What is the concept of a flood, how large an area, or how many cubic meters or more

Hehe, the flood is different for different rivers. The general concept is that when a river overflows its levees, it becomes a flood. There are also floods that exceed the warning level of the river.

All I know is ...

One. Flood Definition:

It is the phenomenon that rivers, lakes, oceans and other places, the water body suddenly increases in a relatively short period of time, resulting in the water level **, and the phenomenon of inundating places that are usually not in the water, often threatening the safety of relevant places or leading to inundation disasters.

Two. Types of Floods:

1. According to the different areas where floods occur, they can be divided into river floods, lake floods, coastal floods, mountain floods, etc.

2. According to different causes, floods can be divided into:

1) Torrential flood: It is a flood formed by rainfall.

2) Snow melt (ice) flood and rain and snow mixed flood: that is, if there is alpine snow or icy areas in the river basin area, when the temperature rises sharply, the snow (ice) melts rapidly, and the snow (ice) flood will be formed. If there is rain at the same time, a mixed flood of rain and snow will be formed.

3) Ice flood: Ice flood, also known as Ling Xun, is a flood formed by the freezing of the river when the temperature drops and the ice blocking the river channel when the temperature rises and the temperature rises, which is the result of the comprehensive action of heat, power, river topography and other factors.

4) Flash floods and debris flows: flash floods are localized floods formed by sudden rainstorms in mountain valleys or the melting of a large amount of snow (ice) due to a sharp rise in temperature; Debris flow is a localized flood caused by heavy rain or a large amount of melting ice and snow in mountainous areas where the surface geology is loose, the slope and bank wall are prone to collapse and there is a lot of sediment.

5) Dam failure flood: refers to the flood caused by the sudden collapse of the dam or other water-retaining structures and the sudden discharge of a large amount of impounded water.

6) Astronomical tide: It is the phenomenon of increasing and decreasing water in the oceans on the earth due to the tidal attraction of the moon and the sun.

7) Storm surge: It is a phenomenon caused by the rapid change of meteorological factors such as air pressure and strong wind, which causes the abnormal rise and fall of the water level of the coast and estuary.

Flooding is a phenomenon caused by natural factors such as heavy rainfall, rapid melting of ice and snow, storm surge, etc., the rapid increase in the amount of sea water in rivers and lakes or the rapid flow of water levels.

When heavy rain or snowmelt occurs in the basin and produces runoff, it will converge at the outlet section of the river according to its distance. When the runoff in the vicinity arrives, the flow of the river begins to increase and the water level is corresponding**, which is called a flood rise. When most of the high-intensity surface runoff converges in the outlet section, the river flow increases to the maximum value called the peak flood flow, and the corresponding maximum water level is called the peak flood level.

At a certain time after the rainstorm stops, the river flow and water level return to the original state when the surface runoff and the amount of water stored in the ground, topsoil and river network have flowed out of the outlet section. The curve connecting the whole process of the flood from the rise to the peak to the fall is called the flood process line, and the total amount of water flowing out is called the total flood volume.

Disaster process. China is a flood-prone country, which causes a large number of property losses and human resources every year, so it is of great theoretical and practical significance to study the risk factors of regional floods. The formation process of regional flood includes flood risk factors, flood risk space, and flood risk bearers.

A larger flood is a flood with a return period of 10 to 20 years. In hydrology, in addition to using flood frequency to measure the size of floods, it is also commonly used to express the return period (in years), which refers to the average number of years when a flood of a certain magnitude occurs over a long period of time. Floods with a return period of 10 to 20 years are considered "major floods".

Rivers, oceans, lakes and other water bodies ** exceed a certain water level, threatening the safety of the relevant areas, and even causing disasters to the flow of water. Also known as the Great Water. The word flood comes from the pre-Qin "Shangshu Yaodian" in China.

Since then, there have been many recorded floods over the past 4,000 years, and the earliest record of a flood in Europe dates back to 1450 BC. The Tigris Euphrates River in Western Asia and the Nile River in Africa date back to the 40th century BC.

CompareThe Great FloodIt refers to a flood that occurs once in 10-20 years during the return period of peak flood flow or flood volume.

Emergency plan. Floods are classified: a general flood is a flood that occurs once in 10 years with a return period of 5 to 10 years for peak flood flow or flood volume.

The larger flood is a flood that occurs once in 10 to 20 years. The Great Flood is a flood that occurs once in 20 50 years. A catastrophic flood is a flood that occurs more than once in 50 years.

What needs to be explained: the concept of a flood that occurs once in 5 years, 10 years, 20 years, 50 years, 100 years. At present, mathematical statistics are generally used to describe the "likelihood" of a flood of a certain size.

For example, "once in 50 years" is such a description. "Once in 50 years" can be understood as the "recurrence of floods every 50 years", but it should be clear that this "every 50 years" is not in the exact sense, but in the statistical sense.

Floods of this size may occur frequently for several years or not once in 100 years, but according to the historical period of the river's existence (from the appearance of the river to its demise), the flood of this size occurs on average "once every 50 years".

Flood self-rescue

1. When the flood comes, those who have not had time to move should quickly move to the nearest hillside, high ground, building, flood shelter and other places, or immediately climb to the roof, high-rise buildings, big trees, high walls and other high places to take shelter.

2. If the flood continues, and the temporary shelter is difficult to protect itself, you should make full use of the prepared life-saving equipment to escape, or quickly find some door panels, tables and chairs, wooden beds, and large pieces of styrofoam.

Wait for the floating material to form a raft to escape.

A larger flood is a flood that occurs once in 10-20 years.

According to the level of water and the degree of threat to the safety of the embankment, the flood and water level are generally divided into general flood, large flood, major flood, extraordinarily large flood and warning water level and guarantee water level according to the grade.

The return period of the peak flow or volume of the general flood is a flood that occurs once in 10 years.

The return period of the peak flow or flood volume of a larger flood is a flood that occurs once in 10 or 20 years.

The return period of the peak flow or volume of a major flood is a flood that occurs once in 20 to 50 years.

The return period of the peak flow or volume of a catastrophic flood is greater than that of a flood that occurs once in 50 years.

RepresentationIn hydrology, in addition to using flood frequency to measure the size of floods, it is also commonly used to express the return period (in years), which refers to the concept of how many years a flood of a certain magnitude occurs on average over a long period of time.

For example, the return period of a flood of a certain magnitude is 100 years (commonly known as a 100-year flood), which refers to the possibility that a flood of this magnitude will occur once every 100 years on average over a long period of time, but it cannot be understood as occurring once every 100 years. The reality is that such floods may occur more than once in 100 years, or not once.