From: Rhea Varley
To: Beth Redfern
Subject: FW: OLD BUSINESS Initiate Adoption of the Comprehensive Update to the City’s Local Coastal Program Date: Tuesday, March 3, 2026 10:35:12 AM
For Blue Folder.
From: Gregory Daggett < >
Sent: Tuesday, March 3, 2026 10:22 AM
To: Meredith Matthews <[email protected]>; Stacy Atkins-Salazar <[email protected]>; Alex Stillman <[email protected]>; Kimberley White <[email protected]>; Sarah Schaefer <[email protected]>; Tabatha Miller <[email protected]>; David Loya <[email protected]>; Rhea Varley <[email protected]>; Merritt Perry <[email protected]>; Engineering Dept <[email protected]>; Emily Sinkhorn <[email protected]>; Jennifer Dart <[email protected]>; Delo Freitas <[email protected]> Subject: OLD BUSINESS Initiate Adoption of the Comprehensive Update to the City’s Local Coastal Program
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Re: Critical Fire‑Safety and Rapid‑Subsidence Hazards in the Comprehensive LCP Update
Dear Mayor and Council members and City Leadership Team, As you initiate adoption of the Comprehensive Update to Arcata’s Local Coastal Program (LCP) on March 4, 2026, I urge you to address two major public‑safety risks that remain insufficiently integrated into the current draft: (1) the Arcata Fire Protection District’s clearly stated inability to safely serve buildings taller than three stories, and (2) the scientifically documented threat of rapid land subsidence during a Cascadia megathrust earthquake, which would instantly expand coastal flood exposure far beyond gradual sea‑level‑rise projections.
Fire Protection Limitations and the January 2, 2026 Downtown Fire Arcata Fire Protection District (AFPD) has stated repeatedly, in writing and on multiple occasions, that it cannot provide adequate fire or emergency response for structures exceeding three stories. This is not a theoretical concern. On January 2, 2026, when a major fire broke out in the City of Arcata, the incident required all available firefighters and equipment in Humboldt County. Even with countywide mutual aid, the event strained capacity to its limits.
This real‑world demonstration underscores AFPD’s warnings: Arcata does not currently possess the staffing, ladder‑truck capability, or operational redundancy to safely protect taller structures. Any LCP update that contemplates increased height limits, intensified development, or denser coastal‑zone housing must explicitly reconcile these constraints. Failing to do so places residents, first responders, and the City itself at unacceptable risk.
Cascadia Megathrust Earthquake: Rapid Subsidence and Instant Coastal Inundation The April 30, 2025 Los Angeles Times article by Rong‑Gong Lin reported that a Cascadia “monster” earthquake could cause rapid land subsidence of several feet, transforming today’s coastal margins into suddenly inundated zones. Unlike gradual sea‑level rise, this hazard would occur within minutes, creating long‑lasting flooding and severely complicating evacuation, emergency response, and post‑disaster recovery.
Arcata’s LCP update and related grant‑funded vulnerability assessments do address sea‑level rise, tides, waves, and stormwater hydraulics. However, the current materials emphasize progressive inundation scenarios, not the instant, earthquake‑triggered subsidence that leading geoscientists warn is both plausible and historically documented along the Cascadia Subduction Zone.
This gap is consequential. Rapid subsidence would:
• Expand the floodplain far beyond current projections. • Render some evacuation routes impassable within minutes. • Increase the duration and depth of coastal flooding for months or years. • Compound fire‑response challenges, especially if infrastructure is damaged simultaneously.
An LCP that does not explicitly incorporate this hazard leaves Arcata underprepared for the most catastrophic—but scientifically credible—scenario our region faces.
Request for Council Action
As you move toward adoption of the updated LCP, I respectfully request that the Council:
• Integrate AFPD’s documented three‑story service limitation into all land‑use, zoning, and coastal‑development standards.
• Require hazard‑mitigation policies that address rapid subsidence, not only gradual sea‑level rise.
• Reevaluate coastal‑zone development intensity in light of both fire‑response constraints and Cascadia‑related inundation risks.
• Ensure that emergency‑access, evacuation, and infrastructure‑resilience planning reflect the combined impacts of fire, earthquake, and sudden coastal flooding.
Arcata’s LCP is one of the City’s most powerful tools for long‑term safety and resilience.
Incorporating these realities now—before new development patterns are locked in—will protect lives, safeguard public resources, and ensure that Arcata’s coastal future is planned with full awareness of the hazards we face.
Sincerely,
Gregory Daggett
CALIFORNIA COASTAL ACT
Chapter 3 - COASTAL RESOURCES PLANNING AND MANAGEMENT
POLICIES
Article 8 – Sea Level Rise
Section 30270 - Consideration of the effects of sea level rise The commission shall take into account the effects of sea level rise in coastal resources planning and management policies and activities in order to identify, assess, and, to the extent feasible, avoid and mitigate the adverse effects of sea level rise.
Ca. Pub. Res. Code § 30270
Added by Stats 2021 ch 236 (SB 1),s 2, eff. 1/1/2022.
