Empirical Modeling of Fire Spread Rate in No-Wind and No-Slope Conditions

Fire spread rate in the absence of wind or slope is a function of fuel characteristics and a reasonable surrogate for backfire spread, which is representative of relevant sections of wildfire fronts. We developed two simple empirical functions for estimating fire spread rate under windless conditions in flat terrain, using a total of 421 fires (laboratory and field experiments, and wildfires) for model fitting and evaluation. The first model is based on fuel bed moisture content and height. The second model adds fuel particles' surface area-to-mass ratio to the independent variables, allowing extension to a broader variety of fuel types, namely grass; model comparisons using evaluation data indicated improved prediction ability in relation to the widely used Rothermel model. The models are based on a comprehensive group of burn experiments in highly diverse fuel beds, warranting further inspection of the approach for both scientific development and management applications.