Презентация "Природные катастрофы - наводнения"

FLOOD

is an overflow of water that

submerges land which is usually dry .

Floods may occur as an overflow of

water from water bodies, such as a

river or lake, in which the water

overtops or breaks levees or it may

occur in rivers when the flow rate

exceeds the capacity of the river

channel. Some floods develop slowly,

while others can develop in just a few

minutes. Floods can be local, impacting

a neighborhood, or very large,

affecting entire river basins.

Floods can happen on flat or low-lying areas when the ground is saturated and water cannot run off quickly

enough. Catastrophic flooding is usually

associated with major infrastructure

failures as the collapse of a dam, but

they may also be caused by damage

sustained in an earthquake or volcanic

corruption.

The most prominent floods

Flood in Saint Petersburg, 1824

421 cm above normal, 300 thousand injured

The most prominent floods

China floods, 1931

were the series of floods that occurred

in Nanjing, capital of the Republic of

China with about 2,5 million injured.

The most prominent floods

The Great Mississippi flood, 1927

was the most destructive river flood

in the history of the United States. About 130 000 houses were destroyed and 246 people drowned.

In many countries around the world,

waterways prone to floods are often

carefully managed. Defenses such as

levees and weirs are used to prevent

waterways from overflowing their

banks. Flood controls such, as dams,

can be built to reduce the occurrence

of floods.

Floods can also bring many benefits,

such as recharging ground water. Flood

waters provide much needed water

resources in arid regions. Also some

fishes make use of floods in order to

reach new habitats.

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