Mapping the WUI area in California based on remote sensing data

Abstract:

Due to the mixed distribution of buildings and vegetation, the wildland-urban interface (WUI) areas are characterized by complex fuel distributions and geographical environments. The behaviors of wildfires occurring in WUIs are significantly different from fires occurring only in wildland vegetation or building fires, often leading to more severe hazards. Therefore, WUI areas warrant more attention during the wildfire season. Currently, most of the widely used WUI maps were calculated and drawn based on the housing data in the decennial Census and the vegetation data from the National Land Cover Database (NLCD) updated every three to five years. In the context of the current increase in California’s population and housing, this update frequency and map resolution can no longer meet the firefighting frontline’s needs. However, the developments of remote sensing technology and data analysis algorithms have brought opportunities for improvement in WUI mapping. In this study, WUI was directly mapped with the building footprints in California extracted from satellite data by Microsoft along with the Normalized Difference Vegetation Index (NDVI) provided by MODIS based on maximum spot fire distance. This method did not require the calculation of housing density but designated the adjacent area of each building with large and dense areas of vegetation as WUI, which avoided the modifiable areal unit problem (MAUP). This method can not only refine the scope of the WUI area to each building, but also update the WUI map in real-time according to the update frequency of satellite data and operational needs. Therefore, this method is suitable for local governments to map exhaustive local WUI areas, formulating detailed wildfire emergency plans, evacuation routes, and management measures.