Flame-Front Rate of Spread Estimates for Moderate Scale Experimental Fires Are Strongly Influenced by Measurement Approach

Joshua Johnston,Martin Wooster,Ronan Paugam,Melanie Wheatley,G Davies,Kaitlin Deboer

doi:10.3390/fire1010016

Abstract

Understanding wildfire rate of spread (RoS) is often a key objective of many fire behavior modelling and measurement exercises. Using instrumented moderate scale laboratory burns we provide an assessment of eight different methods of flame front RoS determination, including visible imagery (VIS) analysis techniques, use of thermocouple arrays, and four thermal infrared (IR) image analysis approaches. We are able to (1) determine how measurement approach influences derived RoS, and (2) recommend the best method to reproduce the accepted standard (Thermocouple Grid Array measurement) RoS without ground sampling. We find that derived RoS is statistically significantly influenced by the measurement approach, and that failing to fully account for directionality of the RoS may result in significant error. We identify one of the thermal infrared imaging methods (described in Paugam et al. 2013), as the most appropriate for providing rate and direction of spread at these scales of measurement.

Highlights

Wildfire behavior can be described as the manner in which a spreading fire reacts to changes in its environment with respect to fuels, topography, and weather
For (b), burns are identified by date and “Bi ” to indicate burn number (e.g., i = 1, 2, 3, ...). (c) Boxplot of all rate of spread (RoS)
This study suggests that the method used to determine RoS has a significant impact on the derived values at the type of moderate-scale experimental fires used

Summary

Introduction

Wildfire behavior can be described as the manner in which a spreading fire reacts to changes in its environment with respect to fuels, topography, and weather. Changes in wildfire behavior have substantial impacts on the safety of fire suppression operations and the tactics that must be employed [1]. The primary indicators of fire behavior are rate of spread (RoS) and Byram’s fire intensity (FI; [2,3,4]). RoS determination is an important area of wildfire research [5,6,7,8], and often the primary objective of many fire measurement and behavior modelling exercises [9,10,11]. The importance of RoS extends to its operational use, as it is crucial for assessing the safety of ground crews responding to wildfire [1,12,13,14,15]

Methods

Results

Conclusion