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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-312
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
11 Sep 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Hydrometeorological conditions preceding wildfire, and the subsequent burning of a fen watershed in Fort McMurray, Alberta, Canada
Matthew C. Elmes1, Dan K. Thompson2, James H. Sherwood1, and Jon S. Price1 1Dept. of Geography and Environmental Management, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
2Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, 5320 122 Street Northwest Edmonton, Alberta, Canada, T6H 3S5
Abstract. The destructive nature of the ~ 590,000 ha Horse River Wildfire in the Western Boreal Plain (WBP), northern Alberta in May of 2016 motivated the investigation of the hydrometeorological conditions that preceded the fire. Historical climate and field hydrometeorological data from a moderate-rich fen watershed were used to identify a) whether the spring 2016 conditions were outside the range of natural variability for WBP climate cycles; b) explain the observed patterns in burn severity across the watershed; and c) identify whether fall and winter moisture signals observed in peatlands and lowland forests in the region are indicative of fire susceptibility. Field hydrometeorological data from the fen watershed confirmed the presence of cumulative moisture deficits prior to the fire. Hydrogeological investigations highlighted the susceptibility of fen and upland areas to water table and soil moisture decline over rain-free periods (including winter), due to the watershed's reliance on supply from localized flow systems originating in topographic highs. Subtle changes in topographic position led to large changes in groundwater connectivity, leading to greater organic soil consumption in wetland margins and at high elevations. The 2016 spring moisture conditions measured prior to the ignition of the fen watershed were not illustrated well by the Drought Code (DC) when standard overwintering procedures were applied. However, close agreement was found when default assumptions were replaced with measured duff soil moisture recharge and incorporated into the overwintering DC procedure. We conclude that accumulated moisture deficits dating back to the summer of 2015 led to the dry conditions that preceded the fire. The infrequent coinciding of several hydrometeorological conditions, including low autumn soil moisture, a modest snowpack, lack of spring precipitation, and high spring air temperatures and winds, ultimately led to the Horse River wildfire spreading widely and causing observed burn patterns. Monitoring soil moisture at different land classes and watersheds would aid management strategies in the production of more accurate overwintered DC calculations, providing fire management agencies early warning signals ahead of severe spring wildfire seasons.

Citation: Elmes, M. C., Thompson, D. K., Sherwood, J. H., and Price, J. S.: Hydrometeorological conditions preceding wildfire, and the subsequent burning of a fen watershed in Fort McMurray, Alberta, Canada, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-312, in review, 2017.
Matthew C. Elmes et al.
Matthew C. Elmes et al.

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Elmes et al. (NHESS) Data.zip
M. C. Elmes, D. K. Thompson, J. H. Sherwood, and J. S. Price
https://doi.org/10.6084/m9.figshare.5346484
Matthew C. Elmes et al.

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Short summary
The infrequent coinciding of several hydrometeorological conditions common to the Western Boreal Plain, including low autumn soil moisture, modest snowpack, lack of spring precipitation, and high spring air temperatures and winds, ultimately led to the widespread Horse River Fire in May of 2016. Monitoring antecedent soil moisture would aid management strategies in producing of more accurate overwintered drought code calculations, providing early warning signals ahead of spring wildfire seasons.
The infrequent coinciding of several hydrometeorological conditions common to the Western Boreal...
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