Downstream Geomorphic Impacts of Large Dams on American Rivers

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Arizona State University The objective of this investigation is to examine the downstream impacts of large dams on the nation's rivers. In particular the PI wishes to develop new knowledge about how dam installation and operation have affected the characteristics of river channels and riparian environments. Specific questions include the temporal and spatial distributions of stream power downstream in relation to scale and engineering characteristics of dams, as well as, operating rules. In addition the geographic effects of distributions of stream power will be assessed from the perspectives of channel width, flood plain dimensions, channel patterns and near channel landforms, and spatial distributions of riparian ecosystems. The strategy is to compare present conditions on experimental river reaches that have been impacted by dams with nearby similar control reaches that are without such structures for up to 42 of the largest dams in the country. Methods of investigation focus on hydrologic analyses of streamflow data using statistical techniques, geographic analyses of aerial photographic images using GIS, and field investigations to collect sediment and vegetation data. The project will advance present fluvial theory for impounded rivers for such theory is in its infancy and does not include generalizations about the range of hydrologic and geomorphic impacts of dams. From an applied perspective the work will provide new information on the effect of rivers on critical habitat.