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Abstract
Fences and mulch contribute to the spread of wildland-urban interface fires, acting both as ignition targets and as sources that may ignite nearby objects through direct flame contact and firebrand generation. This paper presents the findings from outdoor experiments that investigated the spread of fire through firebrand spotting from fences and mulch beds near a structure in a wind field. A fence section, mulch bed, or combination was arranged perpendicular to a small structure, with a large fan directing wind toward the structure. After ignition, data were collected on firebrand spotting time, time for the spot fire to reach the wall, and flame spread rate over the fence and mulch bed. Fence type, wind speed, and type of mulch were found to affect firebrand spotting. For fence and mulch combinations, spotting usually occurred within 7 minutes. Time to spotting generally decreased with increasing wind speed. Two parallel fence panels burned significantly more intensely, and spotted more quickly, than a single fence panel. In the absence of mulch, spotting from fences often occurred more slowly or not at all. The combination of a fence and a mulch bed decreased the time to spotting over either the mulch bed or the fence alone.
Parent Publication
Citation
Butler, Kathryn M.; Johnsson, Erik L.; Tang, Wei. 2020. Structure vulnerability to firebrands from fences and mulch. In: Hood, Sharon M.; Drury, Stacy; Steelman, Toddi; Steffens, Ron, [eds.]. Proceedings of the Fire Continuum-Preparing for the future of wildland fire; 2018 May 21-24; Missoula, MT. Proceedings RMRS-P-78. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 31-43.
