Author
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GORE JAMES A - THE CONSERVANCY |
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SHIELDS F D JR - 6408-05-15 |
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Submitted to: Bioscience
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/1/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Large river ecosystems are among the world's greatest biological resources. Development of rivers and their floodplains has severely damaged these systems, and most damage has occurred relatively recently (over the 100 to 200 years). Although restoration of rivers to a pristine state is incompatible with current human population levels, considerable progress has been made in generating techniques for partial restoration, also termed rehabilitation. These techniques have been identified from a review of the scientific literature, digested and evaluated. Habitat rehabilitation techniques include planting woody vegetation on banks, restoring meandering channel alignments, constructing low dams (weirs), and building spurs and artificial riffles out of stone. Dredging floodplain lakes, sloughs, and other types of backwaters has been widely practiced, as has diversion of sediment-laden floodwaters away from these areas. When habitats are rehabilitated, biological recovery usually follows rapidly (within months). This information should facilitate selection of the most effective rehabiltation techniques by river managers and design of research projects to fill knowledge gaps by scientists studying large river restoration Technical Abstract: Even though the major rivers of the world display considerable individuality, human impacts on their physical characteristics are quite similar from river to river. In general, developed rivers have undergone comprehensive planform stabilization, gradual loss of low-velocity and backwater habitats, loss of in-channel physical heterogeneity, and uncoupling of river and floodplain ecosystems. Restoration of large rivers to a pristine or virgin state is incompatible with present human population levels. Instead, rehabilitation of developed river systems, meaning the restoration of some of their ecological functions and values, is a more logical goal. Large river rehabilitation techniques include manipulations of the channel, backwater area treatments, interventions in the riparian zone and floodplain, and flow regulation. River channel manipulations include substrate replacement (e.g., riffle construction), development of cover, and actions intended to restore hydraulic conditions (weir placement, meander restoration). Backwater treatments center around control of sediments by dredging or diversion structures, while flow regulation by dams and diversions restores duration and timing of floods, at least on a limited scale. Recovery of insect and fish populations in restored riverine habitats is governed by disturbance scale, size and location of colonization source, and the type of colonists. Proposals and concepts for large river restoration are much more abundant than demonstrations. |
