CalTrans Considers Alternatives to 'Armoring' 101 Against Sea Level Rise


As it faces flooding from sea level rise along the U.S. Highway 101 Arcata-Eureka, CalTrans is seriously considering a “living shoreline” instead of throwing riprap up against the tides. In a workshop yesterday, it also seemed clear the agency is going to keep the current road alignment at the edge of Humboldt Bay.

Clancy DeSmet, CalTrans' climate change adaptation branch chief, said planting a “natural shoreline” instead of “hard armoring” the highway might absorb or deflect rising waves. But because it’s never been tried and tested, the more natural alternative may not get state approval.

Relocating the entire highway inland is almost certainly off the table for consideration, said DeSmet, explaining it would be “cost-prohibitive” and entail moving communities.

CalTrans is seeking ways to keep 101 from drowning, and any suggestions are welcome between now and the spring, when the agency is set to have final reports on alternatives after analyzing roadway designs, geohazards and engineering. During the online workshop, about 65 participants, including Third District County Supervisor Mike Wilson and Eureka City Councilmember Kim Bergel, had plenty of questions, but no solution, to the problem of a major public thoroughfare facing a future of wetlands inundation.

A final plan for dealing with sea level rise on the corridor is due in December of 2025 — that is, unless the road starts flooding four times a year or more before then. Increased inundation would trigger an acceleration to the process, DeSmet noted.

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