AINSWORTH, Sarah - 2005
GIS Assessment of the Impacts of Hurricane Juan on Forest Fire Hazard
Multi-criteria evaluation was incorporated into a GIS framework to examine forest fire hazard areas within south central Nova Scotia pre and post-Hurricane Juan. Hazard parameters (forest cover, blowdown areas, slope, aspect and proximity to communities) were assigned values, standardized and weighted. Multi-criteria algorithms were applied to the pre and post-Juan data and values were then ranked and reclassified into an appropriate classification scheme representing forest fire hazard. The final index ranges from zero to four. Zero represents no hazard (e.g. water) and one, two, three and four represent low, moderate, high and very high hazard, respectively. The final hazard index pre-Juan was similar to the post-Juan map when low, moderate and high categories of hazard were compared. The values only slightly decreased from pre-to post-Juan. The hazard category with the greatest change between the two indices was the very high category. Before the hurricane, very high hazard represented 0.02% of the study site, whereas after the hurricane this number increased to 2%. This change represents approximately 22 km2 of the study site, suggesting that the blowdown areas from the hurricane increased the hazard across the study site.
Fire occurrence data were used to examine the location and spatial arrangement of fires with the proximity to communities parameter. It is shown that the greatest number of fires (66.7%) existed closest to the populated areas of the study site and the number of fires decreased with each successive distance from these areas. An explanation for this can be related to the cause of the fires, whereas the majority of causes within the study site are human related. Fire occurrence data based on the area burned was also mapped with forest cover, slope and aspect to examine the influence of these parameters on fire spread. The most flammable forest cover had the greatest number of fires (43) as well as total hectares burned (27.2). However, the mean value of area burned was only the second highest of all forest cover types. The least flammable forest cover type had the lowest number of fires (6) but the second highest number of hectares burned (7.3). Slope classified as moderate had the greatest mean value for hectares burned (1.0), followed by the low slope class (0.6) and then the high slope class (0.1). Mean hectares burned was slightly higher for aspects classified as low (0.8) followed by moderate (0.6) and high aspects (0.5). Proximity to communities, forest cover, slope and aspect were examined with fire occurrence data to help validate the choice of these parameters in creating the fire hazard index.
This research will help to identify areas where fires are likely to ignite and spread by mapping the location of fires and total area burned within the study site. Most important, the forest fire hazard index will help to outline the location and spatial extent of each degree of hazard pre and post-Juan. The hazard index will be useful to forest fire management as it provides a spatial representation of the impacts of Hurricane Juan on forest fire hazard within Nova Scotia.