Sea Level Rise and Coastal Adaptation Planning
With almost half of the US population living within 50 miles of a coastline, climate change will have widespread impacts on the nation’s economy and environment. The Humboldt Bay region is expected to experience the highest rate of sea level rise in California as a result of combined effects from sea level rise and land subsidence associated with the Cascadia subduction zone (large tectonic vertical land motions). Relative sea level rise projections indicate that the elevation of average high tide in Humboldt Bay could could rise 49.3 – 173.5 cm (0.5 – 1.7 meters) by the year 2100. A significant portion of the County’s critical transportation, communications, electricity, water supply, and public infrastructure is therefore at risk from the threat of sea level rise.

The Humboldt Bay Sea Level Rise Vulnerability and Adaptation Planning Project identified sea level rise vulnerabilities to support informed decision-making and encourage a unified, consistent regional adaptation approach.  Funded by the State Coastal Conservancy’s Climate Ready Grant Program, the project builds on previous work (Phase I, see below) by Trinity Associates completed in January 2013 and is a partnership between CEINC and the Humboldt Bay Harbor, Recreation and Conservation District; Trinity Associates; Northern Hydrology and Engineering; and the County of Humboldt.

Documents and GIS Products

 

A component of the project identified sea level rise vulnerabilities in Humboldt Bay through a detailed technical study led by Northern Hydrology and Engineering (NHE) and consists of the following work products:

  1. SLR hydrodynamic modeling to develop inundation vulnerability maps of areas surrounding Humboldt Bay vulnerable to inundation from existing and future sea levels. A final report is now available along with SLR inundation vulnerability files in Google Earth KMZ files and ArcGIS shape files.
    HBSLR Modeling Inundation Mapping Report (Northern Hydrology 2015)
    Google Earth KMZ Files (Northern Hydrology 2015)
    ArcGIS Shape Files (Northern Hydrology 2015)
  2. A seamless topographic/bathymetric digital elevation model (DEM) of Humboldt Bay using the recent 2009-2011 California Coastal Conservancy LiDAR Project Hydro-flattened Bare Earth DEM (California Coastal DEM) and various subtidal bathymetric data sets to support the modeling efforts. Pacific Watershed Associates (PWA) conducted this work in 2014.
    Humboldt Bay DEM (developed by Pacific Watershed Associates – links to Google Drive to download)
    HBSLR Project DEM Development Report (Pacific Watershed Associates 2014)
  3. A conceptual groundwater model to analyze the effects of SLR on groundwater levels and saltwater intrusion in the Eureka-Arcata coastal plain. Dr. Robert Willis conducted this work in 2014.
    HBSLR Conceptual Groundwater Model (Willis 2014)

Phase I
The Humboldt Bay Shoreline Inventory, Mapping and Sea Level Rise Vulnerability Project was the first phase of this project inventoried and mapped Humboldt Bay’s 102 miles of shoreline. Download the Phase 1 reports here:

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

Sea level rise will, by definition, occur within the Coastal Zone where multiple agencies have jurisdiction. Planned response will therefore require a high level of inter-agency coordination. The following adaptation planning projects support the development of a unified, consistent regional adaptation strategy to address sea level rise impacts in the Humboldt Bay region.

 The Humboldt Bay Sea Level Rise Adaptation Planning Working Group (APWG) was convened by Humboldt Bay Harbor, Recreation and Conservation District and Humboldt County Department of Public Works Department. The APWG is composed of 22 regional stakeholders with land use, land management, resources management responsibilities, or management advisory roles on lands adjacent to Humboldt Bay that are vulnerable to sea level rise impacts. More information about the APWG can be found at http://humboldtbay.org/humboldt-bay-sea-level-rise-adaptation-planning-project

The Humboldt Bay Sea Level Rise Adaptation Plan prepared by Trinity Associates explores all aspects of sea level rise and adaptation planning on Humboldt Bay, and includes-depth adaptation planning case studies for two critical regional assets that are at risk from sea level rise—agricultural lands and uses and the Highway 101 corridor.
Humboldt Bay Sea Level Rise Adaptation Planning Project Phase II Report (Laird 2015)

Related projects with some HBI involvement or participation:

  • Humboldt Bay National Wildlife Refuge Sea Level Rise Modeling
  • Humboldt Bay Vertical Reference System Work Group