Amazon River Dolphin

• Levees, known as dikes in Europe, may be built to prevent river water from flowing on floodplains or floodways.
• Canals connect rivers to one another for water transfer or navigation.
• River courses may be modified to improve navigation, or straightened to increase the flow rate.
River management is a continuous activity as rivers tend to 'undo' the modifications made by people. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or catastrophic failure. The benefits sought through managing rivers may often be offset by the social and economic costs of mitigating the bad effects of such management. As an example, in parts of the developed world, rivers have been confined within channels to free up flat flood-plain land for development. Floods can inundate such development at high financial cost and often with loss of life.