A fundamental look at fire spread in California chaparral

Abstract

The USDA Forest Service National Fire Plan funded a research program to study fire spread in live fuels of the southwestern United States. In the U.S. current operational fire spread models do not distinguish between live and dead fuels in a sophisticated manner because the study of live fuels has been limited. The program is experimentally examining fire spread at 3 scales – the fuel element, the fuel bed, and field scale. Data from the experimental work is being used to test and improve operational (BEHAVE) and research fire spread models (PAGNI, FIRETEC/HIGRAD). The principal live fuels studied are chamise (Adenostoma fasciculatum), manzanita (Arctostaphylos parryana), ceanothus (Ceanothus crassifolius), and scrub oak (Quercus berberidifolia). The effects of fuel element orientation and moisture content on time to ignition in a convective environment have been studied to date. We have burned 190 single species fuel beds to study the effects of fuel bed density, fuel moisture content, wind speed (0, 2 m s^-1), and fuel bed slope on fire spread success. A thermal imaging technique to estimate velocities in the flame has been developed. Results to date reaffirm the importance of moisture in combustion in live fuels. The importance of wind and slope on fire spread success has been demonstrated and is being described empirically. Wind velocity of 2 m s^-1 has been sufficient to cause fire spread success in live fuel beds with moisture content > 80% dry weight basis. Results of the fuel element, fuel bed, and model testing work are presented.

Citation

Weise, David R.; Fletcher, Thomas; Baxter, Larry; Mahalingam, Shankar; Zhou, Xiangyang; Pagni, Patrick; Linn, Rod; Butler, Bret. 2004. A fundamental look at fire spread in California chaparral. Pp. 186-193 in Proceedings of 11th Annual AFAC Conference and Inaugural Bushfire CRC Conference 7-9 October 2004 Perth, Western Australia. (CD-ROM)