Oblique aerial photo showing the Lanphere Dunes (foreground) and Mad River Slough (background)

Skeletal forest, Humboldt Bay Dunes

Transverse dune front and vernal pool

Invasive Yellow Bush Lupin in flower

Advancing dune front and adjacent coastal forest
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Location: Humboldt County, California
Client: Humboldt County Planning Department
Project Lead(s): Bill Weaver
Services: Geology and Geomorphology Consulting

This study was a resource investigation conducted to provide data and recommendations regarding the condition and effects of possible management and recreation strategies being considered for the coastal dune systems in the Humboldt Bay area.  The coastal dune fields bordering the western margin of Humboldt Bay contain some of the most extensive and least disturbed dune environments in California, while some other areas have been heavily impacted by development and recreational vehicle use. Although northern portions of the dune system are locally intact and operating as they would under natural conditions, decades of residential development, recreational activities, and non-native plant invasion in many areas necessitated an evaluation of the historic and current geomorphic conditions. This project was undertaken as a part of a larger planning process that ultimately led to adoption of a long term, sustainable beach and dunes management plan that was consistent with environmental conservation and county coastal development goals.
Specifically, Pacific Watershed Associates was contracted to:

  • Conduct a literature review and compile information on physical processes which control this and similar coastal dune systems
  • Review local shoreline processes, and discuss their possible effects on coastal dune processes
  • Map active and currently dormant coastal dune fields
  • Identify and describe human-caused disturbances to the dune system and environment, and determine the relative susceptibility of various dune forms to accelerated erosion
  • Outline methods for monitoring and quantifying future human disturbances on dune processes and forms
  • Outline various management recommendations, strategies, and techniques which can be employed to limit unnecessary damage to the physical dune system resulting from future recreational activities  

Since completion of this coastal dune assessment PWA has completed geomorphic analyses related to potential development, recreational use, and restoration options for the Tomales Dunes in Marin County, McKerricher Dunes in Mendocino County, and Tolowa Dunes in Del Norte County