HR: 08:00h
AN: NG31A-01 INVITED    [Abstracts]
TI: Joint modeling of human dwellings and the natural ecosystem at the wildland-urban interface helps mitigation of forest-fire risk
AU: * Ghil, M
EM: ghil@lmd.ens.fr
AF: AOS Department and IGPP, UCLA, 405 Hilgard Ave., Los Angeles, CA 90095-1565, United States
AU: * Ghil, M
EM: ghil@lmd.ens.fr
AF: ERTI, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75231-05, France
AU: Spyratos, V
EM: spyratos@clipper.ens.fr
AF: ERTI, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75231-05, France
AU: Bourgeron, P S
EM: patrick.bourgeron@colorado.edu
AF: INSTAAR, University of Colorado, UCB 450, Boulder, CO 80309, United States
AB: The late summer of 2007 has seen again a large number of catastrophic forest fires in the Western United States and Southern Europe. These fires arose in or spread to human habitats at the so-called wildland-urban interface (WUI). Within the conterminous United States alone, the WUI occupies just under 10 percent of the surface and contains almost 40 percent of all housing units. Recent dry spells associated with climate variability and climate change make the impact of such catastrophic fires a matter of urgency for decision makers, scientists and the general public. In order to explore the qualitative influence of the presence of houses on fire spread, we considered only uniform landscapes and fire spread as a simple percolation process, with given house densities d and vegetation flammabilities p. Wind, topography, fuel heterogeneities, firebrands and weather affect actual fire spread. The present theoretical results would therefore, need to be integrated into more detailed fire models before practical, quantitative applications of the present results. Our simple fire-spread model, along with housing and vegetation data, shows that fire-size probability distributions can be strongly modified by the density d and flammability of houses. We highlight a sharp transition zone in the parameter space of vegetation flammability p and house density d. The sharpness of this transition is related to the critical thresholds that arise in percolation theory for an infinite domain; it is their translation into our model's finite-area domain, which is a more realistic representation of actual fire landscapes. Many actual fire landscapes in the United States appear to have spreading properties close to this transition zone. Hence, and despite having neglected additional complexities, our idealized model's results indicate that more detailed models used for assessing fire risk in the WUI should integrate the density and flammability of houses in these areas. Furthermore, our results imply that fire proofing houses and their immediate surroundings within the WUI would not only reduce the houses' flammability and increase the security of the inhabitants, but also reduce fire risk for the entire landscape.
UR: http://www.environnement.ens.fr/
DE: 0493 Urban systems
DE: 0515 Cellular automata
DE: 4425 Critical phenomena
DE: 4460 Pattern formation
DE: 4468 Probability distributions, heavy and fat-tailed (3265)
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting