Caltrans staff and WSP collaborated to analyze climate data from multiple sources, determine impact metrics specific to transportation program delivery, and develop reports that will represent an initial inventory of climate change-related effects statewide.

“Caltrans is the first department of transportation in the U.S. to comprehensively address the potential effects of climate change,” said Michael Flood, WSP’s project manager on this effort. “Caltrans staff is working to implement a risk-based framework for decisions, recognizing the true value of the transportation system to communities and the potential consequences to society of negative impacts.”

The Caltrans Climate Change Vulnerability Assessment Summary Report covers California’s District 4, focusing on concerns within the San Francisco Bay region. This is the first of 12 district reports WSP is developing that will identify how climate change may impact transportation assets across California.

As the project lead, WSP is responsible for coordinating with multiple research agencies and academic institutions to generate the data needed to guide decision-making for the transportation agencies. The firm also developed a series of specialized GIS routines to collect the required climate information and identify assets that may be exposed to climate risks. WSP staff then developed reports that present complex climate information in a way that is straightforward and easy to understand.

“There are risks out there that the agency needs to consider and incorporate into its investment programs,” Flood said. “These require engineering solutions to ensure the long-term viability of the system.”

This project was initiated following a recent increase in significant weather-related events that impacted California’s transportation system over the past few years. California legislation requires consideration of climate change for all state investments.

In 2015, heavy rains washed out a bridge on Interstate 10, impacting travel and goods movement on this critical roadway. In June 2017, a major landslide deposited tons of rock along Highway 1. And last December, dry weather conditions contributed to wildfires in both Northern and Southern California, which had a significant impact on travelers.

Near Santa Barbara, the loss of protective landcover due to wildfires resulted in a major mudslide during heavy rains that closed Highway 101 for weeks. In the last year alone, Caltrans incurred over $1.2 billion dollars in highway damage. The state also has over 840 miles of coastline that raise concerns about long-term coastal flooding and the impacts of climate change.

“This report provides Caltrans with its first inventory of assets that require additional consideration due to climate change,” Flood said. “It covers a broad set of stressors so that Caltrans can focus its efforts on maintaining the resiliency of the highway system to ensure it can withstand changing conditions, additional forces and long-term water levels as a part of new infrastructure design.”

While climate change studies typically focus on the impact of rising sea levels, this study also paid close attention to other factors, such as storm surge, precipitation change, temperature change, wildfires and coastal erosion/cliff retreat.

“Temperature change, for example, is important to consider when designing roadway pavement, to ensure that it remains viable for longer periods,” Flood said. “Precipitation change can impact how bridges and culverts are designed, and the potential for increased damage caused by flooding can be important to asset management considerations. Precipitation is also an important consideration in landslide risk.”

Caltrans is already taking proactive steps through a follow-up initiative, and WSP is providing consulting services to implement the findings of this report as a part of the agency’s transportation investments. The effort will include development of policies and actions to incorporate long-term risks into project development programs.

“Climate change poses an immediate and growing threat to California, and Caltrans is being proactive in determining what this means for the state's transportation system,” said Malcolm Dougherty, Caltrans’ recently retired director. “This study and those that will follow intend to provide data to support the discussion about how climate change impacts the way we plan, design, build, operate and maintain the state highway system."

The WSP team responsible for the project included Chris Dorney, Annika Ragsdale, Gregg Cornetski, Patrick Kresl, Don Hubbard, Mike Meyer, Jerry Ramsden, Tim Grose, Justin Lennon, Dan Turner and Ken Johnson. The same project delivery team that worked on the initial contract is working with Caltrans on the follow-up initiative, led by Hubbard.

“This was a fascinating project, totally out of the box and a first of its kind in the U.S. to put parameters around climate change impacts on transportation systems for multiple stressors,” Flood said. “Success in its delivery was heavily dependent on an integrated team that took on every challenge.”

The next transportation climate reports – for District 2 in Northeast California and District 6 in the Central Valley – are due to be released at the end of March. The entire effort is expected to be completed by mid-2019.