Sea Level Rise

The Humboldt Bay area is experiencing the fastest rate of relative sea level rise on the West Coast. That's because tectonic activity is causing the ground beneath the bay to sink at the same rate that the ocean is rising. According to the California Ocean Protection Council's 2024 Science & Policy Update, sea level in the Humboldt Bay area is expected to rise approximately 1.5-2 feet above 2000 levels by 2060 and 3.9-5.5 feet by 2100. 
The primary impacts from sea level rise are increases in flooding, erosion, and rising groundwater. Sea level rise will expand areas vulnerable to flooding during major storms, as well as in the rare but catastrophic event of a major tsunami. The term 100-year flood is used as a standard for planning, insurance, and environmental analysis. But these extreme storms are happening with increasing frequency, in part due to rising seas. Sea level rise will cause more frequent—and more damaging—floods to those already at risk and will increase the size of the coastal floodplain, placing new areas at risk to flooding.
To view sea level rise scenarios for the Humboldt Bay area, visit NOAA's 2022 Sea Level Rise Viewer and go to the local scenario for the North Spit.     

Interactive Map of King Tide Photos

The California Coastal Commission's King Tide Photo Project features photos from the Humboldt Bay area and across the state. Anyone can upload photos online or via a smartphone app. Click HERE to upload yours.
Wondering about good spots to view the King Tides around Humboldt Bay? Visit our Humboldt Bay King Tide Photo Project.

Left: Erosion along New Navy Base Road in Samoa during the December 23-24, 2022 King Tides. Photo by Jen Kalt.

Forty-four feet isn't all that high. It's halfway up the tall side of the county courthouse. If you stacked Guy Fieri seven-and-a-half times on top of himself, his platinum blond hair would reach 44 feet high. Forty-four feet is also the height above today's sea level where 37 tons of radioactive waste from the former PG&E Humboldt Bay power plant is entombed in a concrete vault at the edge of the bay. A new coalition called, you guessed it, 44 Feet has brought together state agencies, federal and local political interests, scientists, a few folks with no titles at all and, to some extent, the nuclear plant's owner, PG&E. Like nanoplastics and deep-fried butter, most of us do not want to think about radioactive waste stored nearby, but 44 Feet is trying to plan for its future safety, even if that future is 100,000 years away.
PG&E's old nuclear power plant sat next to U.S. Highway 101 at King Salmon. It ran a brief and ignominiously leaky life from 1963 to 1976. Still, it produced high-level radioactive waste from the uranium fuel it used to create electricity. The radioactivity has cooled somewhat in the intervening years, but it will remain hot and toxic for more than 100,000 years.
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The Humboldt County Grand Jury's report is an excellent overview of how sea level rise will impact the Humboldt Bay Area. In plain language that's easy to understand, the report discusses the current understanding of the problems our region will face in the coming decades. It also identifies obstacles to "adaptation planning," or how we will adapt to lessen the impacts on people, highways, sewer plants and pipelines, electrical transmission and water lines, low-lying contaminated sites, etc. We need to start planning now so we can take action before these situations become emergencies, putting public health, safety, and the environment at risk.

Below are some excerpts:

Most people think of SLR as a problem when barriers get overtopped. They often overlook inundation that occurs when water seeps through the barriers. Few realize that even with well-maintained barriers, sea water will permeate through the barriers and intrude into the ground water on the other side. This process is known as salt water intrusion and must be considered when protecting our threatened areas.

The Grand Jury believes SLR planning needs to be a priority among all elected officials in the County. The County of Humboldt; the cities of Arcata and Eureka; and the Humboldt Bay Harbor, Recreation, and Conservation District should formally state their immediate and continuous support for, and commitment to, SLR mitigation and adaptation efforts. 

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Three feet of sea-level rise would have significant impacts to communities surrounding Humboldt Bay, but that’s exactly what’s expected to happen in the coming decades.
That’s why the Humboldt County Civil Grand Jury’s second report “The Sea Also Rises,” issued Thursday, states that Humboldt County, the cities of Arcata and Eureka, the Humboldt Bay Harbor, Recreation and Conservation District, and state legislators need to start collaborating on planning for sea-level rise.
“A regional voice speaks louder than multiple local voices,” the report states.
Some of those efforts are at the beginning stages. Humboldt County’s Planning and Building Department, for instance, is expected to conclude the Humboldt Bay Sea Level Rise Regional Planning Feasibility Study in September 2022 and that will likely recommend taking a collaborative approach to the issue.
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Scientists, speaking at the American Geophysical Union Fall Meeting in New Orleans this month, reported that a critical section of the keystone Antarctic glacier, Thwaites Glacier, will likely collapse in the next five to ten years. The research, led by Erin Pettit of Oregon State University, predicts that the Thwaites ice shelf will break apart within the next decade because of startling increases in surface fractures and rifts.
Thwaites Glacier is one the largest Antarctic glaciers, comparable to the size of Great Britain or Florida. Meltwater from Thwaites alone is responsible for 4% of global sea level rise, leading it to receive a great deal of scientific attention in recent years.
The nickname ‘Antarctica’s doomsday glacier’ is given to Thwaites because if the ice shelf collapses, the glacier and the enormous volumes of ice upstream that funnel into the glacier will no longer be restrained from accelerating into the ocean. “It is the potential long-term effect on the rest of the grounded ice sheet that we need to consider,” explains Anne Le Brocq, a senior lecturer in physical geography at the University of Exeter. If the entire glacier were to melt then global sea levels would rise by 65 centimeters, or about two feet. If Thwaites Glacier, and other critical neighboring glaciers such as Pine Island Glacier, cannot hold back the West Antarctic Ice Sheet, which holds the equivalent of 3.3 meters (10.8 feet) in sea level, then it could affect coastlines across the world.
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Anyone who has ever driven south on U.S. Highway 101 between Arcata and Eureka during a storm at high tide can't help but notice how close the water comes to the highway. Sea level rise, which scientists assure us is now inevitable, will only make things worse. The only questions are how much worse and when. If and when the ocean covers the 101 corridor between Eureka and Arcata, nobody will be able to say the issue hadn't been on Caltrans' radar. Whether the agency will have actually done anything, however, remains to be seen.
Aldaron Laird of Trinity Associates says the Ocean Protection Council's 2018 sea level rise projections indicate planners should expect the waters along the U.S. Highway 101 safety corridor to rise a foot by 2030, 1.6 feet by 2040, 2.3 feet by 2050 and 3.1 feet by 2060. Some believe those projections are already outdated. The lowest point on the southbound lane of U.S. Highway 101, meanwhile, sits about 2 feet above peak high tide levels.

More Articles …

  1. PG&E completes decommissioning process, ends nuclear facility license
  2. A Study Predicts Record Flooding in the 2030s, and it's Partly Because of the Moon
  3. Arcata Under Pressure: Local leaders contemplate sea level rise and its looming local impacts 
  4. As the Planet Heats Up, The County Plans to Address Rising Sea Levels With an Emissions Reduction Plan and a Slow Retreat Strategy

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