Flatland in flames: a two-dimensional crown fire propagation model

Abstract

The canopy bulk density metric is used to describe the fuel available for combustion in crown fire models. We propose modifying the Van Wagner crown fire propagation model, used to estimate the critical rate of spread necessary to sustain active crown fire, to use foliar biomass per square metre instead of canopy bulk density as the fuel input. We tested the efficacy of our proposed model by comparing predictions of crown fire propagation with Van Wagner’s original data. Our proposed model correctly predicted each instance of crown fire presented in the seminal study. We then tested the proposed model for statistical equivalence to the original Van Wagner model using two contemporary techniques to parameterize canopy bulk density. We found the proposed and original models to be statistically equivalent when canopy bulk density was parameterized using the method incorporated in the Fire and Fuels Extension to the Forest Vegetation Simulator (difference < 0.5 km h^–1, α = 0.05, n = 2626), but not when parameterized using the method of Cruz and others. Use of foliar biomass per unit area in the proposed model makes for more accurate and easily obtained fuel estimates without sacrificing the utility of the Van Wagner model.