Issues

Urbanization and increased residential development have generated negative effects on streams;

There is concern about unrestricted stream access of livestock in agricultural areas;

Erosion related to timber harvest on unstable soils is a concern;

There is concern about the impact of gravel mining on the mainstem Eel River;

Instream habitat conditions for salmonids are thought to be poor.

Findings

Urbanization and increased residential development have generated negative effects on streams.

Altered flow regimes

Low summer flows are exacerbated by land and stream disturbances and result in dry or intermittent reaches on streams, which are stressful to salmonids;

Fortuna operates five groundwater extraction wells near the Eel River;

Fortuna operates five groundwater extraction wells near the Eel River;

Many of the storm drains and culverts in Fortuna are undersized (Winzler and Kelly 2005), increasing the velocity of flows during precipitation events;

Strongs and Rohner creeks have been modified where they flow through Fortuna to eliminate their floodplains, increasing the volume and velocity of flows during precipitation events;

Winter floods are increasingly common due to high winter precipitation levels, increased runoff, and undersized storm water drainage structures. Areas with current flooding include the North Fortuna Drainage Area, Rohner Creek, the lower reaches of Strongs Creek, and Jameson Creek at the confluence with Strongs Creek (Winzler and Kelly 2005);

Undersized drainage capacity has also been identified in several areas including Rohner Creek and the Mill Creek drainage. Rohner Creek has the highest potential for serious flooding (Winzler and Kelly 2005).

Addition of pollutants

When flows are sufficiently high, the Eel River floods into treatment ponds of the Fortuna Wastewater Treatment Plant;

The Fortuna Wastewater Treatment Plant received a cease and desist order in 1997. The issue was resolved and the order was rescinded that same year;

The treatment plant had three chlorine limit violations - one maximum and two minimum values that violated the permit level in 2004. Sewer overflows that occurred in the system were caused by high flows and collection system stoppages;

Increased development in Fortuna, especially in the southern and eastern parts of the city, has increased runoff from newly created impervious areas (FEMA 1981 cited in Mintier and Associates 2006). Although no specific tests of chemicals have been conducted in Fortuna’s streams, urban runoff in general is known to mobilize chemicals such as trace elements, pesticides, copper, and volatile organic compounds (Hamilton et al. 2004);

Livestock grazing likely occurs in 23% of subbasin and has been noted along Strongs and North Fork Strongs creeks. Although no specific tests of nutrients and/or coliform bacteria have been conducted in these creeks, levels of these constituents often exceed water quality standards in areas with extensive livestock use;

The Humboldt Creamery located just downstream of Fernbridge on the Eel River has a wastewater discharge permit.

Fish passage barriers where roads cross streams

A culvert on Mill Creek (RM 1.3) and Rohnerville Road does not meet CDFG and NOAA Fisheries fish passage guidelines;

Palmer Creek has problems with fish passage due to a barrier in the 800 foot culvert under Highway 101.

Erosion from roads, construction wastes, and ground disturbance

Natural erosion rates are high due to:

   ● The major rock underlying the subbasin is alluvium, which constitutes 70% of the subbasin. The other bedrock, also sedimentary, is Pliocene marine. Both of these geologic types are highly erodible;
   ● Rapid incision rates of the mainstem and its tributaries have left a series of river terrace deposits perched steeply above the current stream channels which contribute fine sediments through slope instability and dry ravel;
   ● The Little Salmon fault cuts through this basin, weakening bedrock and increasing the potential for seismic triggering of landslides;
   ● During the winter rainy season, heavily silted water flows through the steep upstream terrain, which affects turbidity and sediment levels in streams.

