Issues

Key salmonid fishery issues of concern identified for the Redwood Creek estuary include:

Channel modifications from the flood control levee system have likely had the most impacts to the physical form and alterations of natural processes that drive the estuarine ecosystem;

The estuary is particularly susceptible to watershed cumulative effects;

Juvenile salmonid rearing success is impaired by estuarine habitat conditions;

Estuary habitat improvement projects have been proposed.

Findings

Channel modifications from the flood control levee system have likely had the most impacts to the physical form and alterations of natural processes that drive the estuarine ecosystem:

The affects of levees exacerbate sediment accumulations and a contribute to the loss of tidal connectivity to slough channels and a reduction in tidal prism;

Removal of riparian trees for pasture development and levee construction caused the loss of benefits from the riparian forests;

Riparian vegetation is periodically removed from the estuary channel as part of a levee maintenance procedure.

The estuary is particularly susceptible to watershed cumulative effects:

The low gradient, depositional reach of Redwood Creek in the Estuary Subbasin accumulates watershed products delivered from upstream reaches;

Juvenile salmonids that reside and pass through the estuary during spring and early summer during seaward migrations find favorable water quality conditions for rearing and may acclimate to changes in salinity and temperature;

Much of the water quality and sediment characteristics of the estuary are related to upstream watershed conditions;

These include relatively warm water inputs and high levels of sediment delivery.

Juvenile salmonid rearing success is impaired by estuarine habitat conditions;

The fish rearing area of the Redwood Creek estuary/lagoon has been reduced by 50 to 75 percent;

Survivorship is very low (estimates of 7-15%) for juvenile Chinook and steelhead that rear in the lagoon through the summer;

The estuary/lagoon once supported an abundant, year round population of coastal cutthroat trout. At present, only a few coastal cutthroat are found during fish surveys;

The estuarine channels are shallower compared to historic conditions;

Habitat shelter complexity is low due to a lack of riparian vegetation and LWD;

Dissolved oxygen levels can be at stressful or lethal levels in the slough channels;

Estuary habitat improvement projects have been proposed:

A large amount of work has been done by RNSP, private landowners, public agencies, and interested parties to develop alternatives to improve habitat conditions in the estuary/lagoon, while protecting Highway 101 and the Town of Orick. These include various levee setback alternatives and shortening the extent of the levees to exclude the lowermost channel reach;

A properly functioning riparian zone is needed to improve the estuarine ecosystem and increase the estuary’s value as salmonid habitat.

Recommendations

A great amount of work has been done by RNSP, private landowners, public agencies, and interested parties to develop alternatives to improve habitat conditions in the estuary/lagoon, while protecting Highway 101 and the Town of Orick. These include widening the levees and shortening the extent of the levees to exclude the lowermost channel reach.

We do feel that the use of levee set backs, reconfiguration, or levee removal strategies to develop a wider flood plain that restores natural sinuosity, improves connectivity with sloughs and adjacent wetlands, and the allows the development of an effective zone of riparian vegetation will contribute to a large improvement to the estuarine ecosystem. The following recommendations are provided to help guide the goals and objectives of a project to benefit the estuarine ecosystem and in turn increase the production and carrying capacity of anadromous salmonids in the estuary/lagoon.

Flow and Water Quality Improvement Activities:

Increase tidal prism by restoring tidal and riverine flow and connectivity between the main channel and slough channels;

Increase depth and tidal exchange at the confluence of North Slough channel;

Increase circulation between the lagoon, Strawberry Creek and sloughs to help mix water and increase dissolved oxygen levels;

Prevent or reduce cattle waste from entering stream and slough channels;

Develop a shade corridor of riparian trees along main channel to help cool water;

Land managers should work maintain and/or establish adequate streamside protection zones to reduce solar radiation and moderate air temperatures into Redwood Creek and its tributaries throughout the Redwood Creek basin;

The goal of any controlled breech project must be to maintain the volume in the lagoon to best support the anadromous fisheries;

Digging of any artificial channel through the beach sand berm that would result in an uncontrolled breech should be discouraged;

Any controlled breech should be performed as an option and in coordination with the expert judgment of RNSP staff and CDFG to preserve natural resources.

Erosion and Sediment Delivery Reduction Activities:

Reduce inputs of sands by tidal currents to the embayment and North Slough by modifying levee configuration or removing levees altogether;

Use levee set back, reconfiguration or removal strategies to achieve more natural flood plain characteristics;

Land managers should continue their efforts such as road improvements, good maintenance, and decommissioning and other erosion control practices associated with all land use activities throughout the basin to reduce sediment delivery to lowermost Redwood Creek and the estuary.

Riparian and Instream Habitat Improvement Activities:

A properly functioning riparian zone is needed to improve the estuarine ecosystem and increase the estuary’s value as salmonid habitat;

Where feasible, develop or improve riparian vegetation function along the banks of Redwood Creek, Strawberry Creek, and slough channels;

Work to restore natural drainage patterns within adjacent wetlands and the subbasin;

Increase off-channel and rearing habitat by improving conditions of sloughs and tributaries (Strawberry, Dorrance and Sand Cache creeks);

Increase depth and complexity in the main channel and slough channels;

Where feasible add LWD to increase salmonid shelter complexity;

Leave large wood in estuarine channels, on the beach, and on stream banks for potential recruitment into the estuary;

Relocate drift logs that block tidal connectivity between the embayment and the North Slough channels;

Re-establish a corridor of riparian vegetation to lower Strawberry Creek and restore riparian function in areas where vegetation removal or significant cattle impacts have been noted. This may require temporary fencing the riparian zone to prevent cattle and deer from grazing on seedlings and trampling growing trees.

Education, Research, and Monitoring Activities:

Work should continue by Redwood National and State Parks (RNSP), private landowners, agencies, and interested parties to improve habitat conditions of the estuary by modifying the levees system while protecting Highway 101 and the town of Orick;

RNSP, DFG, RWQCB should continue existing monitoring of anadromous salmonid populations and expand to include some winter and early spring sampling;

Water temperature and dissolved oxygen monitoring in the lagoon and sloughs should continue. Some dissolved oxygen measurements should be collected just before sunrise to capture lowest diurnal levels;

Monitoring water quality in the lagoon should be expanded to include nutrient levels (ammonia, nitrates, nitrates) that may be elevated from runoff from cattle pastures;

Work with USACE, Redwood National and State Parks, and Humboldt County Department of Public Works to modify levees and levee maintenance manuals to be consistent with habitat requirements of salmonids and a properly functioning estuarine ecosystem.