The Coastal Act Laws and Regulation Chapter 3-Coastal Resources Planning and Management Policies Article 6 30251 states
The scenic and visual qualities of coastal areas shall be considered and protected as a resource of public importance. Permitted development shall be sited and designed to protect views to and along the ocean and scenic coastal areas, to minimize the alteration of natural land forms, to be visually compatible with the character of surrounding areas, and, where feasible, to restore and enhance visual quality in visually degraded areas. New development in highly scenic areas such as those designated in the California Coastline Preservation and Recreation Plan prepared by the Department of Parks and Recreation and by local government shall be subordinate to the character of its setting.
(Added by Stats. 1976, Ch. 1330.)
Monster earthquake could sink swath of
California, dramatically heightening flood risk,
study says
By Rong-Gong Lin IIStaff Writer
April 30, 2025 4 AM P
During an earthquake scenario with the highest level of subsidence, or land sink, the area at risk of flooding would expand by 116 square miles.
Among the areas at risk after a megaquake along the Cascadia subduction zone are the Humboldt Bay region, including the area around Eureka and Arcata.
A long-feared monster earthquake off California, Oregon and Washington could cause some coastal areas to sink by more than 6 feet, dramatically heightening the risk of flooding and radically reshaping the region with little to no warning.
Those are the findings of a new study that examined the repercussions of a massive earthquake on the Cascadia subduction zone, which stretches from Northern California up to Canada’s Vancouver Island.
The study, published Monday in the journal Proceedings of the National Academy of Sciences, concluded that in an earthquake scenario with the highest level of subsidence, or land sink, the area at risk of flooding would expand by 116 square miles, a swath that’s 2½ times the size of San Francisco.
Such a scenario would more than double “the flooding exposure of residents, structures and roads,” and officials would need to contend with a future of “compromised roadways and bridges,” as well as lifelines and infrastructure that are either more frequently flooded or permanently inundated, the study’s authors wrote.
In other words, a powerful earthquake in this area would risk “drastically altering shorelines and causing profound, lasting impacts to coastal populations, infrastructure, and ecosystems,” the study said. Unlike relative sea-level rise that’s driven more gradually by climate change, a rise resulting from a major earthquake “will happen within minutes, leaving no time for adaptation or mitigation.”
The last megaquake on the Cascadia subduction zone, registering a magnitude 9, occurred in 1700. Based on archaeological evidence, villages sank and had to be abandoned, according to the U.S. Geological Survey.
From California’s North Coast to Washington state, scientists say, the next great earthquake — magnitude 8 or higher — could cause land to sink by 1.6 to 6.6 feet, the same range seen during the 1700 earthquake.
Currently, more than 8,000 people live in flood plain areas along estuaries in the Cascadia coastal region. But in the event of a high level of subsidence after an earthquake, that figure would nearly triple to more than 22,000, the study calculates.
Nearly 36,000 structures would be threatened by the resulting quakeinfluenced flood plain, a 168% increase from the current figure of about 13,000.
And an additional 777 miles of roadway would be in the new flood plain, nearly tripling the at-risk total to 1,212 miles of road.
The flood plain is defined as areas that have at least a 1% chance of flooding each year, which is considered to be “high risk,” according to the Federal Emergency Management Agency. These are areas that have at least a 1-in-4 chance of flooding during a 30-year mortgage. Flood insurance must be purchased by home and business owners in high-risk areas with mortgages from federally regulated or insured lenders.
Radiocarbon dating suggests there have been more than 11 great earthquakes off the shore of California’s North Coast, Oregon and Washington state over the last 6,000 to 7,000 years — recurring every 200 to 800 years, the study said.
“Gradual climate-driven sea-level rise is not the only inundation threat,” the study said. “Coastal subsidence from the next great [Cascadia subduction zone] earthquake may produce” more than 3 feet of sudden relative sea-level rise sooner than otherwise expected.
When discussing a future megaquake on the Cascadia subduction zone, “We often hear about the tsunami and the shaking. But there’s the subsidence that’s going to persist — for decades to centuries —after the earthquake, and just totally alter the flood plains,” Tina Dura, assistant professor of geosciences at Virginia Tech and the study’s lead author, said in an interview.
One estimate published by FEMA is that a magnitude 9 earthquake along the full length of the 800-mile fault zone would leave 5,800 dead from the earthquake alone. An additional 8,000 would die from the resulting tsunami that could rise as high as 80 feet and offer coastal areas as few as 10 minutes of warning. Total economic losses could hit $134 billion.
In the 1700 Cascadia megaquake, oral histories describe tsunamis more than 50 feet high wiping out coastal villages. In Anacla, a village on what is now called Vancouver Island, only 1 out of more than 600 people survived, according to the U.S. Geological Survey.
The tsunami was so strong that it uprooted trees. When it finally receded, treetops were found strewn with trash and victims’ limbs. “Ghost forests” of rot-resistant trees found in tidal marshes and estuaries in the region are evidence that land sank during the quake and drowned the trees, the USGS said.
The results of the latest study should be a wake-up call to residents and government officials considering a postquake response, scientists say. There already are parts of U.S. Route 101 that routinely flood during exceptionally high king tides, Dura said, “and places like that could be kind of a hot spot for seeing flooding right away after the subsidence” following a megaearthquake.
