INTRODUCTION 



Development of a mathematical model for predicting rate of fire spread is part of 

 an effort at the Northern Forest Fire Laboratory to formulate a system for appraising 

 the fire behavior potential of fuel. Desirable features of such a fuel appraisal system 

 are quantitativeness , predictability, and flexibility. 



A fuel appraisal system based upon quantitative inputs and outputs is needed for 

 objectively guiding fire management decisions. Appraisal of the fire spread potential 

 of fuel can help with evaluations of silvicultural treatments, prevention and presuppres- 

 sion planning, budgeting of fire control expenditures, fire simulation training, and 

 wildfire suppression. 



Earlier and existing systems of fuel appraisal, of which Hornby's (1935) is the 

 best known and most widely used, have been useful, but contain weaknesses that limit 

 their application for current and future resource management. The major weaknesses 

 seem to involve the following: 



1, A fixed level of fire-weather severity is required for making the evaluations. 

 "Average bad" conditions are assumed. Usually fuels are considered quite dry and winds 

 rather strong. 



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