Evaluating rural Pacific Northwest towns for wildfire evacuation vulnerability

Project Description

Wildfire is an annual threat for many rural communities in the Pacific Northwest region of the United States. In some severe events, communities are ordered to evacuate as wildfire advances. Since most people evacuate in personal vehicles, the quality of the surrounding road network is a critical component of a community's vulnerability to wildfire. This study leveraged a high-resolution spatial dataset of wildfire burn probability and mean fireline intensity to conduct a regional-scale screening of wildfire evacuation vulnerability for 696 rural towns in Oregon and Washington.

Purpose and Scope

This study focused only on towns in Oregon and Washington that are designated as “rural” by the U.S. Census. It was intended to stimulate further refinements and innovations in evaluating community wildfire evacuation at the regional scale.

Methods

The scientists characterized each town’s surrounding road network to construct four simple road metrics related to the potential to quickly and safely evacuate—connectivity, travel area, directionality, and number of “exits.” They then combined the road metrics with fireline intensity and burn probability—two metrics characterizing fire hazard of the surrounding landscape through which evacuation will occur. By combining the road and fire metrics, they created a composite score for ranking all towns by their overall evacuation vulnerability.

Key Findings

• In this study, overall evacuation vulnerability was highest in towns where the poorest road networks coincided with the highest wildfire hazard. Often, these towns were located in remote, forested, mountainous terrain, where topographic relief constrained the available road network and high fuel loads increased wildfire hazard.
• Towns with the highest overall vulnerability in this study were located primarily along the west and east sides of the Cascade crest, northeastern Washington, southwestern Oregon, and Oregon’s Blue Mountains.
• A low vulnerability ranking by no means indicates that a town does not have fire hazard, nor that a town’s road network will sufficiently facilitate evacuation of all residents. None of the towns analyzed had zero fire hazard. Towns with objectively low vulnerability can still experience extreme, high-danger wildfire events.
• Assessing evacuation vulnerability is complicated and requires many approaches. This study is not the final, definitive doctrine about evacuation vulnerability in these rural towns; it is a starting point to stimulate further refinements and innovations in evaluating community wildfire evacuation at the regional scale.

Project Deliverables

July 29, 2021 webinar. In this hour-long webinar, scientists Alex Dye and John Kim highlight the findings of their study.

Wildfire evacuation risk for PNW communities interactive study map