HR: 0800h
AN: H31A-1261    [Abstracts]
TI: Modeling River Incision Across Active Normal Faults Using the Channel-Hillslope Integrated Landscape Development Model (CHILD): the case of the Central Apennines (Italy)
AU: * Attal, M
EM: Mikael.Attal@ed.ac.uk
AF: Institute of Earth Science, School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW United Kingdom
AU: Tucker, G
EM: gtucker@cires.colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences (CIRES) and Dept. of Geological Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Whittaker, A
EM: Alexander.Whittaker@ed.ac.uk
AF: Institute of Earth Science, School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW United Kingdom
AU: Cowie, P
EM: Patience.Cowie@glg.ed.ac.uk
AF: Institute of Earth Science, School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW United Kingdom
AU: Roberts, G
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: River systems constitute some of the most efficient agents that shape terrestrial landscapes. Fluvial incision rates govern landscape evolution but, due to the variety of processed involved and the difficulty of quantifying them in the field, there is no "universal theory" describing the way rivers incise into bedrock. The last decades have seen the birth of numerous fluvial incision laws associated with models that assign different roles to hydrodynamic variables and to sediments. In order to discriminate between models and constrain their parameters, the transient response of natural river systems to a disturbance (tectonic or climatic) can be used. Indeed, the different models predict different kinds of transient response whereas most models predict a similar power law relationship between slope and drainage area at equilibrium. To this end, a coupled field - modeling study is in progress. The field area consists of the Central Apennines that are subject to active faulting associated with a regional extensional regime. Fault initiation occurred 3 My ago, associated with throw rates of 0.3 +/- 0.2 mm/yr. Due to fault interaction and linkage, the throw rate on the faults located near the center of the fault system increased dramatically 0.7 My ago (up to 2 mm/yr), whereas slip rates on distal faults either decayed or remained approximately constant. The present study uses the landscape evolution model, CHILD, to examine the behavior of rivers draining across these active faults. Distal and central faults are considered in order to track the effects of the fault acceleration on the development of the fluvial network. River characteristics have been measured in the field (e.g. channel width, slope, sediment grain size) and extracted from a 20m DEM (e.g. channel profile, drainage area). We use CHILD to test the ability of alternative incision laws to reproduce observed topography under known tectonic forcing. For each of the fluvial incision models, a Monte-Carlo simulation has been performed, allowing the exploration of a wide range of values for the different parameters relative to tectonic, climate, sediment characteristics, and channel geometry. Observed profiles are consistent with a dominantly wave-like, as opposed to diffusive, transient response to accelerated fault motion. The ability of the different models to reproduce more or less accurately the catchment characteristics, in particular the specific profiles exhibited by the rivers, are discussed in light of our first results.
DE: 1804 Catchment
DE: 1815 Erosion
DE: 1824 Geomorphology: general (1625)
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
SC: Hydrology [H]
MN: Fall Meeting 2005