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This chapter highlights information on public hazards and community resource values presented in the Technical Background Report to the Carlotta/Hydesville Community Plan. Hazard information summarized in the Technical Background Report covers the identifiable hazard issues within the planning area, such as geologic fault rupture, flooding, drainage, noise and airport safety. Also included are natural and cultural resource values such as fish and wildlife habitat, historic buildings and archaeological sites.
REFER TO CHAPTER 3 OF THE FRAMEWORK PLAN FOR ALL HAZARD AND RESOURCE POLICIES APPLICABLE IN THE CARLOTTA/HYDESVILLE COMMUNITY PLAN.
Geologic Fault Rupture
Surface ruptures along faults are site-specific hazards limited to the areas adjacent to active faults and branches of active faults. In 1972 in response to the fault rupture hazards, the State enacted the Alquist-Priolo Act establishing Special Studies Zones along well defined active faults to prohibit the location of some structures for human occupancy across the traces of active faults to reduce the hazard of fault-rupture. The Act exempts single-family wood frame dwellings not exceeding two stories when such dwelling is not part of a development of four or more dwellings.
Because of the large number of potentially active faults in California faults are only zoned if they are considered to have a relatively high potential for future activity and to have reasonably well-defined surface traces. The California Division of Mines and Geology (CDMG) Fault Evaluation Report FER-130, dated August 31, 1982, evaluates the Goose Lake and related faults (known as Fault A) in the Carlotta/Hydesville Community Planning Area. FER-130 concludes that both faults are reasonably well defined with fairly conclusive evidence of fault movement sufficient to warrant the Special Studies Zone designation.
Flood Hazard
Historic data indicates the Van Duzen River is in a stage of aggradation (a rise in the elevation of the channel bed) as a result of increased bedload sediment being deposited. This rise in riverbed elevation typically leads to higher frequency of flooding, increased erosion and deposition, loss of agricultural lands, and riparian habitats and destruction of anadramous fish spawning beds.
A large snow pack and intense rains contributed to the devastating flood of 1964. Although the majority of damage occurred on the Eel River delta, the lower Van Duzen River area suffered $4,000,000 in damages. The Cuddeback- Fielder Creek area in Carlotta and the settlement at Starvation Flats on the Van Duzen River received extensive flood damage.
Although extensive flood damage has occurred on the Van Duzen River in the
past, studies indicate that similar and even larger floods can be expected to occur in the future. Heavy rainfalls in the narrow river canyon coupled with a gradually rising riverbed contribute to the increasing frequency of major floods. A fundamental way to avoid the hazards of flooding is by minimizing development within the river flood plain.
Flood control studies of the Van Duzen River have evaluated dams, dikes and dredging. Extensive investigations by the Department of Water Resources and the Bureau of Reclamation indicate that the geological instability of the Van Duzen basin precludes large dam construction. Some levees and bank protection works have been constructed by local citizens and industries. Efforts applied by individual landowners are usually not sufficient to control the damages caused by severe floods, but may, be effective against smaller flood peaks. Channel dredging solutions have been studied by engineers, hydrologists, oceanographers and others. In general, their conclusion is that it is neither physically possible nor economically practical. The Eel River-Van Duzen River system produces an average annual sediment (suspended plus bedload) yield of 32.5 million tons. The Corps of Engineers estimates that 80 million cubic yards would have to be removed annually in order to maintain flood capacity.
Part of the Federal Government's response to increasing flood damages has been the establishment of a National Flood Insurance Program. The Federal Emergency Management Agency (FEMA) manages the program which consists of two major parts. The first part is the mapping and local regulations of 100-year flood plains. Flood areas have been mapped and the County has adopted a building ordinance which regulates construction in the 100-year flood plains to limit future flood damages. Figure 3 shows the general location of the 100-year flood plains of the Van Duzen River and Yager Creek and the two most critical drainage problem areas within the planning area.
The second part of the program is flood insurance protection. New development in the 100-year flood plain which is financed by federal funds or federally insured financial institutions is required to purchase flood insurance. Existing development is offered subsidized insurance to share the risk of flood damage between the property owner and the Federal Government. The two parts of the program together attempt to reduce future flood damage and hardship. Humboldt County participates in the regulatory program to have flood insurance made available to the citizenry.
The growth and development of the community of Hydesville (population 900), two major sawmills and surrounding lands reserved for additional industrial development, redevelopment within the historic Carlotta townsite and the continuation of agriculture within the Yager Creek Valley may all be dependent on the water resources of Yager Creek. The agricultural community has expressed concerns about the ability of Yager Creek to fully provide for both agricultural and urban water needs. Although Yager Creek is a major tributary to the much studied Van Duzen River, little information has been developed or collected about the groundwater within the Yager Creek Valley.
The County supports and encourages the preparation of a water resource study of Yager Creek.
Standard
Such study should include, but not be limited to, an assessment of in- stream needs and the location and extent of the groundwater aquifer.
Implementation
The County should assist in the coordination of the Hydesville County Water District, other Yager Creek Groundwater users, State Department of Fish and Game, State Department of Water Resources and other interested parties to provide technical and/or financial assistance.
Streams and streamside areas are identified by the County General Plan as sensitive habitats and are subject to Framework Plan Policies aimed at restoring and maintaining these areas.
Wolverton Stream and other tributaries to the Van Duzen River are reported to have both silver salmon and steelhead runs. A preliminary field survey of Wolverton Stream by the Redwood Community Action Agency: notes the occurrence of silver salmon and king salmon; generally identifies the types of existing impacts on the stream environment; and, recommends that a complete survey of Wolverton Stream be undertaken.
The County supports and encourages private and public cooperative efforts to restore and maintain the fish habitat values of Wolverton Stream.
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