Characterization of Fuel Properties and Fire Spread Rates for Little Bluestem Grass

Abstract

Rapid urban sprawl and population decentralization in recent decades have increased the size of the wildland-urban interface and resulted in higher community risk and vulnerability to wildfire. This paper primarily focuses on understanding grass-fueled fires common to Texas and improving the understanding of the physics and fire dynamics that are inherent in the grassland and prairie flame spread problem. Little bluestem (Schizachyrium scoparium) grass was chosen as the grassland fuel due to its prevalent coverage in the Texas area and its relevance to grassland fires in Texas. The methodology in this study relies on a framework to characterize fuel properties of little bluestem grass using small- and intermediate-scale experiments to better predict full-scale fire behavior. An intermediate-scale numerical flame spread model was developed for grass fuels that accounts for fuel moisture content to calculate the mass versus time of a burning little bluestem plant. The results of the small- and intermediate-scale experiments were used to develop input parameters for a field-scale numerical simulation of a grass field using a physics-based computational fire model, Wildland-urban interface Fire Dynamics Simulator (WFDS). A sensitivity analysis was performed to determine the effect of varying WFDS input parameters on the fire spread rate. The results indicate that the fuel moisture content had the most significant impact on the fire spread rate.