A RETRO-ANALYSIS OF THE JANUARY 7TH, 2022 FLOOD CLOSURE OF I-5

Abstract

Floods pose an acute risk to transportation networks and impose large costs on travelers. A twenty-mile section of Interstate 5 (I-5) was forced to close on January 7th, 2022, when rising floodwaters from the Chehalis, Skookumchuck, and Newaukum Rivers threatened to cover the highway. Many travelers and residents were unable to reach their destinations and alternate routes quickly became congested. This retroactive analysis investigated the total cost of the flood closure using traffic counts from permanent traffic recording stations, AAA’s estimated cost per mile of operating a vehicle for 2021, and the standard velocity equation—time equals distance divided by velocity—to solve for time cost. Through a GIS-based network analysis, two unique alternative routes are identified and time and mileage costs for travelers are calculated. Route One costs $151.97 while Route Two costs $160.67 in time per vehicle. Respectively, the routes cost $103.65 and $114.20 in mileage costs for each vehicle. Additionally, two historic Washington State Department of Transportation (WSDOT) detour routes are compared in time and mileage costs. Historic Route One costs $266.10 in mileage and $703.94 in time. Historic Route Two is much more expensive at $338.10 in mileage and $1,136.47 in time. The total cost of the flood closure was $924,950. With only one direct route to access so many destinations, it continues to be vitally important to increase access to urban and rural destinations during flood disasters.