Changes in basin due to land use:

   ● Sedimentation and in-filling as a result of land development and subdivision activities, gravel mining and timber harvesting practices have resulted in an overall reduction in channel area, and consequently in available salmonid habitat;
   ● Fortuna grew from one square mile in 1950 to 4.68 square miles in size in 2006. This represents a change from approximately 4% to 19.5% of the subbasin;
   ● The Fortuna annual average population growth rate from 1980 to 2005 was 1.6%. If the city continues to grow at this rate the population will rise from 11,250 to approximately 17,000 in the next 25 years (Mintier and Associates 2006);
   ● There were 4,729 housing units in Fortuna in 2005. If current growth rates continue, Fortuna will require 2,298 new housing units by 2030 (Mintier and Associates 2006);
   ● Additionally, it is projected that there will be a need for an additional 852,866 square feet of commercial, retail, and manufacturing space by 2030 (Mintier and Associates 2006).

Possible effects seen in stream conditions:

   ● The Fortuna Creeks Project found that stressful turbidity levels are reached during the rainy winter months. These high levels of turbidity, which are particularly apparent in Strongs and Rohner creeks, occur during spawning season;
   ● None of the surveyed streams met target values of pool depth;
   ● Excessive sediment in stream channels has resulted in an overall loss of spawning, rearing and feeding habitat for salmonids. High sediment levels are confirmed by embeddedness measurements in surveyed reaches.

There is concern about unrestricted stream access of livestock in agricultural areas.

Impacts from livestock grazing have been noted during stream surveys on Strongs and North Fork Strongs creeks;

Livestock grazing operations likely occur in 23% of subbasin.

Erosion related to timber harvest on unstable soils is a concern.

Timber harvest, while less of an issue than in the past, still occurred in the headwaters of all of the creeks in this subbasin from 1988 to 2005. Harvest in the headwaters of Strongs and North Fork Strongs creeks occurs on Wildcat Formation;

Wildcat Formation is largely comprised of fine sediment and is highly erosive.

There is concern about the impact of gravel mining on the mainstem Eel River.

There are eleven gravel mining sites in this subbasin that remove over 5,000 cy/yr of aggregate;

The volume of aggregate removed has decreased significantly since 1996. Before this time average volumes ranged from 500,000cy/yr to 700,000cy/yr;

The impact of previous techniques and harvest amounts are evident in the braiding of the Eel River from the mouth of Van Duzen River to Fernbridge that has occurred since 1956. A general flattening and widening of the river bed is also apparent (Humboldt County 1992);

Analysis of historic cross-sections show no significant aggradation or degradation since 1911 at Fernbridge, although there is still controversy regarding this issue (Humboldt County 1992);

The USACE has concluded that sand and gravel mining extractions are not excessive or occurring at rates that are too high to negatively impact channel morphology in the basin based on the increase of shoreline sediment. However, as bed-load data are not well known it is difficult to set adequate extraction rates and volumes;

Most of the concern in managing gravel mines is in the reconfiguration of the low flow channel. To this end, trench, alcove, or wetland pit mining are recommended over bar skimming, which has been shown to increase low flow channel width (USACOE 2003). Without the revision of extraction amounts and techniques, impacts to salmonids would be significant and would likely include loss of deep holding pools during adult migration, and loss of cover, suitable temperature, and complex habitat for juvenile salmonids.

Instream habitat conditions for salmonids are thought to be poor.

Quality pool structure is generally lacking in Middle Subbasin streams; no surveyed streams met standards for pool shelter. Pool shelter ratings ranged from fully unsuitable to somewhat unsuitable levels;

None of the surveyed streams met target values of pool depth. However, streams of the Middle Subbasin were composed of more primary pools by length than those of the Upper Subbasin;

Spawning gravels in Strongs and North Fork Strongs creeks are found in only a limited number of reaches. Additionally, crowded and superimposed redds have been observed during spawning surveys. None of the CDFG surveyed streams of the Middle Subbasin met target values for cobble embeddedness.

Recommendations


What watershed and habitat improvement activities would most likely lead toward more desirable conditions in a timely, cost effective manner?


