Objective 1 - Vulnerability and Susceptibility Factors
In order to understand the risk behind wildfires, an area's vulnerability to wildfires must be analyzed. The factors that lay behind the vulnerability of an area involve ecological vulnerability, land value, and the potential for loss of life (Tutsch et al., 2010).
Factor 1: Ecological vulnerability
Ecological value and ecosystem services are used to measure the value of land affected by potential wildfires (Tutsch et al., 2010; Chuvieco et al., 2013). The ecological value of land is related and positively correlated with the species at risk and species biodiversity affected within the area (Tutsch et al., 2010). Land with more biodiversity and species-at-risk will be rated higher throughout the analysis than lands with fewer of these variables (Tutsch et al., 2010).
Factor 2: Land value
Human use of the land, land uses types and the ecosystem services it has to offer, have an effect on land value and its potential for economic gains. In a Canadian context, timber land and agricultural land are rated highly due to their potential for economic outputs (Tutsch et al., 2010), whereas park land and cultural heritage sites are rated the next highest value due to their economic value and cultural importance, followed by non-park non-timber forest land (Tutsch et al., 2010). These measures are based on the economic importance as well as their importance to British Colombians overall (Tutsch et al., 2010).
Factor 3: Potential for loss of life
The most important vulnerability factor for consideration is the potential for loss of life (Tutsch et al., 2010). Economic losses and damages to land can be reversed over time, but the loss of human life cannot be recovered (Tutsch et al., 2010). The potential for loss of human life is measured by finding evacuation problem areas and using them to determine the likelihood of loss to human life if a wildfire were to occur (Tutsch et al., 2010). This is significantly related to the remoteness of the communities (Tutsch et al., 2010). More remote communities will be considered at a higher potential for loss of human life, while less remote communities will be considered at a lower potential (Tutsch et al., 2010).
In order to understand the risk involved with wildfire occurrence in an area, an area’s susceptibility to wildfires must be addressed (Calviño Cancela, 2017). The factors involved in determining this susceptibility include the likelihood that an ignition event occurs, the type of fuel at the ignition site and the fuel conditions at the ignited area are of sufficient quantity and quality to create a substantially large wildfire (Duff, 2017).
Wildfire ignition is due to a combination of both natural and anthropogenic causes.
Factor 1: Natural Ignitions
Natural causes, such as lightning vary in terms of ignition due to different elevations and frequency (Guo et al., 2016; Kilinc and Beringer, 2007; Valdez et al., 2017). Frequent strikes of lightning increases the chance of ignition sites resulting in large wildfire potential (Kilinc and Beringer, 2007). Elevation will be the only predictor of natural ignition due to the high predictability and correlation of elevation and lightning occurrence (Kilinc and Beringer, 2007; Guo et al., 2016).
Factor 2: Anthropogenic Ignitions
Anthropogenic ignitions are caused by human activities, and will therefore be measured based on the factor of proximity of humans to the potential wildfire site (Valdez et al., 2017). In previous fire models, a positive correlation has been found between the proximity to humans based on the location to roads, and the likelihood of a wildfire ignition occurring (Valdez et al., 2017). Proximity to roads will be the only anthropogenic ignition factor to be considered since it was found to be the only highly reliable factor for man-made ignition sources (Gralewicz, 2008; Valdez et al., 2017).
Fuel conditions are a function of both the amount of fuel and the moisture content and temperature of the fuel (Woolford et al., 2014). These factors combined will have an influence in the spread of fire and the likelihood of occurrence.
Factor 3 and 4: Maximum Annual Temperature and Mean Annual Precipitation
Drier fuel conditions creates greater chance of wildfires spreading (Woolford et al., 2014). This means that a climate with lower moisture and higher temperatures will result in a greater potential for wildfires (Woolford et al., 2014). The values of maximum annual temperature and mean annual precipitation will be used to represent moisture and temperature conditions.
Factor 5: Biomass
The amount of fuel will be measured based on biomass accumulation. Biomass is a proxy to estimate the amount of accumulated fuel in the area for both canopy and dead matter (Reinhardt et al., 2008; Thompson et al., 2017). Areas with low fire disturbance will have large fuel accumulations of biomass in comparison to high fire disturbance areas (Reinhardt et al., 2008; Thompson et al., 2017).
The fuel type is divided into the percentage of dead fuel to live fuel in the area, as well as the age and type of existing stands.
Factor 6: Ratio of Dead to Alive Biomass
Dead fuel is much more likely to spread fire than live fuel; therefore, wildfire susceptibility will increase with the quantity of dead fuel in the area (Thompson et al., 2017).
Factor 7: Stand Age
The age of tree stands is also correlated with their flammability, with older tree stands being more susceptible to fires than younger ones (Thompson et al., 2017). This is in large part due to the lower moisture content of older tree stands, which results in a higher flammability potential than high moisture young stands (Thompson et al., 2017).
Factor 8: Stand Type
The type of stand also affects the risk of fire, with coniferous forests being more likely to burn than deciduous forests (Renkin and Despain, 1991; Beverly et al., 2009). Renkin and Despain (1991) state that Douglas-fir and lodgepole-pine, a coniferous species, are less likely to burn than the Engleman-spruce, a deciduous species common to the study area. This results in an increased chance of burning in forests consisting of Engleman-spruce compared to those mainly consisting of coniferous trees. The relative flammability of stand type from most to least flammable values were based on the findings of Beverly et al. (2009) Renkin and Despain (1991) (Table 6).
Constraints: Water Bodies and Areas Without Vegetation
Water bodies and areas without vegetation cannot be affected by wildfires since they cannot burn. Areas without vegetation can be determined by areas that are either barren surfaces or highly developed urban areas with little to no vegetation.