http://www.answers.com/topic/river-engineering

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Note added at 24 mins (2009-08-11 14:41:06 GMT)
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River engineering is the process of planned human intervention in the course, characteristics or flow of a river with the intention of producing some defined benefit. People have intervened in the natural course and behaviour of rivers since before recorded history - to manage the water resources, to protect against flooding or to make passage along or across rivers easier. From Roman times, rivers have been used as a source of hydropower. From the late 20th century, river engineering has had environmental concerns broader than immediate human benefit and some river engineering projects have been concerned exclusively with the restoration or protection of natural characteristics and habitats.

In the United States river engineering is often called hydromodification, a term which also includes alterations to non-riverine water bodies such as coastal waters (estuaries and bays) and lakes. The U.S. Environmental Protection Agency (EPA) has defined hydromodification as the "alteration of the hydrologic characteristics of coastal and non-coastal waters, which in turn could cause degradation of water resources."[1]

Before undertaking any river engineering, it is most important that the physical characteristics of the river is investigated, for these vary greatly in different rivers, being dependent upon the general configuration of the land, the nature of the surface strata and the climate of the country which the rivers traverse. Legislation in many countries, including in Europe and the U.S., also requires an environmental impact assessment.