How to Predict the Spread and Intensity of Forest and Range Fires- Richard C

United States Department of Agriculture How to Predict the Forest Service Intermountain Spread and Forest and Range Experiment Station Ogden, UT 84401 Intensity of Forest General Technical Report INT-143 June 1983 and Range Fires Richard C. Rothermel This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. THE AUTHOR RESEARCH SUMMARY RICHARD C. ROTHERMEL is a research engineer sta- This manual documents the procedures for estimating tioned at the Northern Forest Fire Laboratory in the rate of forward spread, intensity, flame length, and Missoula, Mont. Rothermel received his B.S. degree in size of fires burning in forests and rangelands. It con- aeronautical engineering at the University of Washington tains instructions for obtaining fuel and weather data, in 1953. He served in the U.S. Air Force as a special calculating fire behavior, and interpreting the results for weapons aircraft development officer from 1953 to 1955. application to actual fire problems. Potential uses Upon his discharge he was employed at Douglas Aircraft include fire predict ion, fire planning, dispatching, pre- Co. as a designer and trouble shooter in the armament scribed fires, and monitoring managed fires. group. From 1957 to 1961 Rothermel was employed by Included are sections that deal with fuel model selec- the General Electric Co. in the aircraft nuclear propulsion tion, fuel moisture, wind, slope, calculations with nomo- department at the National Reactor Testing Station in grams, TI-59 calculations, point source, line fire, inter- Idaho. In 1961 Rothermel joined the Northern Forest Fire pretations of outputs, and growth predictions. Laboratory, where he has been engaged in research on the mechanisms of fire spread. He received his master's degree in mechanical engineering at the University of Colorado, Fort Collins, in 1971. He was project leader of the Fire Fundamentals Research Work Unit from 1966 until 1979 and is currently project leader of the Fire Behavior Research Work Unit at the fire laboratory. The use of trade, firm or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the US. Department of Agriculture of any product or service to the exclusion of others which may be suitable. PREFACE outstanding analyst who straightened out our modeling and let the genie out of the bottle with publication of his When Hal Anderson and I came to the Northern Forest book of nomographs in 1976. That same year the first Fire Laboratory in 1961, it was not yet a year old and fire behavior officers' (FBO1s)course was organized at there was a feeling that surely this lab was going to con- Marana, Ariz. Ernie Anderson, director of the training tribute. Just what would be accomplished was not en- center at Marana, insisted thet we put together a fire tirely clear, but things were going to happen. There was prediction system that a man could use on the line or in also a sense of being overwhelmed, not only by all the a plans tent and teach it in 2 weeks. I am not sure how unknowns of wildfire behavior, but also by how to use to describe the early sessions, but students who have this brand new facility. There were at least two schools taken the course hail each other as graduates or sur- of thought in regard to the wind tunnels: (1) bring in box- vivors of the class of '76 or '77, etc. The course was suc- car loads of fuel from all over the country for burning in cessful; however, some of the early material was so the wind tunnels, and (2) weld the doors shut until a weak that the students should have chased all of us in- logical plan for use of the facilities was developed. structors off the base. Instead, their support encouraged We did not weld the doors and we did not ship in fuel us to improve the course and eventually to write this by the box-car load, but we did work hard at understand- manual. Students who successfully complete the course ing fire spread and adapting concepts of modeling and can now receive 2 hours of credit at the University of systems to the problems of forest fire prediction. During Arizona. the first 10 years a fire behavior model was produced. It Ernie Anderson also predicted that we would have took 10 more years to learn how to obtain the inputs and computers on the fireline. Three years later a project in- interpret the outputs for use by the "man on the itiated by John Deeming, Jack Cohen, and Bob Burgan, ground," which culminated in the writing of this manual. and finished by Bob Burgan, resulted in just that-a Specialized versions of the prediction methods have microchip for the TI-59 calculator. During the transition been available for some time in automated forms, such from nomograms to calculator, Pat Andrews from our as the National Fire Danger Rating System and the slash project has superseded me as an instructor at Marana; hazard appraisal system. her interest in applying research results has resulted in No manual of this size, covering the