What are flash floods? Where do flash floods occur, when?

Flash floods are a type of flood that has a very fast water level when a huge amount of water moves quickly from high to low terrain.

The process of forming flash floods

Flash floods are formed when a huge amount of water is brought by thunderstorms, storms or tropical storms, or it may be because a large amount of snow and ice on the mountain melts abruptly. It can also be formed when a dam is broken or discharging a dam with a rush of mass of thousands of cubic meters per second (the amount to create flash floods depends on the width and slope of the river below. dam).

The phenomenon of flash floods is often found in places near slopes such as at the foot of mountains and hills.

Features of flash floods

Because flash floods are the phenomenon of moving a huge mass of water from high to low with increasing speed as well as greater destruction depending on the length, slope as well as the "smoothness" of the distance. it goes (places like mountains and hills without flash floods will occur frequently because there is nothing to block the water flow), it will cause extremely serious damage to the places where it passes. With high speed and high volume it can sweep away homes, trees . almost everything along the way.

The phenomenon of flash floods is often found in places near slopes such as at the foot of a hill or in the valley. Although powerful and devastating, flash floods often do not occur longer than six hours.

When the flash flood drainage path is blocked (because the dyke or large structures even if it does not clog all the flow), the mass of huge water at high speed is bounced back into a circle before it can flow as well. for rising water levels faster and more dangerous. Since the volume of water bounced back will hit the mass of water that is pouring in, causing many whirlpools to submerge everything, the whirlpools can also form under the water to draw everything around it so even when there is Life jackets that fall into this type of flood can still be submerged (this phenomenon is most visible when flash floods flood into the city or residential area close to each other) causing many difficulties for rescue.

Traveling with flash floods can have many landslides and mudslides along with the things it entails to make flash floods more dangerous as the volume moves not only with water.

Flash floods may appear on a large scale, but the wider the area of ​​flash floods, the less damage will be caused by the volume of water dispersed rather than causing damage.

Flash floods do not appear in the delta area or large rivers. Since there is no slope for running water or very little in the delta area, it can only flood the water from high to low, not anything. Also in areas with large rivers just like in the river delta will receive and regulate this amount of water, if too much, the river will overflow causing normal floods rather than forming flash floods because the water moves with speed. much slower than flash floods.

Flash floods often cause small and medium rivers, but few for large rivers.

Types of flash floods

Temporary flash floods can be divided into 3 types:

1. Floods are caused by local rain, concentrated in natural basins (almost no human impact).
2. Floods caused by heavy rains in the basins have been strongly affected by human economic activities that destabilize or disrupt basin ecological balance (change of cover, flow regime, amount of storage) or basin characteristics .
3. Floods caused by the sudden dismantling, breaking of a volume of accumulated water due to breakage of dams or dams to hold water, ice dams .

Harm of flash floods

Flash floods often cause small and medium rivers, but few for large rivers. Survey results of basins have caused flash floods to show that flash floods have appeared again every 30 years. However, there are many places where flash floods have occurred consecutively because of these strongly degraded basins. Flash flood is a complex, diverse and deeply local problem.

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