HR: 08:15h
AN: H41A-02    [PDF]
TI: Erosion and Sedimentation in Response to Climate Change: a Numerical Study Using a Multiple Grain-size Sediment Transport Model
AU: * Gasparini, N M
EM: nicoleg@alum.mit.edu
AF: MIT, Department of Civil and Environmental Engineering, Cambridge, MA 02139 United States
AU: Bras, R L
EM: rlbras@mit.edu
AF: MIT, Department of Civil and Environmental Engineering, Cambridge, MA 02139 United States
AU: Tucker, G E
EM: greg.tucker@geog.ox.ac.uk
AF: Oxford University, School of Geography and the Environment Mansfield Road, Oxford, OX13TB United Kingdom
AB: This study investigates changes in the surface texture and slope of fluvial channels in response to an increase in fluvial discharge. We use a two grain-size (sand and gravel) sediment-transport model to calculate changes in surface texture through time. Initially, erosion of both grain sizes increases in the head waters, and a large flux of sediment is sent downstream. Below the areas of incision, gravel is deposited, while further downstream sand is deposited as well. During this period, network concavity is reduced. Eventually, the entire network begins to erode at a faster rate than the equilibrium rate (the rate of base-level lowering) and slopes throughout the drainage network become shallower than they would be at equilibrium. Even on the shallower slopes, erosion rates remain high because a large amount of gravel is eroded out of the channel and the surface remains fine. At later times, the channel surface coarsens and the channel slope increases again. All of these changes - decreasing and increasing slopes and coarsening and fining of the channel surface - result from a single increase in runoff across the landscape. The initial response in the network differs from the response at later times. The model predictions illustrate that there may not be a one-to-one relationship between climate change and the texture of alluvial deposits or transient channel slopes.
DE: 1800 HYDROLOGY
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1848 Networks
SC: Hydrology [H]
MN: 2003 Fall Meeting