"...A comprehensive watershed rehabilitation program is essential and required if in-stream habitat is to be improved." (Frederiksen, Kamine and Associates, 1980)
Since the mid 1960's, professionals working within the South Fork basin have recognized the damaging impacts which have occurred as a result of certain land use practices, as well as, for the need to modify land use practices and perform preventative erosion control work to minimize sediment production and damage to fisheries habitat (Rowland, 1966; Wahrhaftig and Curry, 1967; USSCS, 1972; MacCleery, 1974; Knott, 1974; LaFaunce, 1975; CDWR, 1979, 1982a, 1982b; Haskins, et. al., 1980; Frederiksen, Kamine and Associates, 1980; Irizarry, et. al., 1985).
Up until the mid 1980's, efforts to perform erosion control or erosion prevention were largely centered around defining sensitive and potentially unstable hillslopes, and implementing avoidance or low levels of disturbance strategies. Actual erosion control work was frequently perceived to be and conducted either as an aspect of annual road maintenance activities, or as part of road reconstruction activities following larger return interval storms and floods. All these earlier activities have contributed to our understanding of which practices, and where various land use practices, can contribute to cumulative watershed impacts. However, the rate at which on-going timber harvesting and road construction was occurring far exceeded our ability to incorporate necessary reform into land management schemes which recognized the importance of protecting water quality.
Numerous authors have suggested relevant strategies, watershed rehabilitation needs, protective land use changes and prioritized approaches for conducting fisheries and watershed rehabilitation in the South Fork Trinity River basin. Several noteworthy sources of past restoration suggestions, including those of the Department of Water Resources (1979, 1982), the Model Steelhead Demonstration Project (Irizarry, et. al., 1985) and various reports and findings of the U.S. Forest Service, follow. A minority of these suggestions have actually been implemented.
All improvement projects for the South Fork Trinity River basin need to be prioritized. The location of future work projects must be based on basin-wide needs, the probability of success, and cost-effectiveness (Haskins and Irizarry, 1988). Roads which are no longer needed, or which pose a threat to riparian or aquatic resources, should be "put-to-bed." Other roads should be "erosion-proofed" so they are no longer a threat to downstream areas (CDWR, 1982b). Forest areas which will not revegetate should not be cut, and a comprehensive reforestation program should be implemented for areas which are not currently stocked (CDWR, 1982b). To address the cause of the sedimentation problem, watershed rehabilitation of the hillslopes and stream channels should also be undertaken (CDWR, 1982b).
A streambank and landslide stabilization feasibility program should be initiated (CDWR, 1982b). A large number of landslides in the basin have been caused, accelerated or reactivated by human activity. Control can be expensive and difficult, so it has been recommended that each case be evaluated by specialists. It has also been recognized that it will be "infeasible or impractical to attempt to stabilize some of the worst sediment sources within the watershed, such as the large landslides within the Grouse and Pelletreau drainages or the aggraded wedge of sediment in the lower main stem of the South Fork" (Irizarry, et. al., 1985).
Some of the problems in the watershed are beyond the breadth of what is feasible or practical to accomplish (Haskins and Irizarry, 1988). For example, most large landslides in the basin are too large to stabilize, and those that are technically feasible to control are economically infeasible. Landslide prevention has always been recognized as more effective and cost-effective than structural control measures. Potentially successful landslide control measures are typically difficult and expensive to employ, but may be locally effective. Such techniques include revegetation and replanting, drainage diversion, horizontal drains, rip-rapping and buttressing (CDWR, 1979). The practice of planting existing landslides and landslide scars with deep rooted woody plants should be investigated and locally employed (MacCleery, 1974; Mike Furniss, personal communication). The feasibility and utility of replanting the banks of gutted stream channels as a rehabilitation and erosion prevention measure should also be evaluated (MacCleery, 1974).
Habitat improvement in the main stem is considered infeasible due to the mobile bed material (Haskins and Irizarry, 1988). It has been suggested that studies be initiated to determine the feasibility of building sediment traps on high yield tributary streams, such as Grouse and Pelletreau Creeks, to keep excess sediment from entering the main stem (CDWR, 1982b). Although expensive, such treatment could accelerate natural sediment removal and recovery of the lower main stem of the South Fork. Large scale excavation of sediment from portions of the Hyampom Valley may also be feasible and should be investigated as one of the few tools available for restoration of the main stem South Fork Trinity River.
