H. Revegetation of Disturbed Areas
Reduce erosion and sedimentation by rapid revegetation of areas disturbed by harvesting operations or road construction:
- Revegetate disturbed areas (using seeding or planting) promptly after completion of the earth-disturbing activity. Local growing conditions will dictate the timing for establishment of vegetative cover.
- Use mixes of species and treatments developed and tailored for successful vegetation establishment for the region or area.
- Concentrate revegetation efforts initially on priority areas such as disturbed areas in SMAs or the steepest areas of disturbance near drainages.
1. Applicability
This management measure pertains to lands where silvicultural or forestry operations are planned or conducted. It is intended to apply to all disturbed areas resulting from harvesting, road building, and site preparation conducted as part of normal silvicultural activities. Disturbed areas are those localized areas within harvest units or road systems where mineral soil is exposed or agitated (e.g., road cuts, fill slopes, landing surfaces, cable corridors, or skid trail ruts).Under the Coastal Zone Act Reauthorization Amendments of 1990, States are subject to a number of requirements as they develop coastal nonpoint source programs in conformity with this measure and will have some flexibility in doing so. The application of this management measure by States is described more fully in Coastal Nonpoint Pollution Control Program: Program Development and Approval Guidance, published jointly by the U.S. Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce.
2. Description
Revegetation of areas of disturbed soil can successfully prevent sediment and pollutants associated with the sediment (such as phosphorus and nitrogen) from entering nearby surface waters. The vegetation controls soil erosion by dissipating the erosive forces of raindrops, reducing the velocity of surface runoff, stabilizing soil particles with roots, and contributing organic matter to the soil, which increases soil infiltration rates. In areas such as the Pacific Northwest, the construction of forest roads without revegetation has led to significant increases in stream sedimentation. According to Carr and Ballard (1980), studies have found that stream sedimentation increased 250 times during the first rainfalls following construction of a 2.5-km logging road within a 100-hectare watershed and remained higher than an undisturbed companion watershed for the next 2 years.Vegetation can trap and prevent dry ravel from moving further downslope, and it produces organic matter that is incorporated into the soil, increasing infiltration rates (Berglund, 1978). Nutrient and soil losses to streams and lakes also can be reduced by revegetating burned, cut over, or otherwise disturbed areas (Crumrine, 1977). In some cases, double plantings are used: an early planting to establish erosion protection quickly and a later planting to provide more permanent protection (Hynson et al., 1982).
3. Management Measure Selection
a. Effectiveness Information
This measure is based in part on information and experience gained from studies and from the use of similar management practices by States. Significant reductions in soil erosion have been achieved by revegetating bare cut-and-fill slopes alongside forest roads. A study of forest roadside slopes at two sites on Vancouver Island, Canada, by Carr and Ballard (1980) found revegetation to be an effective management practice in preventing soil erosion. At the control sites where no plant cover was present, the soil eroded to an average depth of 2-3 cm over 7 months, amounting to an estimated soil loss of 345 cubic meters per kilometer of road. In contrast, sites with hydroseeding had a net accumulation of soil material. In terms of practices, a single hydroseeding application of both seed and fertilizer was as effective as sequential hydroseeding application of seed and fertilizer in terms of preventing soil erosion. The practice of mulching on non-gully-prone soils, as a supplement to hydroseeding, was found to be unnecessary because mulch is incorporated into the hydromulch.Kuehn and Cobourn (1989) studied the Basic Erosion Rate (BER) for soils on commercial forest land in the Eldorado National Forest and concluded that good ground cover is key to reducing erosion. Figure 3-26 demonstrates the relationship between percent ground cover and slope, and the resulting soil loss. Good ground cover is defined as "living plants within 5 feet of the ground and litter or duff with a depth of 2 inches or more."
Seeding was also cited by Berglund (1978) as a successful management practice for controlling erosion along forest roads in Oregon. When establishing a revegetation erosion control program, the author suggested that the program address criteria for seed selection, site preparation guidelines, timing of seeding, application methods, fertilization, and mulching. Several guidelines for seed cover, fertilization, and mulching rates were also presented. For example, Berglund suggests that a vegetative cover of 40 percent or more is necessary to significantly reduce soil erosion from disturbed areas.
