- Author
- Rothermel, R. C.
- Title
- Predicting Behavior and Size of Crown Fires in the Northern Rocky Mountains.
- Coporate
- Intermountain Fire Sciences Lab., Missoula, MT
- Report
- Research Paper INT-438, January 1991, 46 p.
- Keywords
- forest fires | wildland fires | fire behavior | fire spread | wind effects | plumes | flame length | energy transfer
- Identifiers
- crown fires; fireline intensity; available fuel
- Abstract
- Assessment of crown fire conditions calls for two important udgments: (1) identifying conditions for the onset of severe fires, and (2) predicting the spread rate, intensity, and size of expected crown fires. This paper addresses the second problem and provides methods for making a first approximation of the behavior of a running crown fire in fuels and weather conditions of the Northern Rocky Mountains in the Western United States. Rate of spread is developed from field data correlated to predictions of Rothermel's surface fire spread model. Energy release from surface fuels is obtained from Albini's burnout model. Fireline intensity is estimated from Byram's model. Flame lengths are estimated from Thomas' model. Energy rate, or power developed by the fire and ambient wind, is developed from Byram's equations and used to ascertain the possibility of a wind-driven or plume-dominated fire. The characteristics of these fires and dangers to fire fighters are discussed. A simple elliptical model is developed for estimating the area and perimeter of a large fire. The paper is oriented for use by well-trained fire behavior analysis to use in the field without the aid of computers to assess the characteristics of running crown fires.