Proposed Method to Assess Timber Harvesting Roads

Timber harvesting roads, skid roads, and truck roads have been identified as major sources of stream sedimentation during logging operations. Researchers have stated that the planning for timber harvesting road networks is key to reducing these erosion and stream sedimentation sources. One impediment to reducing stream sedimentation is that planners do not have a way to quantify road network sufficiency and efficiency, particularly for those networks used by rubber-tired skidders during cable skidding operations. Reach capacity and excess reach capacity are proposed as ways to measure road network sufficiency and efficiency. Reach capacity is defined as the percent of a tract covered by a zone of specified distance around each road segment. Reach capacity is a measure of that portion of the tract that can be reached with a winch cable from the road system to move trees to the road for skidding. Excess reach capacity is the total area of all possible road zone overlaps expressed as a percentage of the reach capacity. Excess reach capacity is a measure of road duplication or the portion of the tract that can be serviced by more than one road. Use of these metrics will provide logging road planners with a tool to compare two or more proposed road network alternatives on a particular logging job, or to assess a completed road network. The Global Positioning System and the geographic information system were used to gather data and perform the spatial analysis necessary to acquire the metrics. A case study illustrates the proposed assessment method.