HR: 1340h
AN: H53B-1250    [Abstracts]
TI: Geomorphic Impacts of a Flood Control Reservoir on the Green River of Kentucky.
AU: * Kenworthy, S T
EM: stephen.kenworthy@wku.edu
AF: Dept. of Geography and Geology, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42101 United States
AB: The Green River is a tributary of the Ohio River draining approximately 24,000 km$^{2}$ in south-central and western Kentucky. Green River is also one of the most biologically diverse waterways in the United States, supporting several threatened and endangered species. Green River Lake is a flood control reservoir receiving runoff from the upper 7% (1766 km$^{2}$ of the watershed. Reduction in flood peaks since the mid-1960's have eliminated overbank inundation and floodplain sediment deposition along much of the 197 km reach below the dam. The impact of flow regulation is greatest along the tailwater reach between Green River dam and Russell Creek, the first of four major surface tributaries entering along a reach extending from 47 to 90 km below the dam. In the tailwater reach, the reduction in flood peaks and fine sediment supply has altered patterns of in-channel sediment storage and mobilization. Widespread channel bed armoring has not occurred, presumably due to continued fine sediment input from small tributaries, floodplain gullying, and bank erosion. There is little evidence of encroachment of riparian vegetation and related channel narrowing in the tailwater reach. Inputs of water and sediment from the four large, unregulated tributaries modify the impacts of the reservoir on in-channel sediment dynamics downstream of Russell Creek. During intermediate magnitude events, particularly those associated with localized storms, flow and sediment dynamics on the Green R. are likely similar to those of the pre-regulated system. However, reduction in peak flows during large storm events has decreased sediment transport capacity and thereby altered seasonal patterns of fine sediment deposition and storage. In addition, the frequency and spatial extent of streambed gravel mobilization have been reduced. River islands provide most of the remaining areas for vertical accretion of fine sediment during flow events, although the dynamics of accretion and erosion of islands and island-bar complexes are also affected by flow regulation.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1857 Reservoirs (surface)
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting