The ecological basis of river restoration: 2. Defining restoration from an ecological perspective

The main effects of regulation, channelisation, and diversion works on river ecosystems are a decrease in habitat diversity, and a shift from native to exotic biodiversity. To restore a river is to attempt to bring it back to high levels of ecological integrity - conditions as close as possible to those that unimpaired rivers would have had in the region, taking into account the prevailing socioeconomic, political, and technological constraints. When a river is highly managed, this goal is unrealistic, the objective should then be ecological health - that the river ecosystem provides services to society in a sustainable fashion, without degradation for future use, performing all of its functions properly, with minimal outside care. If the natural flow and water quality régimes are restored, and the channel is reconnected to its floodplain, a river left to itself will regain a high ecological integrity, without need for further intervention. © 1998 American Society of Civil Engineers