Remapping California's wildland urban interface: A property-level time-space framework, 2000–2020

Abstract

Wildland fire poses a significant risk to property and people, and these risks tend to be highest in places where flammable, wildland vegetation abuts urban development. Traditionally, efforts to map these areas of intersection, known as the Wildland Urban Interface (WUI), have relied on satellite-derived land cover and census data. While these types of data are valuable for broadly delineating WUI areas, they are constrained in their ability to specifically identify at-risk residential properties and their characteristics over time. This article addresses these challenges through a multi-time-step, property-level framework that enhances current approaches based on moving window mapping, the Time Step Moving Window (TSMW) framework. We implement this framework on approximately 10 million geo-located property records from Zillow's Transaction and Assessment Database for California. Using this framework, we generate estimates of California's WUI from 2000 to 2020 and find that our time stepped building scale maps have allowed us to classify residential homes at-risk to burns with greater accuracy compared to time stepped Census polygon based maps. Based on these maps, we further estimate that approximately $1.34 Trillion, or 40%, of California's improved residential property value is situated within the WUI. Our approach provides a high-precision strategy for delineating at-risk residences and calculating localized financial costs associated with future hazard events.