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 is sinking at the same rate the ocean is rising. According to the California Ocean Protection Council's 2018 projections, sea level in the Humboldt Bay area is expected to rise above 2000 sea level as much as 1 foot by 2030, 2 feet by 2050, and 3 feet by 2060. In late 2021, scientists reported that Antarctica's Thwaites Glacier is likely to collapse within 5 to 10 years, which could result in an additional 2 to 10.8 feet in sea level rise. The primary impacts from sea level rise are increases in flooding and erosion. Sea level rise will expand the area 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.

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

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.

But more work remains: 37 tons of nuclear waste are in an eroding bluff near King Salmon
Following a years-long effort to decommission the former nuclear power plant in Humboldt Bay, Pacific Gas and Electric Co. recently filed a request with the Nuclear Regulatory Commission to terminate the power plant’s license marking a “major milestone” for the Humboldt County community.
Decommissioning efforts for the Humboldt Bay Power Plant Unit 3, a 63-Megawatt electric boiling water reactor, began in June 2009, more than 30 years after the power plant had ceased operations. It operated from 1963 to 1976 and was permanently defueled in 1984.

As the world celebrates Earth Day 2021, local experts warn the historic Arcata dikes holding back Humboldt Bay will be overtopped monthly, possibly in as soon as 30 years, due to rising sea level from climate change. 
"There is no stopping sea level rise for the next century or next couple of centuries," said Aldaron Laird, an environmental planner specializing in local sea level rise who is currently working with Greenway Partners on several local projects. "It's just going to keep right on going."

Wiyot Tribe Natural Resource Specialist Adam Canter said Arcata has a site on McDaniel Slough that is at risk — one of 52 Indigenous cultural sites around Humboldt Bay that could be inundated in the coming decades.

Jennifer Kalt, director of Humboldt Baykeeper, identified three sites in Arcata that are at risk of tidal inundation in the coming decades that have tested positive for dioxin contamination: one on Janes Creek, another on Butchers Slough and the former Little Lakes Industries site off I Street near the Arcata Marsh and Wildlife Sanctuary. 
Last year the Arcata City Council voted to submit an application for a federal assessment grant of $300,000 for the same property and received the grant earlier this year.Last year the Arcata City Council voted to submit an application for a federal assessment grant of $300,000 for the same property and received the grant earlier this year.
Arcata Community Development Director David Loya said he is hopeful that the city will get the cleanup grant and the cleanup will begin as early as this fall, but he anticipates next summer is more likely.
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A new study on high tide flooding predicts that the mid-2030s could be catastrophically wet in U.S. coastal regions — and it could stay that way for an entire decade.

Led by members of the NASA Sea Level Change Team from the University of Hawaii, the study says that high tide flooding could happen more frequently on several U.S. coasts. Flooding at high tide, often called nuisance flooding, already occurs with regularity in many coastal communities as water routinely sloshes into streets, yards and businesses.

Two factors could converge to worsen flooding at high tide, the study says: rising sea levels fueled by climate change — and the moon.

The moon's orbit is due for its regular "wobble." That is entirely natural, NASA says, and it has been recorded as far back as 1728. Half of the moon's 18.6-year cycle creates lower high tides and higher low tides; the other creates higher high tides and even lower low tides.

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Aldaron Laird has been studying the effects of sea level rise on the Humboldt Bay for the past 10 years. He says that Humboldt Bay is experiencing the fastest rate of sea level rise on the West Coast because the bay sits on a tectonic plate that is being pulled down as the sea level rises. Laird told the Outpost that over the past 100 years or so the waters around the bay have risen around 12 to 18 inches. 

 

About 75 percent of the shoreline around the bay is artificially made, with a majority of it being earthen dikes from the late 1800s. Laird said there are 41 miles of dikes and that they are nearing a critical moment. 

 

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More Articles ...

  1. Fighting against the tide: King Salmon
  2. Humboldt's Climate Trouble: North Coast Perspectives
  3. Sea Level Rise is Here: Humboldt Baykeeper’s Jen Kalt on Podship Earth
  4. Radioactive: PG&E is storing six casks of nuclear waste near Humboldt Bay, raising concerns

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