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1 ? Figure 8. Landsat image of the study reach in the Oconee River near Milledgeville, Georgia. The red area around the river is floodplain bottom- land hardwood swamp. The river is approximately 100 in wide. Understanding, through research and modeling, the ecological pro- cesses that are altered by distur- bance and the ways that a species or group of species would be affected or react, much less a whole ecosys- tem, is an enormous undertaking, even when the basic biology is known. When the basic background biology and ecology are unknown, traditional biological research may not provide sufficient information in the time frame necessary for the conservation of a stream's biota. In contrast, there may often be cases where an assessment of the geomorphic consequences of a dam can be accomplished quickly. Pre- serving the physical habitat of a stream is likely to be a major step toward conserving its biota. How- ever, knowing that something .: :. '. 'A"te""„.... . .. • a Figure 9. The Rakaia River is a typical undammed New Zealand South Island braided river (view facing downstream). geomorphically undesirable is likely to happen as a result of a dam does not mean that it will be possible to propose anything, short of not build- ing the dam, to prevent it from hap- pening. Further research into how dam design, siting, and operation can ameliorate ecologically delete- rious geomorphic changes will even- tually reveal how often we will be able both to identify and to avoid significant alterations of river eco- systems. Acknowledgments The article has benefited signifi- cantly from suggestions by Chris- tine Champe, Holly Earl, Angela Percival, Mary Power, George Read, and two anonymous reviewers. References cited Bain, M. B., and J. M. Boltz. 1989. Impor- tance of floodplain wetlands to riverine fish diversity and production: study plan and hypothesis. Report prepared by Ala- bama Cooperative Fish and Wildlife Re- search Unit for National Ecology Re- search Center, US Fish and Wildlife Service, Auburn University, AL. California Department of Water Resources (CDWR). 1992. Project report: Sacra- mento River spawning gravel restoration phase I. Office report. CDWR, Northern District, Red Bluff, CA. Cummins, K. W. 1992. Catchment characteris- tics and river ecosystems. Pages 125-135 in March 1995 191 Figure 10. Heavily vegetated bars on the Waitaki River (view facing upstream). Vegetation, which has proliferated since the construction of a dam upstream, has stabilized the locations of existing channels.