Flow control structure
Encyclopedia
A flow control structure is a device that alters the flow of water in a stream
, drainage
channel or pipe. As a group these are passive structures since they operate without intervention under different amounts of water flow and their impact changes based on the quantity of water available. This includes weir
s, flow splitter
s and proprietary-design devices that are used for stormwater
management and in combined sewers.
Flow-control structures are known to have existed for thousands of years. Some built by the Chinese
have been in continuous use for over 2,000 years. The Chinese used these structures to divert water to irrigate fields and to actually deposit silt
in specific areas so that the channels were not blocked by silt build-up. Structures like this required yearly maintenance to remove the accumulated silt.
More modern structures add to these basic principles. In Hawaii
, there are numerous flow-control structures that have been built to irrigate the pineapple
and sugar cane fields. The purpose of these structures is to divert water into the various canals and to keep them full. When over full, they dump excess water back into either streams or other canals. Among the simplest is a low dam
across a shallow stream, forcing all of the water to one side to allow it to be easily collected in a canal. This can keep a canal full even with very low flows in a stream.
Another simple device is a series of concrete
pier
s installed in a spillway
to slow down the descending water so that it does not cause damage at the bottom of the spillway.
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
, drainage
Drainage
Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
channel or pipe. As a group these are passive structures since they operate without intervention under different amounts of water flow and their impact changes based on the quantity of water available. This includes weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...
s, flow splitter
Flow splitter
A flow splitter, in hydraulic engineering, is any device designed to break up the flow of water or nappe over a dam wall or weir. Flow splitters are used to reduce the likelihood of nappe vibration that might cause the failure of a dam wall by aerating the water flow...
s and proprietary-design devices that are used for stormwater
Stormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...
management and in combined sewers.
Flow-control structures are known to have existed for thousands of years. Some built by the Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
have been in continuous use for over 2,000 years. The Chinese used these structures to divert water to irrigate fields and to actually deposit silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
in specific areas so that the channels were not blocked by silt build-up. Structures like this required yearly maintenance to remove the accumulated silt.
More modern structures add to these basic principles. In Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, there are numerous flow-control structures that have been built to irrigate the pineapple
Pineapple
Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...
and sugar cane fields. The purpose of these structures is to divert water into the various canals and to keep them full. When over full, they dump excess water back into either streams or other canals. Among the simplest is a low dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
across a shallow stream, forcing all of the water to one side to allow it to be easily collected in a canal. This can keep a canal full even with very low flows in a stream.
Another simple device is a series of concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
pier
Pier
A pier is a raised structure, including bridge and building supports and walkways, over water, typically supported by widely spread piles or pillars...
s installed in a spillway
Spillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...
to slow down the descending water so that it does not cause damage at the bottom of the spillway.