diverse material outstanding contributions to fire management. needed to analyze fire conditions, can be a solo produc- Instructors from many places have participated since tion. It could not have been done without the man who the first class. Steve Sackett took on the difficult task of crusaded for the laboratory facilities and who was the bringing realism to fuel moisture assessment and the first lab chief, Jack Barrows. His paper (Barrows 1951) tough job of providing fuel beds for burning each year. showed us "industry types" how fire could be examined, The meteorologists, Clyde O'Dell, Frank Gift, and Dave but more importantly his continual optimism and confi- Goens, have made that difficult subject understandable. -dence gave us the inspiration so necessary for a project The instruction for FBO's at Marana has now been that was to take 20 years to pull together. largely taken over by experienced field personnel who Many outstanding people have worked on this prob- were former students. Some have made outstanding con lem, as shown by the publications cited. I must single tributions to fire technology; these include Dave Aldrich, out a few for special acknowledgment, mostly members Rod Norum, Jim Elms, and John Chapman from the of Research Work Unit 2103 at one time or another. class of '76; George Rinehart, John Shepherd, Gordie No one could ask for a steadier and more reliable part- Schmidt, and Bill Williams, class of '77; Larry Keown, ner in a 20-year endeavor than Hal Anderson, who started Ed Mathews, Ron Prichard, Jan Van Wagtendonk, and M work at the lab with me in 1961. He and Jim Brown, who Templeton, class of '78; and Randy Doman and Steve came a couple of years later, are recognized leaders in Holscher from the class of '79. fuel research. Bill Frandsen joined the project in 1967 Of course the hardest workers on this text, with its and the scientific staff at that time consisted of just Bill endless tables, figures, exhi bits, exercises, and examples and me. Bill established the basis for the fire spread as well as revisions, have been Lucille Davis and Gladys model with his analysis of the conservation of energy on Look, our clerks, and Carolyn Chase, a mathematician a spreading fire. Charlie Philpot came to the lab while he who has organized all of the material for publication. was earning his Ph.D. under Dr. Shafizadeh at the Univer- This is not a complete list of contributors; others are sity of Montana and gave great assistance in the area of mentioned in the text, and considerable support came fuel chemistry. We were exceedingly fortunate to have from the directors at Marana, Ernie Anderson, Jerry excellent technicians during this time, including Merlin Mauk, and Dick Henry, and course leaders Joe Duft, Brown, who ran the wind tunnels, Bob Schuette, who Larry Mahaffey, Bonnie Turner, Hank LaSala, and Don constructed innumerable fuel beds, Walt Wallace, who Willis. The staff of the Intermountain Research Station handled the chemical analysis, and Bobbie Hartford, an must be recognized for its accomplishments in tech- invaluable assistant in the field and in the lab. nology transfer and for allowing so much time and effort In the late 60's the idea of fire management generated to be devoted to an area normally shunned by research. I a whole new list of problems for research that were appreciate their support. spelled out in a paper by Chandler and Roberts (1973). To everyone I express a heartfelt thank you. Fortunately, about this time we hired Frank Albini, an CONTENTS Page Page Introduction ................................. 1 Fuel Models with Dead Fuels Only ........... 46 Chapter I .Predicting Fire Behavior .............. 2 Fuel Models with Live and Dead Fuels ........ 46 Limitations ................................ 3 lnterpretation of Curves Displayed Applications ............................... 3 on the Nomograms ....................... 48 Predicting Fire Behavior ................... 3 Calculating Fire Behavior with the TI-59 Dispatching ............................. 3 Calculator ................................ 50 Planning ................................ 3 General ................................. 50 Prescribed Burning ........................ 4 Calculating Fire Behavior in Nonuniform Fuels Monitoring Fires .......................... 4 (The Two-Fuel-ModelConcept) ................ 53 The Fire Prediction Process ................... 4 Example of the Two-Fuel-Model Assess the Past and Present Concept Procedures ...................... 53 Fire Situations .......................... 4 Chapter IV .lnterpreting Fire Behavior and Determine Critical Areas ................... 4 Predicting Fire Growth ........................ 59 What Information is Needed and When ........ 4 Fire Characteristics Chart .................... 59 Estimate Inputs .......................... 4 Fire Growth from a Point Source ............... 63 Calculate Fire Behavior ...................

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