Levee and Flood Management
The Federal Emergency Management Agency (FEMA) develops Flood Insurance Rate Maps (FIRMs) as a tool for identifying flood risks. Areas mapped as Zone “A” (Special Flood Hazard Area) on a FIRM are subject to special building standards and may be subject to flood insurance requirements by lending institutions. FEMA is in the process of updating the FIRMs for Humboldt County to more accurately characterize flood risk. The FEMA flood maps are being updated in two phases:
The most recent FIRMs became effective on November 4, 2016. This update reflects the results of detailed flood studies in certain areas, changes in the vertical datum, and conversion to a digital platform. These maps are available at the FEMA Map Service Center and the Humboldt County Web-GIS.
Flood maps along the coast are being updated to reflect the results of FEMA’s Open Pacific Coast Study, which was an engineering study to evaluate coastal flood hazards. The preliminary maps are available for review on this site Coastal Flood Maps.
- FEMA Open Pacific Coast Study – Nearshore Hydraulics (September 2014) – (PDF 3.6 MB)
- Presentation on FEMA flood map updates at the Humboldt Bay Symposium (October 22, 2016) – (PDF 18.5 MB)
- New draft coastal flood maps that will become effective in mid-2017
- Humboldt County’s flood damage prevention ordinance – (PDF 1.3 MB)
- FEMA Map Service Center
- Humboldt County Web-GIS
Jacobs Avenue Levee
The Jacobs Avenue Levee is situated along Humboldt Bay between the Highway 101 Eureka Slough bridge and Airport Road. The one-mile-long levee provides flood protection for 31 parcels within Eureka city limits. The Jacobs Avenue Levee does not have a single owner; rather, multiple property owners own portions of the levee adjacent to their respective properties. Humboldt County owns a 3.2-acre parcel behind the levee which serves as the County’s vehicle maintenance facility and heavy equipment yard.
In 2014, Humboldt County (acting as the Humboldt County Flood Control District) initiated a technical study of the Jacobs Avenue Levee to assess the stability of the levee and its associated flood risks, and to determine whether the levee meets FEMA’s certification standards. Funding for this study was provided by the California Department of Water Resources, Humboldt County, City of Eureka, and affected private landowners along Jacobs Avenue, with laboratory testing performed by Caltrans.
Redwood Creek Levee
The Redwood Creek Flood Control Project in Orick consists of a system of two earthen embankment levees along the lower 3.4 miles of Redwood Creek. The project was constructed by the U.S. Army Corps of Engineers from 1966 to 1968 to protect the community of Orick from floodwaters, in response to a series of flood events that occurred in 1950, 1953, 1955 and 1964. Construction included excavation and enlargement of the channel to a target geometry and placement of earthen levee embankments along each bank. Humboldt County performs levee operation and maintenance.
The Flood Control Project is impaired by the deposition of large volumes of sediment, which has reduced the project’s flood capacity from the level of protection specified by Congress. Construction of the levees also reduced the ability of North and South Sloughs to flush sediment, which contributes to flooding of adjacent privately owned pastures and public roads. A fundamental rehabilitation of the Flood Control Project is needed to accommodate sediment inflow and achieve an acceptable level of flood protection that can be sustained with normal maintenance. Improvements are needed to regain active status in the Corps of Engineers Rehabilitation and Inspection Program and achieve certification and accreditation on the FEMA Flood Insurance Rate Map.
Construction of the Flood Control Project caused major physical changes to the lower reach of Redwood Creek and its estuary. Estuary volume has been reduced by over one-half of its pre-levee size due to sediment deposition, and fish habitat and water quality have been severely impaired. The net result has been a reduction in the ecological function of the estuary in terms of productivity and survival of fish and other aquatic species. Restoration of hydraulic, sediment transport, and floodplain processes is needed to help the estuary regain some of its former form, function, resiliency, and productivity.
In 2014, Humboldt County completed a planning study which developed conceptual designs for a multiple-objective project on lower Redwood Creek and estuary that would achieve estuary restoration and levee rehabilitation. Funding was provided by the California Department of Fish and Wildlife (formerly Department of Fish and Game) through the Fisheries Restoration Grant Program. The approach to this planning study focused on facilitating stakeholder dialogue and improving the understanding of natural processes, desired conditions, and potentially feasible project concepts.
Mad River Levee (Blue Lake)
The Mad River Flood Protection Project is located near the confluence of the Mad River and the Mad River North Fork, along the right bank of each waterway for a total length of 1.6 miles, near the Hatchery Road bridge at the southern end of the city of Blue Lake. The levee was constructed in phases by the Army Corps of Engineers starting in 1954 and reaching completion in 1963. The levee is composed of an earthen embankment with rock-slope protection on the river side. Humboldt County and the City of Blue Lake share responsibility for levee operation and maintenance.
In 2015, Humboldt County and the City of Blue Lake completed a geotechnical investigation with financial assistance from the California Department of Water Resources to characterize subsurface soil conditions and analyze levee performance. The project assessed the stability of the levee embankment and foundation and evaluated the potential for settlement, seepage, underseepage, or erosion to cause instability under base flood (1%-annual-chance flow) conditions.
Eel River Levee (Fortuna)
The Eel River Flood Control Project at Sandy Prairie is located along the right bank of the Eel River, with extensions along Strongs Creek and the Van Duzen River, near the city of Fortuna. The levee was constructed by the Army Corps of Engineers and completed in 1959. The total length of levee is approximately four miles.