4.4 Hazards related to vegetation/fuel conditions surrounding homes Natural and landscaped vegetation provides many of the valued amenities of living in a WUI community. At the same time, vegetation provides fuel that makes it possible for wildfires to spread into and though urban areas. FireSmart guidelines identify treatments to modify the location, amount, composition, and burning characteristics of vegetation fuels. In particular, the horizontal and vertical continuity of fuel dictates wildfire behavior. Collectively, these treatments promote lowered fire intensity and greatly reduce the potential for homes to ignite if they are implemented. 4.4.1 Contribution of vegetation/fuel hazard by FireSmart Priority Zone In order to achieve risk reduction objectives, maintaining FireSmart vegetation guidelines in each of the three concentric Priority Zones is essential. Guidelines become progressively more stringent as the distance to the home decreases.
Table 4-6: Hazard points and percentage of vegetation/fuel hazard attributed to Priority Zones Priority Zone vegetation/fuel Study site
Priority Zone 1 (max. 80 points)
Priority Zone 2 (max. 70 points)
Priority Zone 3 (max. 55 points)
Points7
%10
Points7
%10
Points7
%10
Slave Lake Rural
3.1
14.1
8.5
38.4
10.5
47.5
Slave Lake Urban
2.3
56
1.1
26.7
0.7
17.3
Kelowna Rural
16.3
38.3
14.4
33.9
11.8
27.8
Kelowna Urban
17.3
49
10.5
30
7.4
21
Overall Average
9.7
40
8.6
32
7.6
28
Key results: By far, vegetation was the leading contributor to critically high levels of wildfire hazard at private residences studied in Kelowna, and levels of FireSmart adoption were very poor. In contrast, the degree of FireSmart compliance by homeowners was excellent at Slave Lake, and vegetation related hazards low. In urban areas, vegetation conditions closest to the home consistently accounted for the majority of fuel hazards. Priority Zone-1: Priority Zone-1 extends outwards for a distance of 10m from the outer walls of a structure. It is the most critical zone for treating vegetation to reduce home ignition potential. In the dense urban settings of Slave Lake and Kelowna it was common for the Priority Zone-1s of adjacent homes to overlap. Recommended guidelines focus on removal, reduction, and conversion of vegetation in this zone.
10
Percent of the total hazard attributed to vegetation/fuel in Priority Zones 1, 2, and 3.
30