"For salmon populations barely hanging on in a system where sediment can affect volume of holding pools and quality of spawning gravels, any sediment produced cannot benefit salmon habitats. It can only degrade those habitats..." (Harr, 1992)
Introduction
Over the last three decades, various state and federal fisheries and watershed studies on the South Fork Trinity River system have identified a variety of resource problems leading to currently degraded conditions. Many of these researchers and land managers have also proposed solutions to reverse the decline in anadromous fisheries. Some of these recommendations have been successfully implemented, while many others have not.
The USFS has identified both protection and restoration as key elements in the basin's recovery: "The most significant challenge facing fisheries and watershed specialists during the next 15 to 20 years is the protection, maintenance and improvement of watershed conditions and viable fish habitat to ensure continued perpetuation of anadromous and resident fish stocks in the basin" (Haskins and Irizarry, 1988, p. 37).
In its ground breaking erosion and sedimentation study of the South Fork, the California Department of Water Resources (CDWR, 1979) concluded that protection of the watershed must come from three (3) actions:
1. Rehabilitation of damaged areas producing high sediment yields,
2. Recognition and avoidance of land management on potentially hazardous areas in the watershed (through data collection and geologic investigations), and
3. Prevention of further watershed damage through changes in forest practice rules and land use practices.
The objective of these actions was protect and restore fisheries through "implement[ing] watershed management and land use regulations to save the soil resources and greatly reduce sediment inflow to the system" (CDWR, 1977).
Coordination Between Agencies and Between Agencies and Landowners
There has often been a lack of communication and coordination between resource agencies, and between agencies and private landowners in the basin. This has resulted in poor dissemination of resource information (forest, fisheries and wildlife), research and monitoring results, and best management practices most suitable to protecting on-site and downstream resources.
1. The South Fork Trinity River CRMP (see above) should take a leading role in organizing and directing South Fork Trinity River watershed and fisheries restoration, and should facilitate improvements in interagency and agency-landowner communication and coordination on matters related to restoration, and land and resource management issues.
2. In other matters related to the South Fork Trinity River and its fisheries resources, the U.S. Forest Service and state regulatory agencies need to develop more extensive avenues of communication and an improved, cooperative working relationship (CDWR, 1979).
A. Annual meetings should be organized to disperse fisheries and watershed data and to discuss monitoring needs as well as restoration and land management plans (CDWR, 1979). Private landowners and land managers should be encouraged to participate in these exchanges.
B. A comprehensive and coordinated basin-wide management program should be implemented immediately through a genuine and cooperative commitment by both the U.S. Forest Service (Six Rivers and Shasta-Trinity National Forests) and the State of California (California Departments of Forestry and Fire Protection, Fish and Game (CDWR, 1977). There must be an improved mechanism for discussing and reviewing best management practices for this sensitive basin, and for avoiding or mitigating the effects of proposed public and private land use activities on streams and fish.
Managing Unstable or "Sensitive" Terrain
A. Mapping information needed
The Department of Water Resources has identified poor land use practices, primarily on sensitive or unstable private industrial forest lands, as perhaps the most influential factor resulting in degraded watershed conditions in the South Fork Trinity River. This situation has been brought about largely through early, unregulated harvesting, and more recently by continued abandonment of forest road systems when harvests are complete.
1. More and better resource information is needed to make wise land use decisions in the South Fork Trinity River basin (CDWR, 1979). New and revised mapping information is needed to assist in future land use planning, on both public and private lands. This includes:
-Timber location, site quality mapping and harvesting history (update of CDWR, 1979), (this information will provide planners and professionals with a view of the expected location of future land use activities and potential impacts in watersheds of concern)
-Fishery habitat mapping showing past, present and potential utilization by salmonids,
-Water users mapping showing intake locations, volumes and discharges, and
-Large scale land use mapping, showing terrain sensitivity, slope stability, inner gorge locations, maintained and abandoned road networks, and harvest history, with an overlay of existing timber resources.
B. Defining, mapping and managing "sensitive lands":
"Defining sensitive lands, their relative hazard and appropriate management level is of supreme importance in watershed management [in the South Fork Trinity River basin]" (Haskins, 1983, p 33).
It was clearly recognized in the 1970s that there was a need to formally delineate and map landslide hazard zones and terrain sensitivity on South Fork Mountain (MacCleery, 1974; Kojan 1972). Additional protection for federally managed lands is pending under the South Fork's key-watershed status. It is very important that large-scale mapping be similarly completed for private lands on South Fork Mountain, to help guide future land use planning, and that special protection be afforded sensitive slopes and sub-watersheds.
1. Sensitive watershed areas, such as streams, erodible soils, inner gorges and unstable slopes, should be delineated and management specifically geared to these conditions (Haskins and Irizarry, 1988).
A. Slopes and subwatersheds tributary to the main stem South Fork Trinity River should be recognized as a sensitive watershed area (re: California Board of Forestry Rules), with unique land and resource management needs and requirements.
B. Stable and unstable watersheds and terrain locations need to be identified and mapped covering all TPZ land in the South Fork Trinity River watershed. This effort has already been undertaken for USFS lands.
C. Special operating regulations (silvicultural restrictions, roading practices, etc), aimed at prevention of erosion and sediment yield, need to be developed and implemented for identified sensitive watersheds and terrain areas.
