Flood Prevention
A flood is an overflow of water that submerges dry land. If the water reaches land that is populated by people, such as a village, it is considered to be a natural disaster. Floods usually occur near large bodies of water, such as a lake or river. When a storm causes the water levels to rise, the water may over flow the boundaries of the river and lake and spread to areas of land that are otherwise dry.
Flood control is important because the amount of damage and loss of life can be devastating, especially in third-world countries that have limited resources. Flood control refers to the ways in which floods are prevented or the effects of floods are lessened. There are many ways in which flood control is performed and maintained, from dams to levees. Before flood control can be implemented, it must first be understood what causes a flood to occur. There are many different causes for floods and is usually a factor of the surrounding environment.
What Causes Floods?
Floods may be caused by natural characteristics of earth. This includes heavy rainfall, severe winds over large bodies of water, rapid melting of snow, high tides in coastal regions, and tsunamis. Floods may also be the result of a failure of a dam, a structure built and used to hold back the flow of water, usually to protect a living establishment, such as a village or town. Floods can usually occur near rivers regularly. The surrounding region of a part of land susceptible to floods is called the flood plain.
When severe rainstorms occur, a lot of the water is absorbed by ponds, rivers, lakes, soil, trees and other vegetation, but the water that remains is called surface runoff. When all of these entities cannot absorb all of the water, the surface runoff may cause floods to occur. Floods may occur slowly, giving plenty of advance warning to surrounding areas to lessen the effects of a natural disaster, but sometimes floods can happen with little to no warning. These are called flash floods.
Severe winds may cause floods to occur also. In coastal regions, rainfall may not be severe, but if it experiences a storm with heavy winds, those winds may carry water from the ocean or a large body of water inland. The shoreline then cannot contain the water and nearby areas are devastated by the effects of a flood.
How are Floods Contained?
Areas in the United States, such as New Orleans, are below sea level. In order to prevent floods from occurring, levees are built along the coast to prevent water from flowing into the city. The levees must be properly inspected to ensure their stability, a lesson learned after Hurricane Katrina, which damaged a large portion of the city with coastal floods.
Rivers throughout the world are carefully managed with levees, reservoirs and dams. If any of these defense mechanisms fail during a flood, sandbags are usually used to stop the flow of water. Dikes are also used, but should be used in conjunction with other methods in order to be effective.
