The SourceCivil Engineering MagazineCalifornia assesses the climate change vulnerabilities of its state highway system
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California assesses the climate change vulnerabilities of its state highway system

By Jay Landers

After examining each of its 12 districts in terms of their vulnerabilities to climate change, the California Department of Transportation is looking to integrate the findings into its long-range efforts to address the anticipated effects of extreme weather on its state highway system. In July, Caltrans announced it had wrapped up the Climate Change Vulnerability Assessment Reports for District 1 (Eureka) and District 5 (San Luis Obispo/Santa Barbara). The reports concluded the department’s work to assess climate change vulnerabilities within its districts. 

Each report includes a high-level summary of potential effects from climate change on each district’s portion of the state highway system and a technical report detailing the processes used to identify the effects. In general, the reports examine how the districts will likely be affected in the future by rising average temperatures, higher sea levels, storm surge, and precipitation. These effects “increase the incidence of flooding, drought, wildfires, coastal erosion, and mudslides,” Caltrans said in a July 15 news release. “Understanding these impacts helps Caltrans assess physical climate risk to the transportation system and work towards adapting our infrastructure to be more resilient to these impacts.”

In some cases, climate change is expected to have stark consequences for California’s state highway system. For example, sea levels along the state’s coast are anticipated to rise by 5.5 ft by 2085, accelerating soil erosion and cliff retreat along 130 mi of state highway. More than 7,000 mi of state highway face a greater risk associated with the increased severity and frequency of wildfires. Such threats are particularly acute along the central coast and northwest part of California, where high temperatures could rise by 6 to 12 degrees, increasing the potential for drought and wildfires. These reports are timely in light of the state’s recent record-setting heat and raging wildfires, which had burned some 2 million acres as of press time. 

“The completed assessments cover all 58 counties in the state and give California a comprehensive evaluation of climate change effects” on the state highway system, according to the release from Caltrans. “We are now integrating the findings into our planning process to better protect California’s citizens, economy, and transportation investments.” To this end, Caltrans is developing a “comprehensive database” that it will use to evaluate, mitigate, and adapt to the effects of increasing extreme weather events on the state’s transportation system, according to the department’s news release.

The vulnerability assessments “help inform long-range planning documents, programming documents, environmental documents, and the permit application analyses with respect to sea-level rise and how we might potentially respond to those impacts,” says Christopher Clark, a media relations manager for the department. Such assessments also “help inform the creation of more robust corridor plans,” he notes. “The reports will assist in identifying at-risk assets, prioritize exposed assets, and explore adaptation solutions.” 

Data compiled during the creation of the district reports are hosted in an interactive map prepared using the ArcGIS Online mapping service provided by Esri. Individual districts also can use the geospatial mapping tool “to cross reference with regional maps in order to better identify the areas that frequently require emergency intervention,” Clark notes.

Caltrans is working to develop estimates of the potential costs to address the vulnerabilities identified in the reports. “Two pilot facility-level projects are currently underway that will provide a framework for districts on how to address the severity of potential climate change impacts and perform economic analyses to determine which effort would be the most cost-effective over the long term,” Clark says. The department also is developing an estimate of the cost per mile to adapt the state highway system to sea-level rise.

This article first appeared in the October 2020 issue of Civil Engineering.

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