Testing the utility of terrestrial laser scanning for fuel hazard assessments in temperate forests and woodlands of south-eastern Australia

Abstract Background Fire managers routinely assess fuels to predict fire behavior and assess the efficacy of fuel treatments. Terrestrial laser scanning (TLS) has the potential to provide a new source of detailed field data that can be interrogated to characterize fuel. This study examined the potential for integrating phase-shift TLS data into fuel hazard assessments in temperate south-eastern Australia by comparing measures of fuel properties and hazard scores from a manual “extended” method (an extension of an operationally implemented fuel hazard assessment) with those from a “TLS-plus” method (phase-shift TLS data plus select manual field measures). The two methods were tested in 42 plots of mature eucalypt forest or woodland across a broad landscape. Results The TLS-plus method led to higher estimates of mean cover for near-surface and elevated fuel (14 and 21% more, respectively), which resulted in fuel hazard scores up to 3 levels higher (on a scale of 1 to 5) than the extended method. The magnitude difference in cover estimates between the TLS-plus and extended method was most strongly related to plot-specific differences in vegetation cover rather than landscape variations in vegetation composition and structure. Conclusions This study indicates that phase-shift TLS has only limited utility for assessing fuel hazard in structurally complex native temperate forests as it needs to be supported by many in-field measures to interpret fuel hazard. Furthermore, higher cover estimates produced by the TLS-plus method will elevate predictions of fire behavior compared to the extended method under the same vegetation conditions (i.e., faster rates of spread, higher flame heights). These higher estimates are partially due to systematic bias introduced by the inclusion of coarse fuel by the TLS-plus method that is not included with the extended method. This study indicates that phase-shift TLS has limited utility for assessing fuel hazard in structurally complex native temperate forests as it needs to be supported by many in-field measures to interpret fuel hazard. Beyond fuel hazard assessment, TLS technology has the potential to provide more quantitative and sophisticated measures of fuel that will likely make it a trusted source of data for fire managers, especially for evaluating fuel management actions.