Monday, January 1, 2001

January BMP Q&A

By: Hughes Simpson, BMP Forester, Texas Forest Service

Q:   Due to the fact there were no questions this month, I would like to look in detail at some of the problems noted in the latest round (Round 4) of BMP compliance monitoring.

A:   The report, “Voluntary Compliance with Forestry Best Management Practices in East Texas,” noted two areas requiring improvement in the evaluation of 150 forestry sites from June 3, 1998 to August 31, 1999. The first shortfall was sedimentation from stream crossings. The second area of concern was erosion problems from skid trails and temporary roads. This month let’s look at the problem with skid trails and temporary roads in closer detail.

The major problems associated with skid trails and temporary roads, identified by the report, were not being well drained or stabilized with appropriate structures. These areas can erode severely and contribute a large amount of sediment to streams if not properly constructed. This impact to water quality can be greatly reduced with proper planning. During the planning stage of your harvest operation, use tools like aerial photographs, topographical maps, and soil surveys in combination with an actual on the ground field evaluation to determine site conditions. These practices can help in determining the proper placement of roads and trails.

When laying out road systems, try to achieve the best possible grade, avoiding slopes greater than 15%. This is not always possible, so installing a slant or zig-zag pattern may be necessary to prevent a directed water flow. Natural drainage areas requiring Streamside Management Zones should not be used for road locations or other traffic areas. Rutting should be minimized on wet soils to reduce the impact to water quality.

Upon completion of the harvest operation, skid trails and temporary roads should immediately be protected from erosion. One way to accomplish this is by constructing waterbars to allow for proper drainage. These structures should be installed at a 30 to 45 degree angle downslope, with an outlet to allow water to drain off the road. Improperly built waterbars can function as water dams, which trap the water and create more problems. A chart located on page 53 in the Texas Forestry Best Management Practices “Bluebook” shows the suggested spacing between waterbars.

Another way to protect skid trails and temporary roads from erosion is by placing wing ditches along travel areas. These devices allow water to be diverted from the roadway into undisturbed areas. This process also reduces the speed and amount of flowing water, the major cause of erosion. Runoff water should be spread at the outlet, not dumped directly into drainages or stream channels.

Permanent vegetative cover can also be established to offer greater protection. Seeding is an option on skid trails and temporary roads if disturbed soil areas are not expected to revegetate naturally in time to prevent erosion. Logging slash and brush can also be positioned along the roadway to achieve the same effect in a more economical way. If you have a question regarding BMPs, please call me at (936) 639-8180.

* This article was published in the January 2001 issue of the Texas Logger

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