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Putting Humpty Dumpty Together Again

Timber harvesting and surface mining can severely degrade and damage watersheds. Removal of trees and construction of haul roads, skid trails, and landings associated with timber harvesting operations, for example, often cause massive erosion and slope failures. This erosion and mass wasting deliver large quantities of sediment and debris to streams and rivers. Sedimentation in turn degrades water quality, destroys aquatic habitat, and results in flooding. Sediment is the number one pollutant in our nation's waterways in terms of magnitude and adverse impact. According to a recent National Water Quality inventory conducted by US Environmental Protection Agency siltation and nutrients (e.g., phosphorus) from erosion impair more miles of rivers and streams than any other pollutant.

The influence of haul roads and skid trails is particularly pernicious because they are not merely sources of sediment but also tend to destabilize other parts of a watershed by deranging hillside hydrology. Roads concentrate and channel runoff, capture subsurface seepage and convert it to overland flow, and transfer runoff across drainage divides. Stream crossings on earthen fills and culverts are vulnerable to washout particularly if the culvert becomes plugged with slash and other debris from a logging operation.

Accordingly, one of the keys to successful watershed repair and restoration is to decommission abandoned haul roads and skid trails. Decommissioning does not mean simply constructing waterbars, dips, and cross-road drains. Waterbars often cause unintended problems of their own. Instead a more comprehensive treatment is required that entails modification of the road prism with at least partial restoration of original hill slope contours and removal of road fill and old log landings from drainages.

Watershed repair and restoration techniques can perhaps be appreciated best by examining some case studies. Two notable efforts are briefly described herein, namely, the watershed rehabilitation work in Redwood National Park and Whiskeytown National Recreational Area respectively.

Redwood National Park

The creation and later expansion of Redwood National Park in 1978 resulted in the acquisition of approximately 48,000 acres of cutover timberlands. These cut-over lands, representing nearly 45 percent of the 106,000-acre national park, were intensely modified by logging activities, including the construction of approximately 300 miles of haul roads and 3,500 miles of tractor trails.

In addition to their profound scenic impact, past logging activities in the region had caused soil compaction, loss of topsoil, and massive changes in small drainages or watersheds tributary to Redwood Creek. Logging activities also produced cumulative downstream impacts such as increased bank erosion, siltation, and streamside landslides. The latter impacts directly threatened the superb groves of tall trees growing on alluvial flats along Redwood Creek.

Problems associated with these cut-over lands were addressed in legislation which expanded the Park. Section 101 of Public Law 95-20 authorized $33 million to be appropriated to carry out rehabilitation provisions of the act. This mandate was entrusted to the National Park Service who developed an in-house expertise and rehabilitation program relatively quickly. In order to test and evaluate rehabilitation techniques, the Park Service began five projects in the Redwood Creek watershed in 1978, and has initiated new projects, in succeeding years.

As a result of these projects a visitor to the Park now has a rare opportunity to observe at first hand some innovative and effective erosion control and land restoration techniques. The best place to begin a rehabilitation tour is at the Park headquarters in Orick. Information is available there describing the restoration program and the location of various rehabilitation sites and projects.

The Park Service experimented with a variety of land restoration tactics and techniques. A decision was made early on to focus on the source of the problem, namely increased flows of sediment, debris, water coming from damaged, tributary watersheds rather than try to control bank erosion and sedimentation in the main stem of Redwood Creek itself. Much of the initial restoration work was labor intensive and employed widespread use of shovels, pickaxes, and portable chainsaws. Considerable effort was expended to restore and repair deranged hillside hydrology. Large erosion gullies had developed in many of the watersheds because of inappropriate concentration and diversion of surface and subsurface water by roads and skid trails during logging operations. Revegetation treatments and soil bioengineering methods were employed to control erosion.

Heavy equipment such as bulldozers, hydraulic excavators, and draglines were reserved mainly for working on the roads. Skillful operators where able to rip (decompact) haul road surfaces, reshape road prisms, and pull eroding earthen fills out of stream draws with such equipment. This process, sometimes referred to as putting a road to bed, generally restores the original contours of the land and helps with subsequent revegetation. Currently, a majority of this work is performed by retrained and highly skilled heavy equipment operators.

