SUMMARY 



To aid in modeling fire behavior for appraisal of slash hazard, equations were 

 developed for predicting fuel bed depth from the loading of 1/4- to 1-inch fuels. The 

 depth equations differed among precommercial thinning, ground-lead harvesting, and 

 high-lead harvesting systems and between pines and other conifers. Settling of slash 

 with age was weakly discerned; however, our findings, together with others, permitted 

 inference of a rough aging model that distinguishes between harvesting and precommercial 

 thinning . 



Depth of lopped slash was strongly related to depth of unlopped slash. A strong 

 relationship was also developed between the "bulk depth," useful in fire behavior 

 modeling, and the "high intercept" depth that is easily measured in the field. The 

 influence of merchantable tip diameter on slash depth was evident, although it was not 

 quantified. Accuracy of the depth relationships is probably adequate for most tree cut- 

 ting activities in western mountainous areas, except perhaps west side slopes along the 

 Pacific Coast. Here the large trees and methods of logging may result in depth/load 

 relationships different from ours. Depth predictions should be verified in the Pacific 

 Coast mountains before modeling fire behavior in slash. 



When predictions of fuel depth are coupled with predictions of slash loading (by 

 size class) from tree inventories, the depth models presented here allow prediction of 

 fire behavior before the slash is created. Hopefully, this information will aid in 

 timber sale planning and in management of slash fuels. 



REFERENCES 



Albini, Frank A. 



1976. Computer-based models of wildland fire behavior: a users' manual. USDA For. 

 Serv. Intermt. For. and Range Exp. Stn. , 68 p. Ogden, Utah. 

 Bevins, Collin. 



1976. An evaluation of the slash fuel model of the 1972 National Fire Danger Rating 

 System. M.S. thesis, Univ. Wash., Seattle. 104 p. 

 Brown, James K. 



1970a. Vertical distribution of fuel in spruce/fir logging slash. USDA For. Serv. 

 Res. Pap. INT-81, 9 p. Intermt. For. and Range Exp. Stn., Ogden, Utah. 

 Brown, James K. 



1970b. Ratios of surface area to volume for common fine fuels. For. Sci. 16:101-105. 

 Brown, James K. 



1972. Field test of a rate-of-f ire-spread model in slash fuels. USDA For. Serv. Res. 

 Pap. INT-116, 24 p. Intermt. For. and Range Exp. Stn., Ogden, Utah. 



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