000 square kilometers, and the annual soil leaching amount has reached 2.5 billion tons. Sediments deposited in rivers, lakes and reservoirs reached 2 billion tons. Only one province in Sichuan flows into the tributaries of the Yangtze River in one year. If embankments with a width of 1 m are built, they can circle the equator of the earth 16 times.
Dongting Lake is the largest freshwater lake in China, which deposits more than 6,543.8+billion tons of sediment every year. Someone exclaimed: "If this continues, Dongting Lake will disappear from the earth in 50 years!" The danger of the Yangtze River lies in Jingjiang River. Because of the sediment, the riverbed of Jingjiang section is now more than ten meters higher than the ground outside the river, and it has become a veritable river on the ground except the Yellow River.
The cause and harm of flood. Self-rescue method of flood.
1. When the flood comes, people who have no time to move should quickly move to nearby hillsides, highlands, buildings, flood shelters and other places, or immediately climb on roofs, tall buildings, trees, high walls and other places for temporary refuge.
2. If the flood continues to rise, it is difficult to protect the temporary shelter, so we should make full use of the prepared life-saving equipment to escape, or quickly find some floating objects such as door panels, tables and chairs, wooden beds, large foam plastics and so on to tie them into rafts to escape.
3. If you have been surrounded by floods, try to get in touch with the flood control department of the local government as soon as possible, report your position and danger, and actively seek rescue.
Note: Never swim to escape, do not climb electrified telephone poles and iron towers, and do not climb the roof of mud houses.
If you have been involved in the flood, you must try your best to catch fixed or floating things and look for opportunities to escape.
5. When it is found that the high-voltage tower is inclined or the wire is broken and drooping, it must be avoided quickly to prevent direct electric shock or electric shock due to the "step voltage" on the ground.
6, after the flood, to do a good job of health and epidemic prevention, to prevent the spread of the epidemic.
Overview of debris flow
Debris flow is a torrent formed by saturated dilution of soft soil mountain containing sand and gravel by rainstorm and flood, and its area, volume and flow are large, while landslide is a small area of diluted earth mountain. Typical debris flow is composed of viscous mud suspended with coarse solid debris, which is rich in silt and clay.
Under the appropriate terrain conditions, a large number of water bodies soak in the solid accumulation materials in the flowing hillside or ditch bed, which reduces its stability, and the solid accumulation materials filled with water move under their own gravity, forming mudslides. Debris flow is a disastrous geological phenomenon. Usually, the debris flow erupts suddenly and violently, which can carry huge stones. Because of its high speed, high energy and strong destructive power.
The whole process of debris flow is generally only a few hours, as short as a few minutes. Debris flow is a natural disaster, which is widely distributed in some areas with special topography in the world. It is a mixed flow of soil, water and air between sediment-laden flow and landslide, which is excited by heavy rain, melting of snow and ice and other water sources in mountain valleys or hillsides.
Debris flows are mostly accompanied by floods in mountainous areas. It is different from the general flood in that the flood contains enough solid debris such as sediment and stones, the volume content of which is at least 15% and at most about 80%, so it is more destructive than the flood.
The main hazards of debris flow are destroying towns, enterprises, factories, mines and villages, causing human and animal casualties, destroying houses and other engineering facilities, and destroying crops, trees and cultivated land. In addition, mudslides sometimes block rivers, which not only hinder shipping, but also may cause floods.
The factors that affect the intensity of debris flow are debris flow, velocity and discharge, among which the flow has the most important influence on the degree of debris flow disaster. In addition, various human activities have intensified the role of these factors in many aspects and promoted the formation of mudslides.
Debris flow often occurs in canyons and areas with frequent earthquakes and volcanoes, and occurs in large quantities during heavy rains. It is a torrent of mud and stone, which erupts instantly and is the most serious natural disaster in mountainous areas.