Several interesting findings emerged from these restoration projects in the Park. Labor intensive treatments for controlling erosion and reestablishing vegetation were used primarily in the early stages. The single most effective surface treatment technique for erosion control was the use of heavy mulching with long straw mulch. Evaluation of these labor intensive treatments ultimately led to their reduced use in later stages of the restoration work. Instead heavy equipment work became an increasingly important component of watershed rehabilitation activities. Greater emphasis was placed on the use of heavy machinery for contour restoration, reconstruction of drainages, and removal of earth fills from stream draws. Less emphasis was devoted to hand labor practices designed to slow sheet and rill erosion on hillsides. It quickly became evident, in other words, that a landscape damaged by heavy machinery requires the use of heavy machinery for its effective repair. The heavy equipment work was by far the most cost effective in terms of dollars spent per unit of soil saved or held in place. It was also apparent that restoration work itself can cause some soil erosion and disruption of hillside hydrology, particularly when using heavy machinery. In order to minimize the impact of this secondary disruption it is important to do the restoration work as soon as possible.

The watershed rehabilitation work in the Park has clearly helped to restore these lands to their former equilibrium and grandeur. Redwood National Park provides an ideal showcase for a variety of ecosystem restoration methods. All the governments horses (mules were actually used at one rehabilitation site) and men successfully put Humpty Dumpty together again.

Whiskeytown National Recreational Area

The Whiskeytown National Recreational Area is located eight miles west of Redding, California, along the Highway 299 corridor in a region of coarse grained, granitic soils that are particularly susceptible to erosion when disturbed or denuded. Prior timber harvesting operations left behind many abandoned skid trails, haul roads, and fill crossings that were eroding badly and adversely affecting hillside hydrology. These impacts resulted in massive siltation of local streams and devastation of salmonid fisheries. In response to this threat, a treatment demonstration project was established in the Clear Creek watershed an important sub-watershed and tributary in the Sacramento River basin.

The Whiskeytown National Recreational Area requested help from Redwood National Park and other experts for developing their long-term restoration plan. John McCullah, Principal, of Salix Applied Earthcare, a firm specializing in erosion control and watershed restoration, was asked to assist in this effort. He was charged with helping the Park to develop a restoration protocol, including road erosion inventories, road treatment strategies, and effectiveness monitoring.

McCullah was selected because of his prior experience in directing the Grass Valley Creek Watershed Restoration Project a multi-agency effort aimed at stopping the massive discharges of sediment to the Trinity River from this highly erosive and unstable decomposed granite watershed that had been heavily logged in the past. The Grass Valley Creek watershed work borrowed from and ultimately mimicked the approach taken in Redwood National Park, however, the evolution from secondary surface treatments to road removals only took a year or so instead of a decade.

The primary goal of the Whiskey town project was to demonstrate "fish friendly" road treatments, ranging from out sloping and dipped out crossings to complete road removal Airphoto interpretatin revealed approximately 20 miles of abandoned logging roads, landings and skid trails Post treatment monitoring produced some interesting results According to McCullah, one of the sub-watersheds and its associated logging road had generated over 100 CY of sediment on an annual basis. After total removal of the road and recontouring of the slope the watershed has yet to produce 1CY after two years Approximately 10,000 CV of road fill was removed from the road crossings and placed back on the road bench from which it came The treatment costs, about $3-$5 per CY removed, are pretty representative for this level of road removal.

Secondary treatments included seeding and mulching with native grass. Heavy equipment was also used to mulch and cover the soil with limbs and trees removed from the old road bed. These actions completely eliminated surface erosion and have since reestablished the native grass component of the forest mosaic. McCullah and his students also experimented with biotechnical measures such as willow wattles, brush layering, fiber rolls, and live pole drains to stabilize the newly exposed stream banks and slopes.

McCullah believes that the most cost-effective approach to restoring naturally functioning watersheds in areas where ecosystem and fishery resources are critical is to identify and completely remove the roads that have a high potential to derange natura l hillside hydrology and to cause landslides.

Conclusions

Road decommissioning or removal is the key to successful and cost effective watershed rehabilitation following mineral extraction and timber harvesting operations. This remedy entails mechanical ripping and decompaction of old road beds, general restoration of original hillside contours by modifying the road prism, and excavation/removal of earthen fills in draw crossings. This primary treatment is normally accompanied by secondary measures or surface treatments aimed at stabilizing exposed soils and disturbed slopes. lasn


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