HR: 1340h
AN: H53B-1251    [Abstracts]
TI: Multi-scale Analysis of Sediment Yield in a Glaciated Environment
AU: * Wemple, B C
EM: bwemple@uvm.edu
AF: Dept. of Geography University of Vermont, 94 University Place 202 Old Mill, Burlington, VT 05405 United States
AU: Ambers, R K
EM: rambers@sbc.edu
AF: Dept. of Environmental Studies, Sweet Briar College, Sweet Briar, VA 24595 United States
AB: Global measurements of sediment yield in watersheds of different sizes have produced a general pattern. All other things being equal, large watersheds tend to have a smaller yield than small watersheds because there are more opportunities for sediment storage within a larger system. In the Little River valley near Stowe, VT, the influence of glacial geology and land use counteracts this trend. Some small watersheds, such as that of Ranch Brook (10 km2), West Branch (10 km2), and Stevenson Brook (15 km2), minor tributaries of the river, have sediment yields ranging from 5-30 tons/km2/year. In contrast, sediment yields measured through surveys of the Waterbury Reservoir (282 km2 watershed) on the Little River and the much smaller east branch of the reservoir (17 km2 watershed) have a yield of 200-220 tons/km2/year. (These numbers do not take reservoir trap efficiency into account and thus are minimum values.) The underlying causes of this bimodal distribution in sediment yield are the glacial history of the area and modern land use. During the Pleistocene, glaciers scoured away much of the regolith on the hillsides, leaving small modern streams with relatively little transportable sediment available. Thick deposits of glacial outwash were left in the valleys, so larger modern rivers such as the Little River, flow through poorly consolidated, highly erodible materials. Agriculture and development in the larger, relatively low-gradient valleys contribute to sediment production. The large sediment supply overwhelms the increased storage available in lower gradient areas and results in a substantially higher sediment yield compared to small, mountain streams in the area.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1827 Glaciology (1863)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting