Quantitative framework for soil burn severity from numerical wildfire models

Abstract

Soil burn severity is a critical impact of wildfires. A numerical model of fire physics links heat flux and temperature to soil burn severity and follow-on hydrological effects. Numerical results for an example catchment-scale application demonstrate a high likelihood of severe burn for most of the region and the degree of soil alteration. The fire persists for an average of approximately 60 min for most of the area. Translation of peak heat fluxes to temperature showed that most of the soil in the fire scar was exposed to temperatures as high as 800–900 °C. The energy balance analysis revealed that soil moisture content decreases on average from 0.234 m³/m³ to 0.177 m³/m³ in the wildfire scar. The translation of peak heat flux into peak temperature and integration with Soil Organic Matter (SOM) shows that most near-surface SOM constituents are volatilized during the passage of the fire.