Timescales of stream bed stabilization due to altered flow and sediment regimes below dams

HR: 1340h
AN: H53B-0457 [Abstracts]
TI: Timescales of stream bed stabilization due to altered flow and sediment regimes below dams
AU: Salant, N
EM: nira@alum.dartmouth.org
AF: Dartmouth College: Earth Sciences, HB 6105 Earth Sciences Department Dartmouth College, Hanover, NH 03755 United States
AU: Renshaw, C
EM: renshaw@dartmouth.edu
AF: Dartmouth College: Earth Sciences, HB 6105 Earth Sciences Department Dartmouth College, Hanover, NH 03755 United States
AU: * Magilligan, F
EM: fjm@dartmouth.edu
AF: Dartmouth College: Geography, HB 6017 Geography Department Dartmouth College, Hanover, NH 03755 United States
AB: Altered flow and sediment transport regimes due to impoundment can result in significant channel bed composition changes which exacerbate the geomorphic and ecological effects of flow regulation. Using long-term discharge and cross-sectional data in combination with a two-fraction sediment transport model, we assess changes in the downstream bed of two flow-regulated rivers with equivalent dam-induced changes in flow but opposite changes in sediment flux. Supply limitation has led to incision and armoring in one case while supply excess has led to aggradation and embeddedness in the other. Under limited sediment supply, bed elevation variability decreases soon after impoundment, while excess sediment supply results in a decades-long gradual decrease in both bed elevation variability and depth of incision. Although the balance of sediment supply and transport differs between dam managements styles, both the immediate and more gradual changes can be explained within the framework of a two-fraction sediment transport model. Our results demonstrate the importance of considering bed composition on sediment transport predictions and the development of management strategies for ecosystem maintenance.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1856 River channels (0483, 0744)
DE: 1861 Sedimentation (4863)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: Fall Meeting 2005