HR: 10:20h
AN: C52A-01    [Abstracts]
TI: Do Glacier Dams Retard River Incision Into Southeast Tibet?
AU: * Korup, O
EM: korup@slf.ch
AF: Swiss Federal Research Institutes WSL/SLF, Flueelastr. 11, Davos, 7260, Switzerland
AU: Montgomery, D R
EM: dave@ess.washington.edu
AF: Quaternary Research Center, Department of Earth and Space Sciences, University of Washington, WA, Seattle, 98195-1310, United States
AB: The southeastern fringe of the Tibetan plateau around the Namche Barwa syntaxis is characterized by rapid uplift and fluvial incision, having created spectacular relief along the Yarlung Tsangpo river gorge. This region hosts numerous monsoonal temperate glaciers, some of which have been historically dynamic, and many of which have advanced from steep tributaries to repeatedly block or divert trunk rivers during the Quaternary. We propose that repeated glacial damming has resulted in knickpoint formation, as well as valley-floor aggradation and increases in active channel widths that serve to retard fluvial bedrock incision into the flanks of the Tibetan Plateau. The coupled reduction of fluvial incision upstream of glacier dams and enhanced incision downstream of the lowermost dams would act to maintain an edge to the Tibetan Plateau by defeating propagation of knickpoints into the Plateau in a region of high uplift and precipitation. The positions of several large moraine dams in an area where local relief and erosion are highest require depressions of the regional equilibrium line altitude (ELA) of ~ 450 m, which is within the range of ELA depression for Holocene glacial advances. Such an ELA depression would on average impound ~ 40% of the river network of major rivers upstream of glacier dams; estimated, though debated, Last Glacial Maximum ELA depression of 1000 m would result in damming of about 75% of these river networks. Whether driven by increased monsoon precipitation, temperature fluctuations, or changes to supraglacial sediment flux, Quaternary glacier advances indirectly contribute to effectively retarding river incision into southeast Tibet.
DE: 0720 Glaciers
DE: 1808 Dams
DE: 1825 Geomorphology: fluvial (1625)
DE: 1856 River channels (0483, 0744)
DE: 1862 Sediment transport (4558)
SC: Cryosphere [C]
MN: 2007 Fall Meeting