Assessing fire risk in the wildland-urban interface

Identifying areas of the wildland-urban interface (WUI) that are prone to severe wildfire is an important step in prioritizing fire prevention and preparedness projects. Our objective is to determine at a regional scale the relative risk of severe wildfire in WUI areas and the numbers of people and houses in high-risk areas. For a study area in northern lower Michigan, we first develop a spatial database of WUI areas (both intermix and interface) using housing data from the 2000 US Census and 1994 vegetation data from the Gap Analysis Project of the Michigan Department of Natural Resources. Then, we develop a spatial database of historic (pre-1900) fire regimes and current (1994) fuels to identify areas with high risk of stand-replacing fires. High-risk areas historically supported jack pine (P. banksiana Lamb.) and mixed pine forests with stand-replacing fire rotations less than 100 years and currently support upland conifer and hardwood forests. Analysis of the databases shows that 26% of the study area is WUI. About 25% of the WUI has relatively high fire risk. Over 88% of the WUI with high fire risk has low housing density (<1 house per 2 ha) and is classified as intermix where fuels and structures intermingle. The predominance of high-risk intermix areas with low-density housing has implications for planning effective fuel treatments and evacuation plans.