Humboldt Bay Sea Level Rise Adaptation Planning Project

Recent Updates
Humboldt Bay Sea Level Rise Meeting Notice 11-12-2014
Agenda - HBSLRAP Project Public Meeting  11-12-2014

Agricultural Lands White Paper
Highway 101 Corridor White Paper

April 2014 Inundation Maps (zip file download)
Humboldt Bay Shoreline Inventory, Mapping and Sea Level Rise Vulnerability Assessment Report
Addendum - Humboldt Bay Shoreline Inventory, Mapping and Sea Level Rise Vulnerability Assessment Report 

APWG Agenda 02-27-2013
APWG Agenda 04-24-2013
APWG Agenda 07-16-2013 
APWG Agenda 08-28-2013
APWG Agenda 10-30-2013
APWG Public Meeting 11-12-2013

APWG Agenda 02-26-2014
APWG Agenda 04-30-2014
APWG Agenda 06-25-2014 
APWG Agenda 08-27-2014 
APWG Agenda 10-29-2014

Sea Level Rise
Humboldt Bay Sea Level Rise Adaptation Planning Project
Existing Conditions
Vulnerability Assessment
Risk Assessment
Adaptation Planning
Contact Us
Agency List
Project Informational Documents
APWG Meeting Schedule
Current News and Information
Related Links

Sea Level Rise (top)
The increase in global temperature has raised sea level by 7 to 8 inches over the past century.  On Humboldt Bay, sea level rise is greater because we live in a seismically active area and the ground has been dropping in elevation.  Consequently, sea level in the Bay may have increased by more than 18 inches over the past century.  The National Research Council has projected that sea level may rise by as much as 55 to 65 inches in California by 2100.  Communities around Humboldt Bay will need to prepare for the effects of sea-level rise, which could severely impact critical infrastructure such as our wastewater treatment plants, Highway 101 corridor, our port, and residential communities, businesses, and coastal agricultural lands.

King Tide 2010 Swain Slough

Humboldt Bay Sea Level Rise Adaptation Planning Project (top)
The State Coastal Conservancy is funding a multi-phased sea-level rise project on Humboldt Bay.  The first phase completed in January 2013 was the Humboldt Bay Shoreline Inventory, Mapping and Sea Level Rise Vulnerability Project and the second phase currently underway is the Humboldt Bay Sea Level Rise Adaptation Planning Project.  The Coastal Ecosystems Institute of Northern California is the project sponsor for the second phase.  There are two components of the second phase: inundation modeling and mapping that Northern Hydrology and Engineering is preparing, and adaptation planning that the Humboldt Bay Harbor, Recreation and Conservation District along with Humboldt County Public Works are implementing as co-lead agencies.  Trinity Associates is the adaptation planner for the Adaptation Planning Working Group that the District and County have convened. 

King Tide Tuluwat

Existing Conditions (top)
The first phase of the project inventoried and mapped the Bay’s 102 miles of shoreline and found that 75% of the shoreline is artificial.  This is an important finding as artificial shoreline structures such as earthen dikes must be maintained if the lands behind them are to be protected.  The Bay’s artificial shoreline is predominately (67%) made of two types of structures: earthen dikes (53%) and railroad grade (14%).  If these structures are breached or overtopped during King Tides, storm surges, El Nino conditions, or from sea level rise, thousands of acres of former tidelands that are vulnerable would be flooded by the tides.

Artificial Shoreline         Dike And Rail
Artificial (red) vs. Natural (green)                                           Dike (yellow) and Railroad (red)

Vulnerability Assessment (top)
To assess shoreline vulnerability, this project has selected a baseline elevation of the mean monthly maximum high tide elevation (7.74 feet) as measured at the North Spit tide gage.  Shoreline vulnerability was rated based on a combination of shoreline cover (exposed, vegetated, and fortified) and elevation in relation to the baseline elevation of 7.74 feet.  The inventory of the Bay’s shoreline found that currently there area 21 miles of dikes and 5 miles of railroad grade that are rated highly vulnerable.

Vulnerability Rating

                                     Vulnerability Rating: High (red), Moderate (yellow), and Low (green)

During the second phase of this project, an inundation model has been developed to map the areas that are vulnerable to flooding at the baseline tide elevation if shoreline structures are breached or overtopped.  It is not surprising that the area that is vulnerable to flooding is nearly the same area of former tidelands that were diked and drained over a century ago.  Models are also being created to map the areas that would be flooded with 1, 2, 3 and 6 feet of sea level rise.  These models will also indicate the areas subject to flooding by a 100 year flood event.

