Coupled Assessment of Fire Behavior and Firebrand Dynamics

Jan C. Thomas,Rory M. Hadden,Nicholas Skowronski,Eric V. Mueller,Michael R. Gallagher,Kenneth L. Clark,Albert Simeoni

doi:10.3389/fmech.2021.650580

Abstract

The hazards associated with firebrands have been well documented. However, there exist few studies that allow for the hazard from a given fire to be quantified. To develop predictive tools to evaluate this hazard, it is necessary to understand the conditions that govern firebrand generation and those that affect firebrand deposition. A method is presented that allows for time-resolved measurements of fire behavior to be related to the dynamics of firebrand deposition. Firebrand dynamics were recorded in three fires undertaken in two different ecosystems. Fire intensity is shown to drive firebrand generation and firebrand deposition—higher global fire intensities resulting in the deposition of more, larger firebrands at a given distance from the fire front. Local firebrand dynamics are also shown to dominate the temporal firebrand deposition with periods of high fire intensity within a fire resulting in firebrand shower at deposition sites at times commensurate with firebrand transport. For the range of conditions studied, firebrand deposition can be expected up to 200 m ahead of the fire line based on extrapolation from the measurements.

Highlights

The hazards associated with firebrands as the leading cause of structure ignitions in fires at the wildland–urban interface and as a fire spread vector are well documented (Caton et al, 2017; Hakes et al, 2017; Manzello et al, 2020))
Despite a large number of studies in recent years aimed at reproducing firebrand exposures for material testing (Manzello et al, 2008; Manzello and Suzuki, 2013; Thomas et al, 2018), identifying the ignition hazard posed by firebrands and firebrand accumulations (Manzello et al, 2017; Fernandez-Pello, 2017; Matvienko et al, 2018; Hakes et al, 2019), and the development of numerical models (Wadhwani et al, 2017), there exists very little information on firebrand exposures from wildland fires which captures the link between the dynamic quantities of firebrand deposition and fire behavior
The hazard associated with firebrand exposure is a complex coupling of fire behavior, fuels, and environmental factors

Summary

Introduction

The hazards associated with firebrands as the leading cause of structure ignitions in fires at the wildland–urban interface and as a fire spread vector are well documented (Caton et al, 2017; Hakes et al, 2017; Manzello et al, 2020)). The primary sources of firebrand deposition data are generally associated with investigations carried out after large fires of special interest (Maranghides and Mell, 2011), or measurements of firebrand deposition after prescribed fires (El Houssami et al, 2016a; Filkov et al, 2017; Thomas et al, 2017). Such approaches have been limited in allowing the firebrand hazard to be quantified in terms of an integrated firebrand deposition and particle size distributions only.

Methods

Results

Conclusion