Modelling the probability of sustained flaming: predictive value of fire weather index components compared with observations of site weather and fuel moisture conditions

Abstract

We investigated the likelihood that short-duration sustained flaming would develop in forest ground fuels that had direct contact with a small and short-lived flame source. Data from 1027 small-scale experimental test fires conducted in field trials at six sites in British Columbia and the North-West Territories between 1958 and 1961 were used to develop logistic regression models for ten fuel categories that represent unique combinations of forest cover, ground fuel type, and in some cases, season. Separate models were developed using two subsets of independent variables: (1) weather variables and fuel moisture measurements taken at the site of the test fire; and (2) Canadian Fire Weather Index (FWI) system components calculated from weather observations recorded at a nearby station. Results indicated that models developed with FWI system components were as effective as models developed with site variables at predicting the probability of short-duration sustained flaming in most fuel categories. FWI system components were not useful for predicting sustained flaming in spring grass fuels and had limited usefulness for modelling the probability of sustained flaming in aspen leaf ground fuels during summer conditions. For all other fuel categories, FWI system components were highly effective substitutes for site variables for modelling the probability of sustained flaming.

Defining fire spread event days for fire-growth modelling

“…This significance of DMC (and consequently BUI) may indicate an effect of forest-floor consumption effectively raising surfacefire intensity and consequently raising the amount of crown engaged in flaming. It may also be a signal of the influence of surface organic layer moisture (as DC was not significant) on litter moisture content; such an effect was observed and quantified by Beverly and Wotton (2007).…”

“…The Canadian Forest Fire Weather Index System or FWI System (Van Wagner 1987), used to assess fire danger, describes moisture in key forest-floor layers, and provides three fuel-type-independent relative indicators of potential forest fire behaviour. The moisture content of surface litter is characterised by the Fine Fuel Moisture Content (FFMC) and is important for determining the sustainability and vigour of surface fire spread (Lawson and Armitage 1997;Beverly and Wotton 2007). The moisture content of the upper portion of the organic layer in the forest floor is tracked by the Duff Moisture Code (DMC) and is important to sustainability of smouldering and fuel consumption in the forest floor (Van Wagner 1972a).…”

Surface fire spread potential in trembling aspen during summer in the Boreal Forest Region of Canada

“…For that time of year, the DMC and DC levels reflect a relatively warm and extended dry spell following snow melt in the spring (Table 2). Beverly and Wotton (2007) re-analyzed some of the data on the 2-minute test fires carried out in different fuel types by the federal forest service fire research group (Paul 1969, Simard 1970 in the late 1950s and early 1960s for the purposes of developing regional fire danger rating tables (e.g., Kiil and Mactavish 1962). This included an "aspen leaf (summer)" site near Fort Smith, Northwest Territories, described as a "Pure, 60-year old even-aged trembling aspen stand with a basal area of ~22 m 2 per hectare.…”

Ignition probability of fine dead surface fuels of native Patagonian forests or Argentina

“…Small-scale, experimental test f ires, modeling ignition processes, have been successfully applied in numerous researches in Canada and elsewhere using either laboratory apparatus or field ignition trials (De Groot et al, 2005;Tanskanen et al, 2005). These small experimental fires are inexpensive, can be conducted under controlled laboratory conditions, with minimal disruption of field site and with less risk (Frandsen, 1997;Beverly and Wotton, 2007), avoiding external factors influencing the ignition (mostly weather and site characteristics).…”