The impact of soil moisture content and particle size variations on heat flow in laboratory simulated wildfires

Hydrophobic soils developing as a consequence of wildfires have a large impact on the environment. A greater understanding of when ideal hydrophobic development conditions occur is needed. This thesis aims to identify the impact of varying both soil moisture and soil particle size on the locations for ideal hydrophobic soil development under different intensities of burns. It builds on experiments completed previously to further the understanding of the effect of particle size on heat flow. All experiments done in the previous study used only dry sediment. This study focused on the role of moisture in hydrophobic soil development. A secondary goal of this thesis is to provide an opportunity to further explore convection as a mechanism of soil heating. An indoor wildfire simulator was employed, consisting of an array of propane burners, to determine the impact of varying factors under controlled conditions. The temperature levels and durations selected were based on data obtained from measurements taken during full-scale field based burns. Thermocouples were used to measure temperatures of the flames and temperatures at different depths within the sediment. Determining the impact of soil texture was done by running burns with sand, clay-loam, silt, and clay. The impact of soil moisture was determined by testing each of the sediment types with different levels of moisture. In total, twenty-four burns were completed with peak temperatures of 600 degrees C, 900 degrees C, and 1200 degrees C in order to simulate typical chaparral fires.