2. To avoid repeating the devastating land use impacts that were so prevalent following the 1964 storm, preventive measures have since been employed on Forest Service lands in the South Fork Trinity River basin (Haskins, 1981). None of these, or equivalent, preventive measures have been adopted for use on private lands in the basin, but their incorporation in California forest practice regulations for this sensitive watershed is strongly recommended.
A. Map inner gorges and active/dormant landslide areas, defining high hazard areas for avoidance during timber harvesting and road building operations.
B. Design streamside management zones to include the full length of inner gorge slopes, or greater, and severely restrict harvesting and management (stressing vegetation retention) in these potentially unstable areas.
C. Restrict harvesting and road construction within or adjacent to the primary inner gorge along the South Fork Trinity River.
D. Keep the number of stream crossings and length of roads to an absolute minimum within tributary inner gorge zones. Crossing sites should be selected or approved by a geologist. Culverts should be oversized (exceeding the 50-year flood capacity) and trash racks, drop inlets and outlet structures should be used.
E. Cumulative watershed analyses should be performed for subwatersheds and management should be restricted to acceptable levels based on a measure of past sub-watershed disturbance and channel degradation. This will require the identification, analysis and possible deferment, reduction or modification of future forest management activities in highly erodible or unstable terrain types.
F. Planting landslides and unstable areas.
3. It is highly recommended that the following, or similar, land use practices, be adopted as "best management practices" for operations on "sensitive" forest lands in the South Fork Trinity River basin, especially including slopes and sub-watershed tributaries originating on South Fork Mountain.
A. A light selection or salvage may be considered appropriate in some of the more stable inner gorge streamside management zones, but a geologist should first thoroughly evaluate each proposal (Haskins et al., 1980). Sensitive or potentially unstable inner gorge slopes should be deferred from harvest and each may ultimately be considered "unsuitable" for timber management and road building.
B. Non-inner gorge streams should have a 100-150 foot wide stream management zone. Limited selective harvesting may be possible in this zone, but burning and equipment use is to be avoided (Haskins et al., 1980).
C. Improved regulations are needed which limit or prohibit the removal of timber stands on certain slopes which drain directly onto steep, unstable inner gorge slopes. Any harvesting or road (or landing) construction proposal for these "peripheral zone" areas (slopes immediately adjacent inner gorges) should be field inspected by a geologist prior to plan layout for harvesting or road building. Selection or other partial cutting methods (as opposed to clearcutting) may be most appropriate for slopes immediately draining onto these streamside inner gorges. Special road loaction and construction techniques may also be needed to avoid downslope effects.
Road Planning, Construction, Maintenance and Closure
Roads are the largest source of persistent and continuing accelerated erosion in the South Fork watershed (CDWR, 1979). They are also perhaps the greatest potential future sediment source and represent a serious threat to the protection and recovery of anadromous fisheries in the South Fork Trinity River. Roads in the basin consist of both maintained routes (most of which are logging roads) as well as hundreds of miles of abandoned roads which are no longer being maintained.
1. Establish desired future conditions: Initially, it is important to conduct an interdisciplinary review of all private and public forest roads in the basin (both active and abandoned), and to determine the desired future condition of the watershed road network, considering both resource protection issues and forest management needs.
2. Road network planning: A long term integrated road network consisting of a permanent access system confined to stable terrain, with temporary roads accessing adjacent timber sites should be planned and implemented. This is especially important on South Fork Mountain, where roads have been implicated in dramatically accelerated erosion and sedimentation (CDWR, 1979; MacCleery, 1974; Haskins, 1980).
3. Inventory and assess all existing roads: All existing, driveable roads in the watershed should be assessed and prioritized for upgrading, relocation or closure based on various factors, including their status in the planned, long-term road network (see above) and their potential for future erosion and seidment yield (USFS, 1992). Reasonable goals and factors to consider in this inventory and planning effort include:
A. establishing acceptable road densities for sub-watershed areas based on terrain stability and sensitivity to disturbance, while striving for lower road densities and eliminating unnecessary or damaging roads,
B. inventorying and upgrading all stream crossings for roads which are to remain as a part of the permanent road system to handle at least the 50-year storm runoff, and the 100-year flows for South Fork Mountain (the USFS is currently considering 150-year capacity for stream crossings in "key watersheds," including most of the South Fork Trinity River),
C. designing all new or rebuilt stream crossings with natural stream bottoms (using bridges or arch culverts), especially where fish have, or could have, access, or where floatable debris could plug culverts, and
D. obliterating (decommissioning) roads that are not to be part of the desired future transportation system.
4. Inventory and assess all abandoned roads: A complete air photo and field inventory of abandoned roads is crucial and should be conducted for all public and private land holdings in the South Fork watershed, especially lands on South Fork Mountain. Most abandoned roads on USFS lands have already been inventoried, assessed and prescribed for preventive treatment. Undersized culverts and log crossings which have been left in-place on hundreds of miles of abandoned road in the basin are a great threat to downstream fisheries resources. These crossings are destined to eventually fail and deliver sediment to downstream areas, and should be quickly located, inventoried and preventively treated. All assessments of abandoned roads should include:
A. an inventory and assessment of abandoned (unmaintained) drainage facilities,
B. an inventory and assessment of road and landing fills and sidecast slopes which need to be removed before they fail and deliver sediment to stream channels, and
C. an inventory and assessment of all existing roads which cross inner gorge slopes of the main stem South Fork Trinity River and its incised tributary streams. Chapter 16 continued