Flood

Flood

A flood is an overflow of an expanse of water that submerges land, a deluge. 

In the sense of "flowing water", the word is applied to the inflow of the tide, as opposed to the outflow or "ebb". It is usually due to the volume of water within a body of water, such as a river or lake, exceeding the total capacity of the body, and as a result some of the water flows or sits outside of the normal perimeter of the body. 

It can also occur in rivers, when the strength of the river is so high it flows right out of the river channel, usually at corners or meanders. These of course, are not applicable in such instances as sea flooding. A flood occurs when an area of land, usually low-lying, is covered with water. The worst floods usually occur when a river overflows its banks. Floods happen when soil and vegetation cannot absorb all the water. 

The water then runs off the land in quantities that cannot be carried in stream channels or kept in natural ponds or man-made reservoirs. Periodic floods occur naturally on many rivers, forming an area known as the flood plain. 

These river floods usually result from heavy rain, sometimes combined with melting snow, which causes the rivers to overflow their banks. A flood that rises and falls rapidly with little or no advance warning is called a flash flood. Flash floods usually result from intense rainfall over a relatively small area, as happened in 2007 with the Sudan floods. 

Coastal areas are occasionally flooded by high tides caused by severe winds on ocean surfaces, or by tsunami waves caused by undersea earthquakes.