Inundation Model

Risk Assessment (top)
Sea level rise’s primary impact on Humboldt Bay will be flooding and secondarily salt water intrusion.  The maximum high tides of the year are called King Tides and the average is 8.78 feet at the North Spit tide gage.  But in a few years, King Tides have reached as high as 9.5 feet, which is nearly 2 feet of sea level rise, and dikes were overtopped or breached.  Much of our communities’ critical infrastructure is at risk from tidal flooding because they were constructed on vulnerable former tidelands: For example, Highway 101, Eureka’s and Arcata’s wastewater treatment plants, and miles of water-gas-electrical transmission lines are located behind earthen dikes or railroad grade on former tidelands.  There are also public facilities, businesses, residential communities, and agricultural areas that are at risk from tidal flooding if the shoreline is breached or overtopped or by sea level rise.  We must plan for a future of rising tides while the ground is subsiding and sea level is rising if we are to protect the communities on Humboldt Bay

Risk Assessment

Adaptation Planning (top)
The Humboldt Bay Harbor, Recreation and Conservation District and Humboldt County Public Works together have formed the Adaptation Planning Working Group whose members include staff from the Planning and Public Works Departments for Humboldt County and the Cities of Eureka and Arcata, Coastal Ecosystems Institute of Northern California, State Coastal Conservancy, Coastal Commission’s North Coast District office, Wiyot Tribe, Humboldt Bay National Wildlife Refuge, Department of Fish and Wildlife, US Fish and Wildlife Service, Bureau of Land Management, and National Resources Conservation Service.  The goal of the project is to support informed decision-making and encourage a unified, consistent regional adaptation strategy to address impacts associated with sea level rise in the Humboldt Bay region.  Sea level rise adaptation planning begins with understanding existing conditions, assessing what areas are vulnerable and what assets are at risk, and developing Bay-wide unified adaptation strategies to deal with flooding.

Planning Strategy

Contact Us (top)

Jack Crider, Executive Director

Hank Seemann, Deputy Director
Environmental Services
Humboldt County Public Works Department
(707) 445-7741

Aldaron Laird

Adaptation Planner
Trinity Associates
(707) 825-8770

Agency List (top)

  • Dan Berman, Humboldt Bay Harbor, Recreation, and Conservation District
  • Hank Seemann, Humboldt County
  • Aldaron Laird, Trinity Associates
  • Jeff Anderson, Northern Hydrology & Engineering
  • Joel Gerwein, State Coastal Conservancy
  • Jill Demers, Coastal Ecosystems Institute of Northern California
  • Rob Wall, City of Eureka
  • Lisa Shikany, City of Eureka
  • Riley Topolewski, City of Eureka
  • Bruce Young, City of Eureka
  • Scott Ellsmore, City of Eureka
  • Mark Wheetley, City of Arcata
  • Larry Oteker City of Arcata
  • Doby Class, City of Arcata
  • Mark Andre, City of Arcata
  • Kevin Hamblin, Humboldt County
  • John P. Miller, Humboldt County
  • Cybelle Immitt, Humboldt County
  • Stephen Kullmann, Wiyot Tribe
  • Bob Merrill, Coastal Commission
  • Melissa Kraemer, Coastal Commission
  • Melanie Faust,Coastal Commission
  • Jim Baskin, Coastal Commission
  • Rex Jackman, Caltrans
  • Leishara Ward, Caltrans
  • Sherry Constancio, Caltrans
  • Jaime Hostler, Caltrans
  • Gordon Leppig, Dept. Fish & Wildlife
  • Vicki Frey, Dept. Fish & Wildlife
  • Eric Nelson, US Fish & Wildlife Service
  • Paula Golightly, US Fish & Wildlife Service
  • Dave Fuller, Bureau Land Management
  • Jonathan Shultz, National Resources Conservation Service
  • Troy Nicolini, NOAA's National Weather Service
  • Becky Price-Hall, Humboldt Bay Initiative
  • Joe Tyburczy, California Sea Grant Extension
Project Informational Documents (top)
  • Existing conditions (TBA)
  • 100 year flood inundation maps (TBA)

APWG Meeting Schedule (top)
The APWG will meet bi-monthly the last Wednesday of the month from 1:00 to 3:00pm at the Humboldt Bay Harbor, Recreation and Conservation District.
2013 - 12/18
2014 -   2/26,  4/30, 6/25, 8/27, 10/29
2015 - 1/7

Current News and Information (top)

Humboldt Bay Sea Level Rise Adaptation Planning Project 

Related Links (top)