Due to continued outward expansion of industry and community development into the wildland-urban interface (WUI), the threat to life safety and property from wildland fires has become a significant problem. Such fire scenarios can be better understood through the use of computation fluid dynamics based fire-spread models. However, current physical fire models must be specifically adapted to handle the phenomena associated with WUI fires. Only then can they be reliably used as research and decision making tools to help mitigate the problem. In this research, the current standard in wildland fire modeling for representing the effect on wind flow from a porous vegetative medium is examined. The technique used employs basic correlations for object drag, and its validity with respect to real vegetation has yet to be examined in detail by the scientific community. The modeling of vegetation is studied within the framework of the existing Wildland-Urban Interface Fire Dynamics Simulator (WFDS), and the potential need for continued development is assessed. Comparisons are made to both experimental and numerical studies. Additionally, the validity of the model is considered at both the scale of an individual tree, as well as that of a whole forest canopy. Results show that as a first approximation the model is able to perform well in the latter case. At the scale of an individual tree, however, the behavior is governed by theoretical constants. The assumption of cylindrical vegetation elements performs slightly better than the commonly used spherical case, but neither adequately captures experimental tendencies. Accurate flow representation for single trees is crucial to modeling the key driving factors of fire behavior (such as combustion and heat transfer) in small scale WUI scenarios. Ultimately, this study illustrates the need for well-designed experiments, specifically to generate empirical constants which will improve the behavior of the simplified theory.

In conducting this research, I wanted to explore whether political incentives have a significant effect on wildfire management in the United States. I attempt to answer this question by proving a theoretical justification for why wildfires may become more expensive to fight and severe to manage because of political institutions. I then attempt to provide some hard evidence to support this theory by using regression analysis. My analysis suggests that political factors do matter for wildfire suppression funding, although I was unable to find strong enough evidence to suggest that these political factors are actually driving more severe wildfires. This research contributes to the literature on public choice theory, a branch of political economy that looks at government from the individual decision makers’ level. Additionally, this research contributes to the literature on what affects wildfire suppression effectiveness and funding. This research may contribute to future analyses of the institutions that make U.S. wildland firefighters more or less capable of effectively managing wildfires to protect human lives, property, and forests.

Current operational wildland fire models are based on numerous correlations from experiments performed on dry (dead) fuel beds. However, experience has shown distinct differences in burning behaviors between dry and moist (live) fuels. To better understand these fundamental differences, an experiment was designed to use a flat-flame burner to simulate a moving fire front which heated and ignited a stationary, individual fuel sample. Samples included various U.S. species from the California chaparral, the intermountain west, and the southeastern regions. Temperature, mass, and video images were recorded throughout each experimental run from which numerous data values were obtained such as time to ignition, ignition temperature, flame height, time of flame duration, and mass release rates. Qualitative results showed various phenomena such as color change, bubbling, bursting, brand formation, and bending; these phenomena were species-dependent. Quantitative results showed differences in the ignition values (time, temperature, and mass) among species. It was observed that all moisture did not leave the interior of the sample at the time of ignition. Also, from the temperature history profiles, no plateau was observed at 100°C, but instead at 200-300°C. This indicates a need to treat evaporation differently than the classical combustion model. Samples were treated with solvents in attempt to extract the cuticle from the surface. These treated samples were compared to non-treated samples, though no significant combustion characteristics were observed. The time of color change for the treated samples varied significantly, indicating that the cuticle was indeed removed from the surface. Two-leaf configurations were developed and compared to determine combustion interactions between leaves. A second leaf was placed directly above the original leaf. Results showed that the time of flame duration of the upper leaf was significantly affected by the presence of the lower leaf. Causes for the prolonged flame were found to be the consumption of O2 by the lower leaf and the obstruction provided by the lower leaf, creating a wake effect which displaced hot gases from the flat-flame burner as well as entrained surrounding room temperature gas. A semi-physical model based on fluid dynamics and heat and mass transfer was developed that included the observed plateau at 200-300°C, rather than at 100°C; this was done for both the single- and two-leaf configurations. Another model using a statistical approach was produced which described the combustion of a bush that incorporated data obtained from the experimental results. Overall burning times and percentage of fuel consumption were obtained for various fuel loadings using this statistical model.

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