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.

Supervisors back study of rising sea; Bay infrastructure threatened

10/10/12

The county is looking at ways to protect coastal communities on Humboldt Bay threatened by rising sea levels and aging dikes. The Board of Supervisors on Tuesday voted unanimously to support a recent application for a $250,000 Coastal Conservancy grant that would allow nonprofit Coastal Ecosystems Institute of Northern California to adapt planning and technical studies associated with sea level rise in Humboldt Bay.

Aldaron Laird of Trinity Associates said at Tuesday’s meeting that the first phase of the project — the first comprehensive mapping of Humboldt Bay, funded by the Coastal Conservancy — was complete. Seventy-five percent of Humboldt Bay’s 102 mile shoreline is artificial, Laird said, meaning it needs maintenance.

Laird said Humboldt Bay has the highest rate of sea level rise on the West Coast and showed examples of crumbling dikes and shoreline areas that already flood yearly.

Harbor district Director of Conservation Division Dan Berman said it was an important issue for the district, adding that even if sea level rise goes more slowly than expected, it’s already a problem on the bay.

Rising Seas Pose Risks Around Humboldt Bay

Thousands of acres of former tidal wetlands currently at or below sea level around Humboldt Bay—including most of Manila, Samoa, Fairhaven, some residential and commercial areas of Eureka and Arcata, and many agricultural lands near the bay—are at risk of increased flooding in the coming years. 

Rising sea levels around Humboldt Bay

  Aldaron Laird, who walked or kayaked all 102 miles of Humboldt Bay’s shoreline and its sloughs as part of his study, “Humboldt Bay Shoreline Inventory, Mapping and Sea Level Rise Assessment,” was the featured speaker on May 30 at the Arcata Marsh Interpretive Center.

Laird is an environmental planner who specializes in getting permits for wetland enhancement projects and doing historical studies of rivers and tidal waters. He produced the Humboldt Bay Historical Atlas in 2007.  

This year, Laird is completing work for a California Coastal Conservancy grant to inventory the bay’s shoreline and “ground truth” GIS data on the shoreline’s attributes — part of a statewide effort to map areas that will be affected by sea level rise.   During his tour of the bay's shoreline, Laird discovered that acres of diked farmland are currently ill-equipped to hold back the rising sea. The last native salt marsh ecosystems are also at risk of being drowned out by sea level rise.   Laird’s presentation will include some of his 14,000 photographs taken during the project.

To watch online, click HERE. Thanks to Access Humboldt!

For more info, see "Aldaron's Walkabout" in January's North Coast Journal.

California faces more serious risk of sea level rise than other areas

6/22/12

As the world continues to warm from climate change, most of California -- including San Francisco Bay -- will see a greater rise in sea level than other parts of the planet, according to a prominent national study released Friday.

The report, from the National Academy of Sciences, found that the impacts of melting ice and warming, expanding oceans will hit California harder because most of the state's coastline is slowly sinking due to geological forces.

Ocean levels south of Humboldt County will rise up to 1 foot in the next 20 years, 2 feet by 2050, and up to 5 feet by 2100, the study showed.

Rising Sea Levels Seen as Threat to Coastal U.S.

3/13/12

About 3.7 million Americans live within a few feet of high tide and risk being hit by more frequent coastal flooding in coming decades because of the sea level rise caused by global warming, according to new research.

If the pace of the rise accelerates as much as expected, researchers found, coastal flooding at levels that were once exceedingly rare could become an every-few-years occurrence by the middle of this century.