HYDRO20750 - Laserfiche WebLink

Home Browse Search

contour-felling. This BAER treatment is expensive, technically demanding, and dangerous work, so crew skill and experience and good supervision are impor- tant. Attention to felling and delimbing safety rules is paramount. Logs must be placed on the contour, put in contact with the ground, and properly anchored. If these three items are ignored, failure is assured. This treatment needs to be implemented in a very methodi- cal and meticulous manner. Increased installation speed or area covered will not make up in effectiveness that can be lost by poor installation. Ground contact can be assured by adequate delimbing beneath each log, leaving branches downhill, trenching, and back- filling. In some instances machinery has been used to make ground contact trenches, but the usual method is to excavate with hand labor due to equipment and slope limitations. Trenchingto seat contour-felled logs has an additional benefit in that it can help to break up hydrophobic layers in the soil. Anchoring can be done with wooden or re-bar stakes where slopes are steeper, but should be of sufficient frequency and depth to prevent movement of the logs. Shallow, rocky soils that are very uneven are prob- lematicforanchoring, eo care moat be taken to ensure that logs are adequately secured to the slope. Overly rocky and steep elopes should be avoided, because benefits gained from contour-felling treatment can be easily offset by extra implementation time required and limited stabilization of small amounts of soil. Gentler elopes and finer textured soils (except clayey soils) lead to better installation and greater sediment trapping efficiency. Slopes less than 40 percent are recommended for successful contour-felling. Slopes greater than 7b percent present significant installa- tion safety hazards and should be avoided. In some instances, only the lowerportiona of slopes near ephem- eral orperennial channelehave been treated. In highly erosive soils derived from parent material such ae granitica or glacial till, so much sediment can be mobilized that it might overwhelm small centour- felled loge. Availability of adequate numbers of straight trees also affects this treatment. Specifications require loge from burned trees lb to 20 ft (4.5 to 6 m) in length with diameters of 4 to 12 in (100 to 305 mm). Placing tree stems 10 ft (3 m) apart on slopes over 50 percent, l6 ft (4.5 m) apart for elopes of 30 to 50 percent, and 20 ft (6 m) apart for elopes less than 30 percent would require 2000 to 40001inear ft ac 1(1500 to 3000linear m ha 1) of tree bole on some sites. A shortage of dead timber or large numbers of small diameter trees could place limitations on the contour-felled treatment area. Crooked stems, such ae oak, are often readily avail- able, but they are not useable or coat-effective for contour-felling treatment. Cutting trees for contour- felled log barriers reduces the number of snags for birds to use. However, it often increases vegetation cover when plants become established in fine sedi- ments trapped on the uphill aides of the felled loge. Contour-felled logs should be placed in s random pattern to ensure a more "natural" appearance and avoid patterns which might aggravate runoff. Mulch Purpose. Mulch ie used to cover soil, reducing rain impact and soil erosion. It is often used in conjunction with grass seeding to provide ground cover in critical areas. Mulch protects the soil and improves moisture retention underneath it, benefitting seeded grasses in hot areas but not always in cool ones. RelativeEti'ectiveness Excellent-66% Good-17% Fair- 17% Poor-0% (Replies = 12) Mulch was judged "excellent" in effectiveness by moat interviewees, although many also noted that it is quite expensive and labor-intensive (table 16). It is moat effective on gentle slopes and in areas where high winds are not likely to occur. Wind either blows the mulch offeite or piles it so deeply that seed germina- tion ie inhibited. On very steep slopes, rain can wash some of the mulch material downslope. Punching it into the soil, use of a tackifier, or felling small trees across the mulch may increase onaite retention. Mulch is frequently applied to improve germination of needed grasses. In the past, seed germination from grain or hay mulch was regarded as a bonus, adding cover to the site. Use of straw from pasture introduces exotic grass seed. Forests are now likely to seek"weed-free" mulch such as rice straw. Mulch is judged most valu- ableforhighvalue areas, such as above orbelowroad~, above streams, or below ridge tops. Implementation and Environmental Factors Mulch can be applied moat easily where road access is available because the mulch must be trucked in, although for critical remote areas it can be applied by helicopter or fixed wing aircrafta. Hand application is labor-intensive and can result in back or eye injuries to workers. Using a blower to apply the mulch re- quires considerable operator skill to get uniform distribution of the material. Effectiveness depends on even application and consistent thickness. Rice straw is not expected to contain seeds of weeds that could survive on a chaparral or forested site (too dry); however, weeds do germinate sometimes and could result in introducing new exotics to wildland areas. Other certified "weed-free" straws sometimes cen- tainnoxious weeds. There is concern that thick mulch inhibits native shrub or herb germination. Shrub seedlings have been observed to be more abundant at the edge of mulch piles, where the material was leas than 1 in (25 mm) deep. Because of the weed and 76 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-63.2000