California State Highway System Climate Change Vulnerability Assessment

As the hazards of climate change become more apparent on the west coast of the U.S., the need for more resilient infrastructure grows. In response to this need, the California Department of Transportation (Caltrans) engaged WSP USA to perform a statewide study to assess the vulnerability of highway system infrastructure in all 12 of its districts to various climate-related threats.

The approach WSP undertook to implement the study introduced unique technical processes tailored to California and its transportation engineering needs. The team evaluated future projections for five main climate hazards: temperature rise, wildfire, changes to precipitation, sea level rise and storm surge. They then identified areas along the highway that could be exposed to these stressors and considered how climate hazards may affect future highway design.

Though vulnerabilities varied by district, the study uncovered several trends that present a statewide concern. The data collection and evaluation effort WSP conducted for the study was the first and one of its kind to date.

Importantly, as WSP conducted research for the study, the approach to the effort was evolving. Originally, the objective was primarily the technical assessment and the data it would produce, but as wildfires and state climate policies drew increasing attention to climate adaptation, Caltrans became interested in developing additional reports accessible to government officials, regulatory agencies and the public.

In addition to the technical deliverables, WSP’s scope of work expanded to creating these highly visual and easy to understand summary reports for each individual district. The assessment data and summary reports are valuable tools all Caltrans districts can use during site evaluations or project planning to evaluate potential impacts.

WSP’s collaboration with Caltrans and their staff also led to the creation of the Caltrans Adaptation Strategy Report, which provides recommendations on how Caltrans can make climate change resiliency a core function and value of the agency and begin to adapt to climate change at a statewide level.

The vulnerability assessment and subsequent reports are the initial step to climate resiliency for California’s state highways, and in helping Caltrans, and its partners and stakeholders, understand how climate change could affect the highway system and the travelling public.