Another factor officials should consider is whether crucial infrastructure, such as airports, would fall within the quake-expanded flood plain, scientists say.
A Major Cascadia Zone
Humboldt and Arcata Bay during a 2021 king tide. | File photo by Tim Hanan.
Earthquake Could Cause Much
of Coastal Humboldt to
Rapidly Drop Into the Sea,
New Study Finds
ESPAÑOL
###
Those of us who live in earthquake country tend to have two primary anxieties about the unsettling events: the shaking itself (collapsed roofs, crumbling buildings, etc.) and a tsunami (giant wall of water, ‘nuf said). However, a newly published study invites us to adopt an altogether new earthquake-related fear: rapidly sinking land.
The study, published Monday in the Proceedings of the National Academy of Sciences (PNAS), found that a major earthquake along the Cascadia subduction zone will likely cause between 1.6 and 6.5 feet of sudden subsidence long the Washington, Oregon and northern California coasts.
This abrupt land sinkage would dramatically raise the relative sea level of coastal communities in a matter of seconds. In the worst-case scenario, the subsidence would more than double the flooding exposure of coastal residents, structures and roads. And those risks would remain long after the shaking settles.
Floodplain map and bar graph depicting the expansion of the 1% floodplain (an area with a 1-in-100 chance of flooding each year) after earthquake-driven subsidence today (2023) and in 2100 when the earthquake-driven subsidence is amplified by climatedriven sea-level rise for Humboldt Bay. The bar graph shows the amount of land area, number of residents, structures, roads, and different land-use types in the 1% floodplain following earthquakedriven subsidence today (2023) and in 2100, when the effects of “This lesser talked about hazard is going to persist for decades or centuries after the earthquake,” the study’s lead author, Dr. Tina Dura, told NBC News. “The tsunami will come in and wash away and it’s going to have big impacts, don’t get me wrong, but the lasting change of the frequency of flooding … that’s going to have to be dealt with.” Such damaging events have already happened elsewhere on the globe.
Earthquake-driven coastal subsidence followed recent earthquakes in Chile, Alaska, Southeast Asia and Japan, resulting in such severe consequences as permanent land loss, widespread infrastructure damage and forced relocation.
These risks are exacerbated by climate-driven 21st century sea-level rise. In some communities along the coastal Washington, Oregon and northern California, the effects of sea-level rise are somewhat moderated by gradual coastal uplift. In fact, coastal uplift rates exceed the current rate of sea-level rise in such places as Astoria, Ore., Port Orford, Ore., and our neighbor to the north, Crescent City.
Humboldt Bay residents aren’t so lucky. Here, the study’s authors note, “complex regional tectonics are causing gradual subsidence, resulting in the highest recorded Pacific-coast RSLR [relative sea-level rise] rate of 4.7 [millimeters per year].” In other words, the ground beneath our feet is slowly dropping as the water rises.
earthquake-driven subsidence are amplified by climate-driven sealevel rise. | Creative Commons license CC-BY-NC-ND 4.0. ###
The study defines a “major earthquake” as a magnitude 7.7 to 9.2, and while that may sound unlikely (knock wood), scientists were able to discover how often they occur by radiocarbon-dating plant fragments preserved within pre-earthquake peat or overlying mud. The results? There have been 11 such “great earthquakes” along Cascadia’s coasts over the past 6,000-7,000 years. They hit roughly every 200 to 800 years.
The most recent “great earthquake” along the Cascadia subduction zone struck in 1700 — more than 300 years ago. The CSZ is a major offshore fault line running from Northern California to British Columbia.
The authors of the new study warns that coastal flood hazard analysis often overlooks the risk of sudden earthquake-triggered land subsidence.
“This study underscores the need to consider combined earthquake and climate impacts in planning for coastal resilience at the Cascadia subduction zone and globally,” it says.
The combined effects of earthquake subsidence and climate-driven sealevel rise could more than triple the flood exposure of residents, structures and roads in the next 75 years, the study found. The coastal areas at risk are home to airports, major highways, wastewater treatment facilities, businesses and homes.
County leaders recently completed a Sea-Level Rise Adaptation Plan for Humboldt Bay/Eureka Slough Area. It advocates “an incremental approach” to planning, using various “shorter-term actions” to reduce immediate risk and buy time for more ambitious “longer-term actions” to address future conditions. It does not appear to contemplate the possibility of long-term projections becoming a reality all at once.
Tsunamis along the Cascadia Subduction Zone can be triggered in a mega earthquake when the Juan de Fuca plate is rapidly pushed underneath the North American plate, displacing massive amounts of water. That same movement can cause coastal land to suddenly drop, according to Dura, an assistant professor in geosciences at Virginia Tech.
If that happens, she recently told the San Francisco Chronicle, “All the sea-level rise you expected by 2300 is going to happen in minutes.” You can download the study and read it for yourself via the link below. The study was funded by the Cascadia Region Earthquake Science Center, part of the National Science Foundation. ###
DOCUMENT: Increased flood exposure in the Pacific Northwest following earthquake-driven subsidence and sea-level rise