The morphology of the Lower Eel River Basin has been changed due to erosion and aggradation:
The Lower Eel River Basin has undergone considerable sedimentation and deposition, which has resulted in:
● An overall decrease in tidal prism and shallowing of the estuary and riverbed (Williams 1988);
● Loss of estuarine habitat area and diversity;
● Loss of spawning area for salmonids due to excess siltation of gravel beds (Reynolds et al., Stream Inventory Reports, CDFG spawning surveys);
● Intermittent and periodically dry reaches in tributaries and lower mainstem Van Duzen River during low summer and autumn flows (Williams 1988), (Reynolds et al. 1981) (CDFG field surveys);
● Highly channelized streams (Reynolds et al. 1981);
● Reduction of riparian vegetation on stream banks;
The Lower Eel Basin is very seismically active, resulting in extensive surface erosion, uplift and landslides (Reynolds et al. 1981, PALCO Van Duzen Watershed Analysis, 2002);
Large seasonal storms result in flooding and stream channel modification.
Historic and current land use has altered watershed processes and conditions:
Agricultural lands now dominate what was historically forested riparian, and wetland habitat throughout the Lower Eel River Basin (Williams 1988, Monroe et al. 1974, Roberts 1992);
There has been an overall change in species of grass for the purposes of grazing, which has reduced the root strength of prairie vegetation, increasing slumping in upper reaches of the system, like the North Fork Eel River (Reynolds et al. 1981);
Livestock have unrestricted access in some streams of the Lower Eel Basin causing stream bank erosion and riparian vegetation damage (ERWIG, P. Halstead pers. comm.);
Filling, draining and diking of streams has been required to allow for residential development in the Middle Subbasin (Roberts 1992);
Most of the streams of the Middle Subbasin run through urban areas and as such, are subject to input of polluted storm runoff and garbage (Halstead pers. comm., Yazzolino pers. comm.);
Basin-wide disturbance activities, including timber harvesting practices, gravel mining, road construction, residential development, land subdivision activities and grazing have caused an increase in sedimentation in the entire Eel River Basin (Williams 1988, Monroe et al. 1974, CDFG 1997 [Eel River Action Plan]);
Dredging and filling, gravel and sand mining, dams and water diversions have contributed to the Eel River estuary’s dynamic position of its main channel (Puckett 1977);
Water quality is degraded through runoff from dairy operations, urban wastewater,and urban storm water (Roberts 1992, Monroe et al. 1974, Yazzolino pers. comm.);
Streambank erosion above and below Fernbridge has caused loss of pasture and could be a threat to the bridge and the Humboldt Creamery’s Wastewater Treatment Plant.
Alterations to watershed processes have affected the basin both socially and economically:
The Salt River of the Eel River estuary is no longer navigable by sea-going ships;
Seasonal drainage problems are becoming more frequent in residential and business areas, which can prove costly for private land owners and public entities (Downie and Lucey 2005);
In order to address drainage issues, the city of Fortuna would need to spend approximately $10 million, which is well beyond the available budget (approximately $300,000). State and federal funding that the city does receive is already earmarked for mandated sewage and drinking water regulations (W. Yazzolino, pers. comm.);
Fortuna and Loleta have lost substantial tourism dollars because they can no longer advertise as major fishing venues due to low flows and reduced salmon numbers (W. Yazzolino, pers. comm.);
Increased development has introduced construction wastes to the watershed through storm drains. The city of Fortuna is not monitoring water quality changes with regards to storm runoff, though it is beginning to address these issues associated with development through the creation of regulatory programs.
Fish and wildlife have been adversely impacted by current watershed conditions in the Basin:
Stream channelization, water control practices, barriers to fish migration in the form of levees and dikes, and sedimentation have resulted in a decreased ability of the Basin to support anadromous fisheries (Monroe et al. 1974);
Spawning areas are affected by sediments trending toward increasing fines, and decreasing geometric mean particle size, and compaction of spawning gravel (PALCO Van Duzen Watershed Analysis 2002, Monroe et al. 1974);
Stream aggradation has resulted in loss of rearing habitat in the estuary, as well as increased water temperatures resulting in decreased dissolved oxygen (Monroe et al. 1974);
Aquatic macroinvertebrates are affected by increased sedimentation in streams and loss of estuary habitat (Monroe et al. 1974, Williams 1988);
Riparian vegetation has been reduced throughout the study area, resulting in a decrease in shade canopy and recruitment of large wood to streams (Reynolds et al. 1981);
Upstream migration of fish is restricted during early autumn dry periods, particularly in the lower Van Duzen River (PALCO Van Duzen Watershed Analysis 2002) and Eel River just above the Van Duzen confluence. This has led to stranding mortality in early fall Chinook salmon;
Fish passage is additionally affected by culverts and tide gates.
Flow and Water Quality Improvement Activities
Increase the tidal prism to help to maintain existing channels and help remove excessive fine sediment accumulations;
Conduct an inventory of tide gates and levees in the watershed;
Where necessary, identify barriers to fish migration in the form of large debris accumulations, culverts, etc. and modify them;
Livestock management fencing should be placed in areas where cattle have unrestricted access to streams.
Erosion and Sediment Delivery Reduction Activities
The impact of property subdivision on streams of Lower Eel River Basin should be minimized through the use of better land management practices. Opportunities to acquire conservation easements should be examined;
Conduct an upslope erosion inventory on streams in the Middle and Upper Subbasins in order to identify and map stream bank and road-related sediment sources. Sites should be prioritized and improved in order to decrease sediment contributions within the basin;
Encourage the use of cattle exclusion fencing along streams where livestock have unrestricted access;
In streams where spawning area is limited, projects should be designed to trap and sort spawning gravels in order to expand and enhance redd distribution.
Riparian and Habitat Improvement Activities
Identify and prioritize locations within the delta where vegetation can be returned to salt tolerant species, thus increasing salt marsh around slough channels and providing a buffer to adjacent lands during inundation;
Programs to increase riparian vegetation should be implemented in streams where shade canopy is below target values of 80% coverage. Additionally, those streams that are vegetated with exotic species should be considered for native plant restoration;
In creeks where fish spawning and rearing habitat is limited, pool enhancement and instream structures should be added to increase complexity;
In order to protect riparian vegetation, and decrease stream bank erosion due to unrestricted access of cattle to streams, use of livestock management fencing should be prescribed;
Log debris accumulations in streams that retain high levels of fine sediment should be assessed, and carefully removed where appropriate.
Education, Research, and Monitoring Activities
Improve educational outreach to community;
Encourage and partner with Fortuna Creeks Project’s urban stream clean-up, habitat restoration and monitoring;
Support the Humboldt County Resource Conservation District in its efforts to monitor and improve habitat and water quality in the basin;
Because water quality data are limited, monitoring of summer water temperatures should be preformed over at least a 3- to 5- year period;
Water quality data, including temperature and dissolved oxygen, should be consistently collected throughout the year, for several years, in order to accurately characterize conditions in the streams. Salinities should be collected in the estuary and upstream to determine the extent of brackish conditions;
Conduct habitat and fish inventories on urban streams of the Middle Subbasin, including Palmer, Jameson, and Rohner Creeks and unnamed tributaries to Strongs Creek;
Partner with local academic institutions and private agencies as a means to encourage the study of the fish and habitat.