Why do typhoons cause floods?

Why do typhoons cause floods?

A typhoon is a strong atmospheric vortex (low pressure system) generated on the tropical ocean surface. The air pressure rises violently, so there is a strong precipitation cloud system. , can bring heavy rainstorms of 100-300mm a day. After a typhoon enters the country, its winds will weaken rapidly, but the intensity of precipitation will still be maintained for a period of time. After it penetrates into the inland, it often causes floods due to long-term precipitation. When it encounters mountains, it will cause landslides, mudslides, and flash floods. Therefore, most of the casualties in typhoon disasters are caused by floods caused by its precipitation. For example, after "Bliss" entered Hunan in 2005, it brought severe floods to Chenzhou that had not been seen in a century. Why do floods occur?

Due to concentrated heavy rain or long-term rainfall in the basin, the amount of runoff flowing into the river exceeds its discharge capacity and overflows both banks or causes dam breaches, causing flooding. Why Floods

The causes of floods include human factors and natural factors.

The impact of human factors on heavy rain and flood disasters is mainly reflected in the following aspects:

(1) Destroy forest vegetation and cause soil erosion. Forests have a good water storage function. On the one hand, forests can intercept precipitation. On the other hand, forests have high soil permeability and good water storage.

(2) Constructing land around lakes affects flood storage capacity. Building embankments around lakes, enclosing rivers and lakes to create farmland, etc. will lead to a reduction in the number of lakes, sluggish rivers, and a greatly reduced flood storage capacity. Once continuous heavy rain occurs, a large amount of precipitation will flow into the river, causing the river water to surge and cause flooding. Reclamation of lakes to create farmland is the direct cause of lake shrinkage. In recent years, driven by the market economy, there has been a rise in building housing around lakes, further aggravating the decrease in lake area.

(3) Encroachment on river channels and sluggish flow of water. On the one hand, human activities continue to destroy the ecological environment, causing a large amount of sediment to flow into the river, raising the river bed and making the water flow sluggish; on the other hand, a large amount of cultivated land is encroached on, causing the area of ​​land that can absorb water to continue to shrink. Once a heavy rainstorm occurs and the river water surges, due to the impact of water-blocking buildings, the floodwater cannot drain smoothly, and it is easy to cause embankments to break and pipes to surge, causing a lot of losses.

(4) The standard of flood control facilities is low. Low. Except for the Yellow River, which has a flood control standard of once in 60 years, the embankment standards of other major rivers and lakes generally only have a return of 10 to 20 years, and the flood control standards of most cities only have a return of 20 to 30 years. Once a flood occurs that is rare in history, it will inevitably lead to a major flood.

(5) Excessive extraction of groundwater in large and medium-sized cities has caused land subsidence and aggravated urban flood risks.

Natural factors mainly include weather and climate that affect the geographical environment and terrain location:

(1) The occurrence of heavy rain is mainly affected by atmospheric circulation and weather and climate systems. a natural phenomenon. However, whether heavy rains cause disasters to social production and life depends on many factors such as social economy, population, disaster prevention and resilience, etc. Therefore, the occurrence of heavy rain disasters not only has its natural causes, but also has the influence of social and human factors. Heavy rains that can produce flood disasters are called flood-causing rainstorms, which are of greatest concern to disaster prevention and reduction departments.

(2) Weather and climate factors are the direct causes of heavy rains. When heavy rain occurs, the geographical environment becomes an important factor affecting the occurrence of disasters. The geographical environment includes terrain, landforms, geographical location, river distribution, etc. Our country has a vast area and complex terrain, including plateaus and mountains, as well as plains, basins and hills. Different terrains have different impacts on disasters caused by heavy rain. Due to their blocking effects, plateaus and mountains often form bypass currents and creeping currents, which can easily cause heavy rains. At the same time, plateaus and mountains are most likely to induce secondary disasters such as landslides and debris flows under the influence of heavy rains. Generally speaking, the ground slope in basins and intermountain plains is relatively large, and there are mostly terraces along rivers. The drainage conditions are good, and the scope of flood inundation is limited, which will not cause major disasters. However, if you encounter high-intensity and large-scale heavy rains, especially sustained heavy rains, serious disasters such as flooding and flooding of cities are likely to occur. Moreover, industry and agriculture are relatively developed in the basin and mountain plain areas, and the population is growing rapidly. The competition for land with water is becoming increasingly serious, which increases the vulnerability of these areas to heavy rain disasters. Due to its flat terrain and vast area, plain areas are less prone to impact mountain disasters, but flood-type floods are the main problem.

What caused the floods in 1998?

Large areas of precipitation and melting of snow in the upper reaches of rivers. Why do floods occur?

The Yangtze River flows through the second and third steps of my country's topography, with a large drop and rapid water flow. Jingjiang is also known as the "Jiuqu ileum". When rainbands concentrate in the Yuchang River Basin, its tributaries cannot divert floods, resulting in floods. However, after the Three Gorges of the Yangtze River were built, it played a major role in flood control.

Why did the flood occur in 1998?

Blind reclamation of lakes for farmland and occupation of flood banks in the plains are the main reasons for the rise in flood levels in the Yangtze River in recent years. From the perspective of long-term natural laws, alluvial plains of rivers are formed by the sediment carried by rivers. The economy of the Chinese nation also developed on the basis of the development of the alluvial plains of the seven major rivers. However, if development is inappropriate or overdeveloped, it will be punished by flooding. Now, we are facing this problem when developing and utilizing the land on both sides of the middle and lower reaches of the Yangtze River. Not only are the flood levels getting higher and higher, the burden of flood control is getting bigger and bigger, but the risks of flood control are also getting bigger and bigger.

The fundamental reason for the imbalance of my country’s ecosystem is that there are too many people and too little land. To rebuild the ecosystem, it must be combined with the adjustment of the economic structure, with the goal of comprehensively improving productivity, and attention should be paid to the coordination of development, reform and stability. We believe that the central government’s principles of comprehensive planning, overall consideration, addressing both symptoms and root causes, and comprehensive management are completely correct. Why do floods occur in Hainan?

First, the water is very large, and the previous flood drainage facilities are not enough, or the flood drainage pipelines are in disrepair and fail to fulfill their flood discharge tasks. Why do floods occur in Yuyao?

The direct cause is the heavy rain, the indirect cause is the typhoon, and as for the other reasons... maybe God is just a little relieved? Why does destruction of vegetation cause floods and soil collapse?

Because vegetation can conserve water and help suppress flood disasters.

The roots of plants are very developed. Because transpiration requires the evaporation of a large amount of water, the roots must penetrate into every corner of the soil to absorb water. At the same time, the roots of plants penetrate deeply into the soil. It's like a big net that fixes the soil, because when there is a flood, the water acts on the surface of the soil, and the surface of the soil is tightly held by a large number of plant roots, so the water can only wash away a small part of it. Soil does not destroy the solid structure of soil and roots. Why do floods occur?

Flood is a phenomenon in which the water contained in rivers, lakes, and seas rises above the normal water level. Floods often threaten the safety of areas along rivers, lakes, and offshore areas, and even cause submergence disasters. Floods have brought many disasters to mankind since ancient times. For example, the lower reaches of the Yellow River and Ganges River often flood, causing heavy losses. However, some river floods also bring some benefits to humans. For example, the Nile River floods regularly deposit fertile silt on the farmland in the downstream delta plain, which is beneficial to agricultural production.