Why Use a Portable Timber Bridge?

Although most timber harvests disturb a small area for a short time, they have the potential to cause significant short-term impacts on soil and water quality. The primary impact of concern is erosion and sedimentation from roads, skid trails, stream crossings, and landings. Best management practices (BMPs) can be used in the design and construction of these areas to minimize erosion, and often they are required by law. If these areas are not properly stabilized after a harvest, they can continue to contribute sediment or cause other problems in the future. In aggregate these effects can deteriorate water quality throughout a watershed, causing problems locally and downstream.

Stream crossings in particular have been pinpointed as one of the top sources of sediment entering waterways during logging activity. Portable timber/skid bridges are often the best way to avoid sedimentation from temporary stream crossings during logging operations because they cause less soil disturbance than fords or culverts and do not inhibit streamflow or aquatic wildlife movement. They are also reusable, easy to install, and significantly cheaper than constructing a permanent bridge. They are relatively inexpensive to build, purchase, or rent (costs range from $1,500-20,000 depending on size and planned use; most skidder bridges average under $5,000). The planned use of a portable bridge can even reduce the permitting time needed for crossings that require a permit.

Providing cost share assistance for the construction or purchase of portable bridges is expected to increase the usage of this preferred stream crossing method over fords and culverts and decrease sedimentation of streams in the Upper Delaware basin.

1 Protecting the Source. The Trust for Public Land and American Water Works Association. 2004.
2 Cesa, Edward T., Bejune, Jeffery, and Melissa Strothers, eds. Portable Timber Bridges as a Best Management Practice in Forest Management. U.S. Department of Agriculture, Forest Service, Northeastern Area State & Private Forestry, National Wood in Transportation Information Center. March 2004.