No abstract

An experimental approach has been developed to quantify the characteristics and flux of firebrands during a management-scale wildfire in a pine-dominated ecosystem. By characterizing the local fire behavior and measuring the temporal and spatial variation in firebrand collection, the flux of firebrands has been related to the fire behavior for the first time. This linkage is seen as the first step in risk mitigation at the wildland urban interface (WUI). Data analyses allowed the evaluation of firebrand flux with respect to observed fire intensities for this ecosystem. Typical firebrand fluxes of 0.824-1.361 pcs.m -2 .s -1 were observed for fire intensities ranging between 7.35±3.48 MW.m -1 to 12.59±5.87 MW.m -1 . The experimental approach is shown to provide consistent experimental data, with small variations within the firebrand collection area. Particle size distributions show that small particles of area 0.75-5×10 -5 m 2 are the most abundant (0.6-1 pcs.m -2 .s -1 ), with the total flux of particles >5 ×10 -5 m 2 equal to 0.2 to 0.3 pcs.m -2 .s -1 . The experimental method and the data gathered show substantial promise for future investigation and quantification of firebrand generation and consequently a better description of the firebrand risk at the WUI.

This study aims to develop a series of robust and efficient methodologies, which can be applied to understand and estimate firebrand generation and to evaluate firebrand showers close to a fire front. A field scale high intensity prescribed fire was conducted in the New Jersey Pine Barrens in March 2013. Vegetation was characterised with field and remotely sensed data, fire spread and intensity was characterised and meteorological conditions were monitored before and during the burn. Firebrands were collected from different locations in the forest and analysed for mass and size distribution. The majority were found to be bark slices (more than 70%) with substantial amounts of pine and shrub twigs. Shrub layer consumption was evaluated to supplement the firebrand generation study. Bark consumption was studied by measuring the circumference variation at several heights on each of three different pine trees. The variation was in the same order of magnitude as the bark thickness (1-5 mm). Testing and improving the protocol can facilitate the collection of compatible data in a wide range of ecosystems and fire environments, aiding in the development of solutions to prevent structural ignition at the Wildland Urban Interface.

Quantification of field-scale fire behavior is necessary to improve the current scientific understanding of wildland fires and to develop and test relevant, physics-based models. In particular, detailed descriptions of individual fires are required, for which the available literature is limited. In this work, two such field-scale experiments, carried out in pine stands under mild conditions, are presented. A particular focus was placed on non-intrusive measurement, as the capabilities of advanced remote sensing techniques, along with more traditional approaches, are explored. A description of the fires is presented, with spread occurring predominantly in the surface fuels with intensities in the range of 200-4400 kW•m -1 , and punctuated by isolated regions of crown fire. The occurrence of crown fire is investigated and linked to regions of greater canopy density, and it is found that the total fire intensity may increase locally to as much as 21000 kW•m -1 . The light winds do not appear to play a direct role in the changes in fire behavior, while fuel structure may be important. The measurements described herein provided a reasonable overall description of the fires, however, the current resolution (both spatial and temporal) falls short of definitively explaining some transitional aspects of the fire behavior, and future improvements are suggested.