Artificial whitewater

An artificial whitewater course (AWWC) is a site for whitewater canoeing, whitewater kayaking, whitewater racing, whitewater rafting, playboating and slalom canoeing with artificially generated rapids.
Course types.
Main types of course:
Flow diversion.
These work by diverting a natural river through boulder placement or damming, or by creating new channels next to an existing river, possibly by a weir or power station outflow.
Tidal action.
Created in estuaries with large tidal reaches, on a barrage across the river. The barrage is opened during a rising high tide to allow the sea water in, then shut as the tide turns. The water stored above the barrage is then forced through an artificial channel to provide water features.
Pumped.
The nature of artificial whitewater courses necessitates the need for a drop in the river, and enough water flow to provide hydraulics. When this isn't possible (often in flat low-lying areas), electric pumps are used to lift and re-circulate the water to the top of the course. The shapes of these courses are commonly circular or U-shaped.
Pumped courses are extremely expensive to run, typically 1-2 megawatts of electrical power are needed to pump 15 cubic metres per second of water down a course with a 5-meter drop in height.
Altered Riverbed.
These courses are created in existing natural river channels, but are enhanced with strategic placement of new rocks, boulders, or concrete structures. Some are downstream of river or channel wide dams and therefore have some level of flow optimization, others are subject to seasonal flows. 