What is a flood? | What are the types of floods and their causes? | What is a flash flood? | What kinds of damage of floods responsible for? | How can floods be controlled?

  What is a flood?   [Top]

  A flood is a large amount of water that covers what is normally dry land. They can be caused by heavy rainfal or snowmelt in a short period of time. They can also be caused by the overflowing of rivers, seas, or lakes onto land.

  What are the types of floods and their causes?   [Top]

  Most floods are river-based floods associated with the surface run-off. There are two main types of surface run-off floods:

• Flash floods: These floods are associated with a short period of intense rainfall, usually falling onto a small river, which causes an rapid increase in the flow of the stream.
  
• Widespread river floods: These floods have a greater area involved than flash floods, usually taking longer to develop, involving a major area and larger rivers.
  

The third possible type is the storm surge associated with hurricanes.

  What is a flash flood?   [Top]

  Flash floods occur when large amounts of rain cause a river or other body of water to suddenly overflow. These types of floods usually occur near mountains and cause a lot of damage. Flash floods are possible whenever there is an intense onto a small area. A downpour alone will most likely not cause a flood unless other factors are involved. These factors can be described as anything that inhibits saturation of the ground and causes surface run-off, for example, steep slopes. Flash floods are associated more with mountains than with coastal plains. Thins soil and sparse vegetation of the mountains may be directly associated with the slopes. It is possible for flash floods to occur in the mountains (in winter or early spring) by having water fall on frozen soil rather than saturated soil. The may also be a result of human manipulation of the land's surface. Certain factors, such as the soil moisture content before a storm, are more meteorologically oriented. Probably the best known cause of flash floods are convective storms. Convective storms are perfect rainfall sources, but even then it is common to need saturated soil before a flood can occur. Spring is the common time for flash floods to occur (after the onset of convective storms, but before high evaporation rates are established).

  What kinds of damage are floods responsible for?   [Top]

  Floods destroy property and strip topsoil away from land, leaving it barren. Floods are also responsible for the greatest loss of life than any other natural disaster. Floods, unlike the rest of the natural disasters, can be helpful. For example, the flooding of the Nile River in Egypt fertilizes the land by bringing nutrients to the soil.

  How can floods be controlled?   [Top]

  Floods cannot be prevented, but they can be controlled. Flood waters can be dammed and channeled. Dams allow water to be stored, and channels allow water to be quickly drained into the sea. A flood is, for the most part, the result of a single meteorological event that is short-lived. Usually, only a small, well defined area is involved. The major concern with floods is forecasting of the timing, location, and amount of rainfall. This way, accurate and timely warnings can be issued.