Graduate Thesis Or Dissertation
 

Stream protection and three timber falling techniques : a comparison of costs and benefits

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  • The objective of this study was to quantify the amounts of logging residues that are added to mountain stream channels as a result of timber falling - logging procedures, and to evaluate these procedures with respect to both ecologic and economic considerations. Three falling - logging treatments were observed: Conventional falling, Cable-assist falling, and Conventional falling with streamside buffer strips. Streamside environmental impact was evaluated in terms of the potential for damage due to the addition of organic logging residues to stream channels. Economic considerations included stream debris removal, timber volume left unharvested in buffer strips, timber falling labor and equipment, and timber breakage. H Stream debris was quantifie& for ten headwater streams in western Oregon prior to logging, after falling, and after yarding. To determine timber falling breakage and direct falling costs for both conventional and cable-assist methods, over 1.6 million board feet of timber was observed during falling operations. Results show that buffer strips were most effective in preventing logging debris from reaching stream channels. A 160 foot wide buffer strip allowed no debris penetration. During falling operations, 1.8 and 2.0 tons of debris per 100 feet of stream penetrated buffers with widths of 36 and 15 feet respecttively. Conventional falling added an average of 47 tons of debris per 100 feet of stream. Cable-assist falling added only 14 tons per station, thus demonstrating its applicability as a stream protection technique. Stream debris removal costs were found to be quite low for the observed buffer strip units. Estimated clean-up costs for the conventional falling treatment averaged $400 per station compared to only $154 per station for cable-assist falling. Timber falling production rates averaged 9.3 MBF per hour for conventional falling, and 6.3 MBF per hour for cable-assist falling. Due to lower production rates, larger falling crews, and additional machinery costs, direct falling costs for cableassist falling averaged $8.02 per NBF (gross scale) compared to $3.33 per MBF for conventional failing. Timber breakage averaged 7.35 percent of gross scale for conventional falling compared to 5.92 percent for cable-assist falling, a difference. of 1.43 percent. For both methods, breakage increased as trees became larger and more defective. The total cost of the economic factors evaluated was applied to a hypothetical 40 acre setting of 2,800 MBF. The analysis showed that of all treatments, the narrow 15 foot wide buffer strip treatment was most economical, total cost being only $6.12 per MBF. Due to the high cost of leaving 285 NBF of timber the 160 foot wide buffer strip treatment was most expensive at $13.18 per MBF. For the conventional falling - logging treatment, the total cost per MEF was $7.93. This compares with $10.96 per MBF for cable-assist falling; savings of breakage and stream debris removal costs were offset by much higher direct falling costs. Although not included as a cost consideration in this analysis, cable-assist falling produced a greater average log length than did conventional falling. Consideration of log length relationships, and use of higher stumpage values would have altered the outcome of this analysis. The cable-assist treatment would have become more economically desirable compared to the conventional and buffer strip treatments.
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