CA - Humboldt County coastline sees fastest erosion rates in the state
Several of Humboldt County’s coastal cliffs rank among some of the fastest eroding bluffs in California, according to a recent study.
The cliffs on Centerville Beach and in the King Range ranked especially high on the list of California’s eroding coastal cliffs in the study, “Spatial and temporal trends in California coastal cliff retreat,” which found the Northern California coast is eroding at significantly higher speeds than the southern coastline.
The study noted that direct, quantitative relationships between cliff erosion and controlling factors are difficult to establish because of the inherent difficulty in measuring change in the rocks, especially since coastal erosion happens in spurts via landslides.
However, the environmental combination of sea level rise — a Humboldt County Civil Grand Jury released a report earlier this year detailing the effects of the projected three-foot rise in sea level — and climate change models which forecast hotter summers, but wetter winters, could further increase coastal erosion, Flanagan said.
Rising sea levels and increased coastal erosion leave communities with several options, said Gary Griggs, a professor of earth and planetary sciences who studies coastal erosion at the University of California, Santa Cruz. Communities can build sea walls — 13% of the coast has been armored with walls meant to break the tide — they can ignore the problem, they can truck in more sand on beaches, which he said was a short-term tactic, or they can engage in managed retreat, a strategy aimed at pulling back human structures from the coast.
Humboldt County’s cliffs could be eroding faster than others in the state because of many factors, including the local weather and the substance of the cliffs, said Sam Flanagan, a geologist with the Bureau of Land Management’s office in Arcata.
“We get big storms, big swells, lots of ocean energy at the base of the bluff, and then a lot of these bluffs, Centerville in particular, are really young marine sedimentary material. It’s roughly 3 to 7 million years old,” Flanagan said. “It’s old uplifted seafloor that really hasn’t been around long enough to turn into hard rock, so it’s basically just a big pile of loosely consolidated sand that’s perched above and in a very unstable configuration.”
However, while cliff erosion in Humboldt County presents some dangers, the hazards are not as prevalent as places like San Diego, where earlier this year, three people were killed after a portion of a cliff caved in, crushing the victims under tons of sandstone. Humboldt County’s relatively sparse population and general lack of expansive development on coastal cliff — much of the coast is reserved for recreation — mean that dangers present themselves in the form of crumbling cliffs under the feet of hikers who venture too close to the edge.