HR: 0800h
AN: H41D-0761    [Abstracts]
TI: Modeling Fluvial Incision and Transient Landscape Evolution: Influence of Dynamic Channel Adjustment
AU: * Attal, M
EM: mikael.attal@ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW, United Kingdom
AU: Tucker, G E
EM: gtucker@cires.colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences, and Dept. of Geological Sciences, University of Colorado, Boulder, CO 80309, United States
AU: Cowie, P A
EM: patience.cowie@ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW, United Kingdom
AU: Whittaker, A C
EM: alex.whittaker@glg.ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW, United Kingdom
AU: Roberts, G P
EM: Gerald.Roberts@ucl.ac.uk
AF: Research School of Geological and Geophysical Sciences, Birkbeck College, and University College London, Gower Street, London, WC1E 6BT, United Kingdom
AB: Channel geometry exerts a fundamental control on fluvial processes. Recent work has shown that bedrock channel width (W) depends on a number of parameters, including channel slope, and is not only a function of drainage area (A) as is commonly assumed. The present work represents the first attempt to investigate the consequences, for landscape evolution, of using a static expression of channel width (W ~ A^0.5) versus a relationship that allows channels to dynamically adjust to changes in slope. We consider different models for the evolution of the channel geometry, including constant width-to-depth ratio (after Finnegan et al., Geology, v. 33, no. 3, 2005), and width-to-depth ratio varying as a function of slope (after Whittaker et al., Geology, v. 35, no. 2, 2007). We use the Channel-Hillslope Integrated Landscape Development (CHILD) model to analyze the response of a catchment to a given tectonic disturbance. The topography of a catchment in the footwall of an active normal fault in the Apennines (Italy) is used as a template for the study. We show that, for this catchment, the transient response can be fairly well reproduced using a simple detachment-limited fluvial incision law. We also show that, depending on the relationship used to express channel width, initial steady-state topographies differ, as do transient channel width, slope, and the response time of the fluvial system. These differences lead to contrasting landscape morphologies when integrated at the scale of a whole catchment. Our results emphasize the importance of channel width in controlling fluvial processes and landscape evolution. They stress the need for using a dynamic hydraulic scaling law when modeling landscape evolution, particularly when the uplift field is non-uniform.
DE: 1804 Catchment
DE: 1815 Erosion
DE: 1825 Geomorphology: fluvial (1625)
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
SC: Hydrology [H]
MN: 2007 Fall Meeting