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Study Evaluates Hwy 101 as Climate Change Closes In

The authors of a new study on the vulnerability of road infrastructure to climate change say impacts will happen more quickly than anticipated and need to planned for now.

A final version of the study was presented in a public meeting held on Dec. 18 at Eureka City Hall. The vulnerability analysis is one of 16 being done statewide, substantially funded by the Federal Highway Administration.

The work reflects a new approach to studying climate change. “A lot of the work, historically, has really been past-looking – what’s happening behind us,” said Rebecca Crow of the Eureka-based GHD engineering firm, which helmed the study. “We’re really at a changing point in time in how we look at and evaluate data and we’re starting to look forward, to project what the climate will be in the future.”

One of the study’s main objectives is to assess the vulnerability of California Department of Transportation (Caltrans) infrastructure in the district made up of Humboldt, Del Norte, Mendocino and Lake counties.

Another goal is developing “adaptation options” such as re-routing roadways, armoring them or constructing causeways that allow water to pass beneath them. Criteria for ranking the options range from cost considerations to social and environmental impacts.

The options and criteria were voted on by those who attended a public hearing in Eureka last August. In Humboldt, the Highway 101 safety corridor between Arcata and Eureka is the most at-risk piece of road infrastructure and armoring it, building causeways and re-routing it were ranked highest by attendees of the previous meeting.

Crow described climate change as a current phenomenon. “There are existing extreme weather events that tell us that things are changing and we’ve got to start taking notice,” she said.

As an example, she showed photos of a 9.1-foot early December king tide that almost completely submerged Indian Island. Other photos showed the effects of increasingly frequent flooding in Mendocino and Del Norte counties.

“This is a serious issue, we’re starting to see it now and we anticipate things to get worse in the future,” said Crow.

The study includes impact modeling based projections to 2050 and 2100. Brett Vivyan of GHD said the study’s projection of annual average daily temperatures by 2050 shows a rise of about three degrees in the region.

By 2100, the temperature increase is estimated at between four and six degrees.

Sea level rise is also modeled in the study and is an acute concern for Humboldt Bay, where land is subsiding. Under a high emissions or worst case scenario, the study projects sea level rise of between 10 to 26 inches in the Highway 101 safety corridor area by 2050 and between 26 to 70 inches by 2100.

Extreme precipitation is projected to increase by up to 11 percent by 2050 and up to 14 percent by 2100.

The bay is ringed with levees but “as seas get higher than those levees, there’s more room for the sea to move in,” said Vivyan.

Other areas of the county are prone to coastal flooding and rain-driven landslides, he continued. But the Highway 101 safety corridor is particularly vulnerable to rising seas and has high impact potential due to its traffic volume.

Crow said the next steps include aligning Caltrans design standards with anticipated changes. “If Caltrans continues to design for the status quo, there’s little room for adaptation,” she continued.

Questions were fielded from the audience, which included residents of other counties linked to the event via webinar technology. In response to a query about changing projections, Crow said the study includes a range of models which will be continually re-evaluated.

“This is a newer type of science that we’re doing,” she continued.

The study’s website is at

One Comment

  1. Jim Updegraff December 31, 2014

    The big question is whether the DOT is up to meeting this climate change impact on Highways. When you look the Willits By-pass fiasco and the critical problems with the Bay Bridge one has to say NO they are not. It will be one more failure by DOT.

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