CONTENTS 



Page 



INTRODUCTION 1 



METHODS 3 



Fieldwork 3 



Analysis 4 



RESULTS AND DISCUSSION . . . . 8 



Depth Versus Intercept Counts 8 



Bulk Depth Versus High Intercept Depth 11 



Effect of Lopping 13 



HAZARD Model Application 13 



Fuel Bed Depth Prediction 17 



Foliage Loss and Settling 18 



SUMMARY 21 



REFERENCES 21 



RESEARCH SUMMARY 



Development of equations for predicting fuel bed depth (called "bulk 

 depth" herein) appropriate for modeling fire behavior in slash is de- 

 scribed. Bulk depth (y) was correlated with the expected number of 1/4- 

 to 1-inch-diameter particle intercepts per foot of vertical plane transect 

 (x) by regressions of the form y = a\x~. Values of "a" suitable for use in 

 fire models were 0.767 for high-lead harvest debris, 0.940 for precom- 

 mercial thinning of pines, 1.22 for precommercial thinning in several 

 other western conifers, 0. 877 for ground-lead harvest debris in pines, 

 and 0.542 for ground-lead harvest in other species. Lopping of slash 

 reduced average depth 17 percent for harvest debris and 31 percent for 

 precommercial thinning debris. Correlation of high intercept depth 

 (maximum height of sampled fuel particles) with bulk depth showed that 

 the bulk depth can be well predicted using 64 percent of the more easily 

 measured high intercept depth. 



Models for settling of slash, retention of foliage and fine twigs, and 

 species mixing, useful in preparing data for fire models, are presented. 

 Application of the models in a slash hazard appraisal computer program 

 is illustrated. 



