Coastal infrastructureSea level rise threatens California coastal infrastructure

Officials in Humboldt County, California are preparing for sea level rise, which experts say could threaten utilities and U.S. highway 101. The National Research Council warns that California, Oregon, and Washington could experience twelve inches of sea level rise by 2050 and thirty-six inches by 2100.

Environmental planner Aldaron Laird of Trinity Associates believes that even those predictions are conservative. “All of the observations of actual tide changes and sea level changes have been higher and greater than what the models have shown we should expect,” he said. Laird completed a walkthrough inventory and mapping project of the 102-mile shoreline of Humboldt Bay, in which he discovered that between 1890 and 1910, roughly 30 percent of the bay was diked off and reclaimed for agriculture. Laird believes that even without taking sea level rise into account, the forty-one miles of dikes will eventually fall apart due to lack of maintenance. “It’s like what we saw a couple of weeks ago at the wildlife refuge when a dike breached: all of a sudden fifty acres were flooded overnight,” he continued. “If the dikes on Humboldt Bay fail, the bay is going to expand by 50 percent.” Laird blames the region for failing to maintain the artificial shoreline built over a century ago, and then building critical utility lines on the lands.

According to the project funded by the Coastal Conservancy, sea level on Humboldt Bay has increased by eighteen inches over the past century due to increasing tide elevation and subsidence — “the gradual caving in or sinking of land.” Gas, electrical, and water transmission lines are all buried in the farmlands behind dikes that fortify the shoreline. “All these underground utilities weren’t designed to be saturated by saltwater, and we won’t be able to get out there to maintain them if those areas become part of the bay again. Same thing with Highway 101. They built 101 over these low-lying areas, and over the last century a lot of that land has been compacted by as much as 3 feet. So that’s where our vulnerability lies,” Laird said.

The Times-Standard reports that an Adaptation Planning Working Group, which includes staff members from more than a dozen local and federal agencies, is examining regional adaptation strategies to address the effects of sea level rise on the Humboldt Bay region. Hank Seemann, deputy director of Environmental Services for the Humboldt County Public Works Department said the group will release its report to the community mid-November. “For sea level rise, we’re dealing with a scale that’s an order of magnitude bigger than we’re accustomed to dealing with in terms of the extent of the natural hazard and the scope and cost of potential adaptation measures,” Seemann said. “We’re entering a new age in terms of understanding and responding to sea level rise, and part of the planning group’s role has been to get all the jurisdictions together to discuss options. The infrastructure all connects, and things are connected hydraulically, so we need to look at this from a regional perspective. We need a consistent, orchestrated approach so we can incorporate sea level rise into normal capital improvement planning, which is already beginning to take place.”