Fire exposure and vulnerability of wildland-urban interfaces: a case study from Northern Sardinia, Italy

In this work, we analyzed fire exposure and vulnerability of a 46,000 ha study area located in North-East Sardinia. The study area is very prone to fire, and is characterized by predominant and dense shrublands, extensive wildland-urban interfaces and relevant touristic pressure mostlyin summer. We first analyzedthe vulnerability to firesof about 13,000 housing units, and the closest neighboring (10-m buffer) combining aerial photographs and field surveys. About 40% of the housing units of the study area was classified as wildland-urban interface since it was in contact with the vegetation.Afterwards, we used simulation modeling based on the MTT algorithm of FlamMap (Finney 2006) to estimate fine scale fire exposure. For this analysis, we selected 32 different scenarios to represent the most common and critical conditions for fire occurrence and spread in the study area. For each scenario, we fixed 10,000 fire ignition points and we simulated the spread ofwildfires at a resolution of 20 m. We analyzed fire exposure profiles considering burn probability, flame length, fire size and source-sink ratio (SSR). We finally combined the WUI mapping and characterization results with the outputs obtained from the fire simulations, and we identified and quantified the level of risk of the housing units. As expected, the houses surrounded by shrublands and complex topography, particularly when isolated, showed very high fire exposure profiles and overall risk, while the lowest exposure was observed in compact villages and towns and in areas characterized by strategic fuel management.