Is the existing WUI mapping adequate for wildland fire management? Assessment with past wildfire events

Abstract:

Past studies identified the cultural aspect of the human inclination to live in close proximity to the natural amenities provided by forested lands and mountainous regions. Due to the increasing number of houses near or within the forest since the mid-1900s, there has been a drastic growth in the Wildland-Urban Interfaces (WUI), which are regions where human settlements meet or overlap the wildland vegetation. There is a perception that damages due to wildfire events are mainly located at the WUI. However, a recent study showed that on overlapping the area of fire perimeters with the buildings from 2000 to 2013 in California (CA), only 1.1% (1,398 sq. km) of the buildings were destroyed within the WUI, while this number grew to 34% (4,1262 sq. km) within the Non-WUI. Here, we report the actual occurrences of wildfire events with respect to WUI in CA both in terms of area burned and fire ignition. We have used two types of WUI datasets, namely, WUI-A from Martunizzi et al. (2015) and WUI-B from CAL FIRE (Fire and Resource Assessment Program (FRAP), 2015). Fire ignition points and fire perimeter data from MTBS (Monitoring Trends in Burn Severity) for 2010 - 2017 have been used . The percentage of wildfires ignited in WUI-A ranges from 3.6% inside the WUI area to 66% within a 5 km buffer distance from the WUI, while this range varies from 1.2% to 45.6% in WUI-B. Moreover, only 0.4% of the WUI-A in CA has been located on planar areas, while 99.6% of the WUI-A are situated on complex topography. Interestingly, 6.9% of the WUI-A are on very complex topography. Therefore, wildfires are not limited to WUI regions only, but it increases and causes more damages farther away from the WUI, and are more located on the complex topography in CA. Results from this study will be helpful for the wildfire management and would benefit the policymakers and land managers at the state and local level to focus on the factors that determine the high-risk prone areas for future wildfires.