Structural habitat improvement in tributary stream channels of the South Fork Trinity River has received considerable funding in recent years. However, it has been recognized by all parties that the success of in-stream enhancement measures in tributary streams will be largely dependent on substantial reduction of high sediment yields from upland areas in the basin (CDWR, 1982b). "It is infeasible to attempt to stabilize a problem in the lower portion of a sub-watershed if a persistent "un-treatable" problem exists above it" (Irizarry, et. al., 1985). For this reason, "... improving fish habitat by constructing [structures] gives only short term benefits, at best" (USDI, 1990), and should be cautiously applied.
Stream channels can also be treated by judicious removal of debris dams, slash and barriers, deflection of flow away from undercut banks and landslides, gravel removal from aggraded reaches, building sediment retention structures, planting, and rip-rapping the toes of slides and sensitive banks (CDWR, 1979). Before employing any of these measures, their utility and cost-effectiveness should be thoroughly reviewed.
In recent years, watershed staff from the Hayfork and Yolla Bolla Ranger Districts of Shasta Trinity National Forest, and Six Rivers National Forest (SO Office) have conducted watershed inventories on large portions of the lands under their jurisdiction in order to identify potential erosion problems which could lead to downstream sedimentation in the South Fork and its tributaries (Plate 1). The inventory work has been funded either through the Trinity River Fish and Wildlife Restoration Program (TRFWRF), or through USFS budget sources such as WIN (Watershed Improvement Needs Program) and KV monies (Knudsen-Vandenberg Act Program). Most inventories were completed from approximately 1988 to 1991 (several more recent assessments have been completed, but are not shown on Plate 1).
Status of inventories
The USFS has divided the South Fork basin into 21 sub-basins for watershed inventory and management purposes (Figure 11-1). These include three sub-basins in downstream areas on Six Rivers National Forest, five sub-basins in the headwater portions of the South Fork and Hayfork Creek watersheds on the Yolla Bolla Ranger District, and 13 sub-basins on the Hayfork Ranger District. Federal lands in all but 6 of the sub-basins have been inventoried for potential erosion problems. Sub-basins not inventoried in large part, or in full, include:
1. Lower South Fork (SRNF)
2. South Fork below Hyampom (STNF)
3. Big Creek near Hayfork (STNF)
4. Middle Hayfork Creek (STNF)
5. East Fork Hayfork Creek (STNF)
6. Uppermost South Fork (STNF)
Figure 11-1. Twenty-one sub-basins of the South Fork Trinity River watershed used for watershed inventories. NOT AVAILABLE IN ELECTRONIC FORMAT
Watershed inventories in the above six sub-basins or compartments were judged to be of lower priority based on either low road densities or being underlain by a high percent of inherently stable bedrock and soil types (John Veevaert, personal communication). The USFS indicated these lower priority compartments would be inventoried as funds become available.
Within the South Fork watershed, approximately 200 mi2, or 21% of the total land base is privately owned. The majority of the private land is located west of the main stem of the South Fork on the highly erodible and unstable terrain of South Fork Mountain (MacCleery, 1974; Kojan, 1976; CDWR, 1979 & 1992; Haskins, et. al., 1980), and is managed for commercial timber production. A sizeable but smaller tract of privately managed land surrounds the community of Hayfork and is mainly managed for ranch, agricultural and residential purposes. Elsewhere, smaller tracts of private lands are scattered throughout the South Fork watershed.
Private, industrial forest lands in the Grouse Creek basin have been inventoried by Six Rivers National Forest staff as part of a cooperative agreement between public and private landowners. However, no private lands within or adjacent to Shasta-Trinity National Forest have been inventoried for on-going and potential erosion problems. In 1990, formal request by the USFS for access to conduct watershed inventories were denied, presumably due to a lack of interest or unwillingness to permit USFS staff on private lands (USFS files, Hayfork Ranger District).
Evaluation of inventory work
In reviewing watershed assessment data and reports prepared by USFS personnel, and based on our own field reconnaissance and numerous discussions with knowledgeable workers in the South Fork watershed, several observations concerning the assessments are noteworthy.
1. Inventories of roads and slopes for treatable erosion problems on the Hayfork and Yolla Bolla Ranger Districts were largely completed by temporary personnel with minimal technical training and little past experience in related work (John Veevaert and George Cruz, 1992, personal communication). Field crews who gained valuable experience during a season of mapping were seldom available to perform the same work the next season for a variety of reasons. As a result, the quality of watershed inventories and the associated recommendations have been highly variable, and were often less than desired. It is widely accepted in the professional community that trained geomorphologists, watershed scientists, hydrologists, and geologists must conduct initial field studies in order to obtain complete, and reproducible watershed inventories (Harr and Nichols, 1993; Pacific Rivers Council, 1992; Weaver, et. al., 1987; USNPS, 1981).