Middle Subbasin Issues Recommendation Activities
XXX: Highest Priority
Streams Barriers to Fish Passage. Replace or modify culvert in order to meet CDFG and NOAA Fisheries fish passage guidelines. Continue efforts to identify and alleviate fish passage impediments at culverts or other road crossings. Carefully modify log debris accumulations in tributaries over time, with attention paid to resultant downstream sediment loading.    
Palmer Creek     X      
Strongs Creek     X XXX    
Rohner Creek     X      
Unnamed Tributary (Mill Creek)   X        
North Fork Strongs Creek     X X    
  Flow and Water quality. Ensure that water diversions used for domestic or irrigation purposes bypass sufficient flows to maintain all needs of fishery resources. Ensure that inadequately treated wastewater is not discharged to streams.      
Eel River   X X      
Unnamed Tributary   X        
Finch Creek   X        
Little Palmer Creek   X        
Palmer Creek   X        
Strongs Creek   X X      
Rohner Creek   X        
Unnamed tributary (Mill Creek)   X        
Jameson Creek   X        
North Fork Strongs Creek   X        
  Runoff Consider adopting a city ordinance in Fortuna to limit the amount of impervious cover in new developments. The Fortuna City Community Development Department should require development methods that incorporate on-site storm water detention and infiltration for all new developments to minimize the amount of runoff entering the drainage system. Methods include detention basins, vegetated swales, buffer strips, and other bio-retention methods.. The Fortuna City Community Development Department should require that new development not increase the existing estimated 25-year peak runoff volume from a site. Any increase in total runoff beyond the peak 25-year event resulting from new development should be retained or detained on site. Implement a channel and drainage basin maintenance program to ensure drainage channels and basin function as designed in Fortuna. Ensure that flood control projects such as culvert replacement, creek widening, creek rerouting, and stream bank stabilization do not impair anadromous salmonid migration and juvenile rearing habitat.
Strongs Creek   X X X X X
Rohner Creek   X X X X X
Unnamed tributary (Mill Creek)   X X X X X
Jameson Creek   X X X X  
North Fork Strongs Creek   X X X X  
  Erosion and Sediment Reduction Prevent livestock from accessing streams through the use of livestock management fencing. Conduct an upslope erosion inventory in order to identify and map stream bank and road-related sediment sources. Sites should be prioritized and improved. Stabilize eroding stream banks with appropriately designed structures and vegetation.    
Strongs Creek   X X X    
Rohner Creek       X    
Unnamed tributary (Mill Creek)       X    
North Fork Strongs Creek   X XXX X    
  Riparian and Instream Habitat. Consider replanting of native species, like willow, alder, redwood and Douglas fir in areas with exotic vegetation. Consider thinning hardwoods to increase growth of conifers where riparian forest is strongly dominated by hardwoods and shade canopy will not be adversely affected. Increase depth, area or shelter complexity in pools, by adding LWD or combinations of boulders and LWD. This must be done where banks are stable, or in conjunction with stream bank armor to prevent erosion. Expand spawning area by trapping and sorting spawning gravels.  
Strongs Creek   X   X X  
Unnamed tributary (Mill Creek)   X X      
North Fork Strongs Creek       X X  
  Research, and Monitoring. Monitor streams near land development activities for turbidity and drainage issues. Consistently collect water quality data, including temperature, dissolved oxygen, and water chemistry throughout the year for several years in order to accurately characterize conditions. Conduct biological sampling to determine salmonid usage and populations. Inventory habitat in urban streams. Conduct substrate sampling to determine if gravels are suitable for salmonid spawning.
Palmer Creek     X X X X
Strongs Creek   X        
Rohner Creek   X   X X X
Unnamed tributary (Mill Creek)   X   X    
Jameson Creek   X        
North Fork Strongs Creek   X        
  Education and Community Outreach. Support programs that participate in monitoring the state of urban streams, like the Fortuna high school’s Fortuna Creeks Project. Improve educational and community outreach by partnering with the City of Fortuna and through participation in events like Fortuna Creek Days. Consider a signage program for urban creeks to increase awareness of use by anadromous salmonids. Establish greenbelts along creeks in Fortuna.  
Eel River   X X X X  
Strongs Creek   X X X X  
Rohner Creek   X X X X  
Unnamed tributary (Mill Creek)   X X X X  
Jameson Creek   X X X X  
North Fork Strongs Creek   X X X X