Road Alignment and Haul Routing in Estimating Sediment Delivery to Streams

The operational and environmental impacts of a conventional and a long-span yarding approach to forest management were simulated and compared in T12N R14E in the Ahtanum valley West of Yakima, WA. The conventional approach produced higher revenues at lower costs as expected, but delivered no more sediment to the stream than the long-span, no-new-roads approach. The explanation for this counter-intuitive result can be found in the density of the road network and its proximity to the stream. The road network produced a tenfold sediment increase over background levels, which might suggest a program of elimination and/or surfacing of existing roads. Analysis of this case, however, suggests that the construction of a ridge-based road network will be both environmentally and economically superior. This approach of integrating cumulative environmental impacts into the landscape scale harvest and transportation planning appears promising for identifying management options for reducing salmonid habitat degradation.