What are the main natural disasters?

Tornado is the strongest vortex phenomenon in the atmosphere, which often occurs in thunderstorm weather in summer, especially in the afternoon and evening. Although the scope of influence is small, it is extremely destructive.

Tornadoes often pull up trees, overturn vehicles, destroy buildings and so on. They often destroy crops and tens of thousands of fruit trees instantly, interrupt traffic, collapse houses, and cause human and animal lives and economic losses.

2. Tsunami

Tsunami is a destructive wave caused by submarine earthquake, volcanic eruption, submarine landslide or meteorological change. The wave speed of tsunami is as high as 700 ~ 800 kilometers per hour, and it can cross the ocean in a few hours. Wavelength can reach hundreds of kilometers, can spread thousands of kilometers, and energy loss is small; In the vast ocean, the wave height is less than one meter, but in the shallow sea coast, the wavelength becomes shorter and the wave height increases sharply, reaching tens of meters, forming a "water wall" with great energy.

Tsunami is mainly controlled by seabed topography, coastline geometry and wave characteristics. Roaring waves and ice walls repeat every few minutes or dozens of minutes, destroying banks, flooding land, taking away lives and property, which is extremely destructive. The global tsunami occurrence area is roughly consistent with the earthquake zone. There are about 260 recorded destructive tsunamis in the world, averaging about once every six or seven years.

Earthquakes and tsunamis around the Pacific Ocean account for about 80%. The earthquakes in the Japanese archipelago and its adjacent waters account for about 60% of the Pacific earthquakes and tsunamis, and Japan is the country suffering from the most severe earthquakes and tsunamis in the world.

3. Storm surge

Storm surge is a catastrophic natural phenomenon. Due to severe atmospheric disturbances, such as strong winds and sudden changes in air pressure (usually referring to disastrous weather systems such as typhoons and extratropical cyclones), when the sea water rises and falls abnormally and overlaps with astronomical tides (usually referring to tides), if this superposition happens to be the superposition of high surges formed by strong and low-pressure storm surges and astronomical climaxes, it will form stronger destructive power. It can also be called "storm increasing water", "storm tsunami", "meteorological tsunami" or "tidal wave".

Step 4 flash floods

Mountain torrents refer to the skyrocketing floods in mountain streams and gullies. Sudden mountain torrents, concentrated water flow, strong scouring destructive power. Sediment and even stones are entrained in the water flow, which often causes local floods, which are generally divided into rainstorm flash floods, snowmelt flash floods and glacier flash floods. By raising flood control standards, adjusting human activities, and enhancing people's awareness of disaster prevention and avoidance in mountainous areas, the purpose of reducing the frequency of mountain torrents or reducing their harm can be achieved.

In the planning of mountain torrents prevention and control, engineering measures should be combined with non-engineering measures in the near future, and plant measures should be taken in the long term. On June 27th, 2006, 10, the State Council officially approved the National Mountain Torrential Disaster Prevention and Control Planning Report. This is the first special plan for the prevention and control of mountain torrents in China, which was jointly organized by the State Council.

5. Debris flow

Debris flow refers to a special torrent containing a lot of sediment and stones caused by heavy rain, blizzard or other natural disasters in mountainous areas or other areas with deep valleys and steep terrain. Debris flow has the characteristics of strong suddenness, fast velocity, large flow, large material capacity and strong destructive power. Debris flow often destroys roads, railways and other transportation facilities and even villages and towns, causing huge losses.