2. Watershed assessments in both the Yolla Bolla and Hayfork Ranger Districts mainly consisted of either culvert inventories at stream crossings, or stream channel surveys intended to locate reaches experiencing channel bank erosion and loss of riparian canopy (USFS, 1990g,h; 1991b,c,d; 1992b,c; 1993a,b,c,d). As a result, assessments from both districts were very weak, or sometimes lacking in their identification, analysis and recommendations for treatment of unstable areas, particularly along landings, road fills and within timber harvest units.
According to STNF professional staff, the emphasis on culverts and stream channels was influenced by several factors. 1) Haskins (1981) listed poorly designed and maintained stream crossings as one of several major causes of sediment production on South Fork Mountain. 2) Most areas within the Hayfork sub-basin are underlain by relatively stable bedrock not prone to large-scale mass wasting. 3) Many of the roads in the inventoried compartments experienced larger storms in 1974 and 1986 without widespread evidence of mass wasting. 4) Budget constraints on funding levels for the South Fork necessitated concentrating on relatively more straight forward culvert assessments as opposed to identifying and classifying more complex mass movement features. 5) Professional staff on both Districts correctly realized most temporary staff conducting field assessments were not qualified to identify and evaluate landslide features nor their risk of failure. 6) Professional staff did not have available time to accompany or thoroughly field-check all inventoried segments of roads for quality of observations and conclusions, and 7) Staff felt many mass movement features could not be economically treated to prevent erosion in light of existing Forest Service road maintenance budgets.
Comprehensive mass movement inventories in the Hayfork sub-basin at this time may not derive huge paybacks from a cost-benefit perspective. However, given the intent of the Report of the Forest Ecosystem Management Assessment Team (FEMAT, 1993), it seems imperative to conduct complete mass movement inventories in all Key Watersheds and Refugia sub-watersheds.
Several factors also contributed to the decision to focus restoration inventories in stream channels. Many hundreds of miles of stream channels were impacted by large wildland fires between 1987 and 1989. As a result of the fires, and on-going, in-stream fisheries habitat surveys and improvement projects conducted since 1985, USFS staff and large CCC labor crews had observed frequent existing and potential sediment sources adjacent to stream channels. Many of these features were perceived as potentially treatable or correctable erosional problems. It was also recognized that stream channels frequently exhibited impacts to fisheries habitat associated with past and on-going management activities, and these too were perceived as treatable.
3. Many inspected stream crossings on Shasta Trinity National Forest lands are well constructed and pose little risk of sizeable erosion and sediment yield. However, at those stream crossing sites where the risk was unclear or more difficult to determine, follow-up field verification by Forest Service professional staff occurred only if temporary field staff recognized and red flagged a potential risk for road or resource degradation. This communication gap, coupled with the inexperience of field crews, and the limited available time by overcommitted professional staff on the Districts, prevented the thorough field checking of many potential erosion sites described in the field data sheets and watershed assessment reports. It is estimated that on the Hayfork and Yolla Bolla Districts approximately 50% and 35%, respectively, of the inventoried sites received follow-up professional oversight (STNF, personal communication).
4. Watershed assessment activities conducted in the Grouse and Madden Creek basins on Six Rivers National Forest were more thorough, but considerably more costly. Field inventories were carried out by geologists and geomorphologists, and both fluvial (stream crossing) and mass movement sources of past and future erosion were inventoried. However, reports of potential work sites and recommended treatments were not available to us at the time of this evaluation. Instead, Six Rivers has prepared a number of annual reports detailing progress to date, as well as results of the "sediment budget" studies (Kelsey, et. al., 1989).
5. Watershed assessments and erosion inventories on both Six Rivers and Shasta-Trinity National Forests were concentrated along major and secondary forest roads. This included many dead-end roads which were temporarily closed by gates or large berms. Roads which were extensively abandoned and overgrown with vegetation, and some currently unmaintained roads, were not inventoried by field crews. It is estimated that 10% to 20% of the roads in any sub-watershed may have not been mapped (Mike Furniss and John Veevaert, 1992, personal communication). Depending on the age of road construction, and the storm history since road abandonment occurred, many of these roads could pose considerable risk of sediment production (Harr and Nichols, 1993; Weaver, et. al., 1987; Peak Northwest, Inc., 1986; Weaver, et. al., 1981). Chapter 11 continued