Bethlahmy and Kidd (1966) described the extent to which revegetation controls erosion from steep road fills as dependent upon the amount of protection given to the seeded slopes (Table 3-54 (10k)). Seed and fertilizer alone did not control erosion, but the addition of straw mulch reduced erosion by one-eighth to one-half. Adding more protection, netting as well as mulch, reduced erosion by almost 100 percent to nearly negligible levels.
b. Cost Information
Megahan (1987) found the costs of seeding with plastic netting placed over the seeded area to be almost 50 times more than the costs of dry seeding alone (Table 3-55). The economic impacts of other revegetation management measures were estimated by Dubensky (1991)(Table 3-56). Seeding firelines or rough logging roads adds $19.75 per 100 feet of road or fireline. Ripping, shaping, and seeding log decks costs about 178.50 per log deck. Fiber for road and landing maintenance adds $4 per ton used, and water bars add $12.50 each for construction and seeding.
Lickwar (1989) compared the costs for revegetation of disturbed areas for various slope gradients in the Southeast. He found that revegetation costs decreased slightly as slope decreased; however, costs remained fairly high (Table 3-57). Minnesota's Stewardship Incentives Program (SIP) estimated the costs of reestablishment of permanent vegetation to vary from $80.00/acre to $147.00/acre of disturbed area, depending on type of vegetation (Table 3-58).
4. Practices
As described more fully at the beginning of this chapter and in Chapter 1, the following practices are described for illustrative purposes only. State programs need not require implementation of these practices. However, as a practical matter, EPA anticipates that the management measure set forth above generally will be implemented by applying one or more management practices appropriate to the source, location, and climate. The practices set forth below have been found by EPA to be representative of the types of practices that can be applied successfully to achieve the management measure described above.
The selection of appropriate grasses and legumes is important for vegetation establishment. Grasses vary as to climatic adaptability, soil chemistry, and plant growth characteristics (Berglund, 1978). USDA Soil Service technical guides at the State-wide level are excellent sources of information for seeding mixtures and planting prescriptions (Hynson et al., 1982). The U.S. Forest Service, State foresters, and County Extension agents can also provide helpful suggestions (Kochenderfer, 1970). The use of native species is important and practical. Because non-native species can take over and destroy native vegetation, use of non-native species often results in increased maintenance activities and expense, and plenty of hardy native species are usually available (Hynson et al., 1982). In addition to selecting a seeding mixture, the seeding rate must be determined so that adequate soil protection can be achieved without the excess cost of overseeding. Berglund (1978) describes how to determine seeding rates in Seeding to Control Erosion Along Forest Roads.
These species may be established more effectively than grass and are preferable for binding soils.
Timing will depend on the species to be planted and the schedule of operations, which determines when protection is needed (Hynson et al., 1982).
Critical, first-year mulch applications provide the necessary ground cover to curb erosion and aid plant establishment (Berglund, 1978). Many different kinds of mulches can be used to improve conditions for germination (Rothwell, 1978). Various materials, including straw, bark, and wood chips, can be used to temporarily stabilize fill slopes and other disturbed areas immediately after construction. In most cases, mulching is used in combination with seeding and planting to establish stable banks. Both the type and the amount of mulch applied vary considerably between regions and depend on the extent of the erosion potential and the available materials (Hynson et al., 1982). Figure 3-27 is a summary of mulching effectiveness in reducing erosion.
Fertilization is often necessary for successful grass establishment because road construction commonly results in the removal or burial of fertile topsoil (Berglund, 1978). To determine fertilizer formulations, it is best to compare available nitrogen, phosphorus, potassium, and sulphur in the soils to be treated with the requirements of the species to be sown (Rothwell, 1978). It may be necessary to refertilize periodically after vegetation establishment to maintain growth and erosion control capabilities (Larse, 1971; Berglund, 1978).
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If the stand is over 60 percent damaged, reestablish it following the original specifications.
Possible methods include mulching (without seeding) and installation of commercially produced matting and blankets. Alternative methods for planting and seeding include hand operations, the use of a wide variety of mechanical seeders, and hydroseeding (Hynson et al., 1982).
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