HR: 17:45h
AN: H44B-08    [Abstracts]
TI: Numerical and Physical Modeling of Width Dynamics on Fluvial Fans
AU: * Nicholas, A
EM: A.P.Nicholas@exeter.ac.uk
AF: Department of Geography, University of Exeter, Amory Building, Rennes Drive, Exeter, EX4 4RJ, United Kingdom
AU: Quine, T
EM: T.A.Quine@exeter.ac.uk
AF: Department of Geography, University of Exeter, Amory Building, Rennes Drive, Exeter, EX4 4RJ, United Kingdom
AU: Clarke, L
EM: Lucy.E.Clarke@exeter.ac.uk
AF: Department of Geography, University of Exeter, Amory Building, Rennes Drive, Exeter, EX4 4RJ, United Kingdom
AU: Olley, J
EM: jon.olley@csiro.au
AF: CSIRO Land and Water, GPO Box 1666, Canberra, ACT 2601, Australia
AB: This paper addresses two main questions: 1) How sensitive are numerical models of fluvial landform evolution to their representation of flow width and its dynamic adjustment? 2) What are the implications of this sensitivity for our understanding of relationships between environmental change and landform evolution? These questions are examined in the particular context of alluvial fans formed by fluvial processes. We present a new model of non-equilibrium flow width on fluvial fans and evaluate its performance using results from a physical modelling study of fan formation. Our results demonstrate that this new model captures the essential controls on, and spatial and temporal changes in, flow width more successfully than existing fluvial width treatments that are commonly used in landform evolution models. We then implement this new representation of flow width within a numerical model of fan evolution in order to assess the potential for using geomorphic evidence (fan morphology and fluvial surface ages) to reconstruct past environmental boundary conditions (water and sediment supply, tectonics and base level change). Multiple (c. 50,000) numerical simulations, conducted within an uncertainty framework, are evaluated using field evidence obtained for small (length c. 1 km), coarse-grained alluvial fans in the Southern Alps, New Zealand. Results demonstrate the potential for width dynamics to drive strong positive feedbacks during fan evolution and promote equifinality in fan morphology.
DE: 1807 Climate impacts
DE: 1825 Geomorphology: fluvial (1625)
DE: 1847 Modeling
DE: 1873 Uncertainty assessment (3275)
SC: Hydrology [H]
MN: 2007 Fall Meeting