Management Issues

Water temperatures are thought to be unsuitable for salmonids in the mainstem Big River;

There is concern that road related failures are contributing large amounts of sediments to stream channels during major storms;

Roads are thought to be a major sediment source;

There is evidence of channel narrowing and increased sediment deposition in the estuary; however, the channel could simply be recovering from the effects of extensive splash damming throughout the basin;

Estuary conditions are thought to be impaired by sediment;

Excessive amounts of fine material in streams are a concern;

A large section of the Coastal Subbasin has recently become State Park and management decisions affecting this land are in progress.

Key Findings

Flow/Water Quality

There is no temperature data for the Big River Estuary; however, it is expected that the water temperatures in the mainstem Big River quickly cool once they reach the estuary due to the marine influence;

Water temperatures at monitoring sites on the mainstem of the Big River in this subbasin were fully unsuitable in all years monitored with high diurnal fluctuations (7.9-9.9 F) and high maximum temperatures (75-76 F). This could indicate unsuitable conditions for salmonids in the mainstem upstream of the estuary;

Most of the Little North Fork Big River and tributary monitoring sites exhibited low diurnal fluctuations suggesting good shading, and/or good flow conditions and/or a tempering marine influence. This indicates suitable conditions for salmonids;

It is probable that the Little North Fork has a cooling effect on the mainstem Big River. However, the magnitude of that effect is unknown as it is dependant on the temperature differentials and flows;

There is no water chemistry data for the estuary and little data for this subbasin as a whole;

Water chemistry data available from a small stream near the estuary (R.M. 0.4), but not related to the water chemistry in the estuary itself, indicated that alkalinity and sodium appeared to be below the minimum water quality criteria;

Basic water chemistry on the mainstem Big River both upstream and downstream of the Little North Fork appear to be within applicable numeric Basin Plan water quality objectives. However, sodium at the mainstem sites upstream and downstream of the Little North Fork confluence exceeds its criteria. Additionally, copper, which is used in many herbicides, exceeds its criteria at sites upstream of the Little North Fork. However, these finding may be artifacts of the type of sampling procedure used;

Total and fecal coliform was detected on the mainstem at the sites upstream of the Little North Fork confluence. It appears as though the levels detected are not hazardous.

Fish Passage

Winter access problems for adult fish at a non-existent channel near the mouth of Manly Gulch may be stopping it from being utilized for habitat by salmonids;

Small tributaries along the estuary are blocked to fish passage by perched culverts;

Areas of dry channel found during CDFG stream surveys on eight streams may indicate fish passage problems in some tributaries.

Erosion/Sediment

Pebble counts and V* measurements in one sampled tributary (Berry Gulch) and McNeil core sediment samples in the Little North Fork indicated excessive amounts of fine material in these streams. This could indicate unsuitable conditions for salmonids.

Riparian Condition

Canopy cover was suitable for salmonids on all surveyed tributary reaches within this subbasin, but unsuitable on surveyed reaches of the mainstem Big River as expected on a larger order stream.

Instream Habitat

In the estuary, escape and ambush cover are unsuitable for salmonids;

A high incidence of shallow pools, and a lack of cover and large woody debris have contributed to a simplification of instream salmonid habitat in all nine surveyed tributary reaches;

Gravel Substrate

Cobble embeddedness values in most surveyed reaches were unsuitable for salmonid spawning success.

Refugia Areas

Salmonid habitat conditions in this subbasin on surveyed streams are generally rated as high potential refugia;

The Big River Estuary and the Little North Fork Big River provide the best salmonid refugia in this subbasin;

The estuary, mainstem Big River, and Little North Fork Big River serve as critical contributing areas, which provide critical ecological functions needed by salmonids such as providing a migration corridor or supplying high quality water.

Recommendations

Flow and Water Quality Improvement Activities

Protect instream flows in Little North Fork Big River, Railroad Gulch, and Laguna Creek to help moderate or cool the warmer mainstem Big River in the summer.

Fish Passage

Consider modifying fish passage barriers on Manly Gulch and small tributaries along the estuary;

Erosion and Sediment Delivery Reduction Activities

Continue efforts such as road improvements, and decommissioning throughout this subbasin to reduce sediment delivery to Big River and its tributaries. CDFG stream surveys indicated that nine out of eleven surveyed tributaries in this subbasin had road sediment inventory and control as a top tier tributary recommendation;

Continue to support and encourage current and future road management programs undertaken by California State Parks;

California State Parks should follow the recommendations of CGS (2004) in treating identified sediment sources on roads and road crossings within Big River State Park;

All roads within Big River State Park and their associated watercourse crossings required for public safety, existing easements, future restoration effort success, and public access must be maintained to high standards (CGS 2004);

Encourage the use of appropriate Best Management Practices for all land use and development activities to minimize erosion and sediment delivery to streams. For example, low impact yarding systems should be used in any timber harvest operations on steep and unstable slopes to reduce soil compaction, surface disturbance, and resultant sediment yield;

California Department of Parks should consult with appropriate resource professionals to assist in transitioning industrial timberlands on the Big River State Park to self-sustaining forest (CGS 2004).

Riparian and Instream Habitat Improvement Activities

Where feasible, add LWD to develop habitat diversity in the main channel and to increase shelter complexity for salmonids. CDFG stream surveys indicated that all nine surveyed tributaries and the mainstem Big River have increase shelter as a top tier tributary recommendation;

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

Ensure that this high quality habitat is protected from degradation. The highest stream reach conditions as evaluated by the stream reach EMDS and refugia analysis were found in the Big River Estuary, mainstem Big River, Little North Fork Big River, Railroad Gulch, East Branch Little North Fork Big River, Berry Gulch Tributary, and Rocky, Thompson, and Berry gulches.

Education, Research, and Monitoring Activities

Conduct surveys of ten small tributaries entering the estuary through blocked culverts in the Big River State Park to determine if they provide salmonid habitat;

Establish monitoring stations to track instream sediment along the estuary;

Continue water temperature monitoring at current locations where high temperatures have been detected on the mainstem Big River;

Assess water temperature and dissolved oxygen in the estuary as there is currently no data on these indicators;

Establish long-term water chemistry monitoring stations in the lower mainstem Big River. If there are indications of problems, monitoring should be implemented in tributaries as necessary to determine the source of the problem.