Flood control channels are large and empty basins which let water flow in and out (except during

flood A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...

ing) or dry channels that run below the street levels of some larger

cities A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...

, so that if and when a flood occurs, the water will run into these channels, and eventually drain into a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

or other body of

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

. Flood channels are sometimes built on the former courses of waterways as a way to reduce flooding.

Levees

Flood control channels are not to be confused with watercourses which are simply confined between levees. These structures may be made entirely of

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

, with concrete sides and an exposed bottom, with

riprap Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. ...

sides and an exposed bottom, or completely unlined. They often contain grade control sills or

weir A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of l ...

s to prevent

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

and maintain a level streambed.

Distribution

By definition, flood control channels range from the size of a street gutter to a few hundred or even a few thousand feet wide in some rare cases. Flood control channels are found in most heavily developed areas in the world. One city with many of these channels is

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...

, as they became mandatory with the passage of the Flood Control Act of 1941 passed in the wake of the

Los Angeles Flood of 1938 The Los Angeles flood of 1938 was one of the largest floods in the history of Los Angeles, Orange, and Riverside Counties in southern California. The flood was caused by two Pacific storms that swept across the Los Angeles Basin in February-Ma ...

External links

LA River Flood Control Channel
Flood control Environmental engineering Rivers {{engineering-stub

Levees

Distribution

See also

External links