HR: 0800h
AN: H21A-0194    [Abstracts]
TI: Characterization of sediment sources in the Le Sueur River watershed, southern Minnesota
AU: * Belmont, P
EM: belmont@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455, United States
AU: Perg, L
EM: lperg@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455, United States
AU: Day, S
EM: dayxx196@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455, United States
AU: Jennings, C
EM: carrie@umn.edu
AF: University of Minnesota, Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455, United States
AU: Gran, K
EM: kgran@d.umn.edu
AF: University of Minnesota Duluth Department of Geological Sciences, 229 Heller Hall 1114 Kirby Drive, Duluth, MN 55812, United States
AU: Johnson, A
EM: joh04308@d.umn.edu
AF: University of Minnesota Duluth Department of Geological Sciences, 229 Heller Hall 1114 Kirby Drive, Duluth, MN 55812, United States
AU: Wilcock, P
EM: wilcock@jhu.edu
AF: Johns Hopkins University Department of Geography and Environmental Engineering, 3400 North Charles Street, Baltimore, MD 21218, United States
AB: Low-relief, tectonically quiescent landscapes are fundamentally important for fulfilling economic and societal needs. In historic times humans have, no doubt, greatly enhanced sediment yield from these landscapes to an extent that is comparable to, if not greater than that from many tectonically active areas, yet they have received little attention from the geomorphic community. Currently, our understanding of integrated watershed sediment dynamics in low-relief landscapes is insufficient for proper development of widely-applicable, predictive models of sediment sources, transport and storage. This insufficiency limits our ability to deconvolve anthropogenic versus natural drivers of landscape change and limits our ability to develop reasonable management goals in these economically important landscapes. The Le Sueur River, southern Minnesota, is impaired by sediment under the Clean Water Act and is one of the largest contributors of sediment and colloidal phosphorus to the Minnesota River. The goal of this project is to develop an integrated sediment budget for the Le Sueur watershed that can be used to inform best management practices to achieve the greatest reduction of in-stream turbidity. We are combining field mapping and granulometry with geomorphic modeling, LiDAR technology, and strategic cosmogenic nuclide analysis to determine the proportion of the suspended load that is coming from erosion of uplands, streambanks, bluffs, and ravines, respectively. Preliminary analysis of the relationship between local channel slope and contributing drainage area indicates two distint knickzones migrating up the Le Sueur River system. A graded reach (river km 35-80) is bound on either side by the two knickzones. Our experimental design will test two competing hypotheses. If erosional hotspots are linked to knick migration, we hypothesize that most proximate to the lower extent of the knicks: a) ravines will be steeper and contain convex banks and b) erosion rates from ravines and tributaries will be highest. If, on the other hand, the erosional system is being driven by a distributed, watershed-scale process, such as land use or climate change, we expect that ravine morphology will be consistent and erosion rates will be elevated throughout the basin.
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1871 Surface water quality
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting