The Rothermel Fire Spread Model: A 50-year milestone in fire research

Submitted by firelab on Fri, 03/03/2023 - 09:17

In 1972, Richard C. Rothermel published his pioneering modeling work. Fifty years later in 2022, it was commemorated as the most widely used tool for wildfire behavior modeling, not only in the US but throughout the world. The development of his model and the associated research was conducted in the 1960s and 1970s at the Missoula Fire Sciences Laboratory. The “Rothermel Model” is embedded in dozens of computerized fire behavior systems used for fire management planning, training, and operational predictions. Rothermel was honored in November 2022 with an award for “outstanding contribution to fire science” at the International Conference for Forest Fire Research in Coimbra, Portugal.

Rothermel’s paper “A Mathematical Model for Predicting Fire Spread in Wildland Fuels” detailed the structure and function of a quasi-empirical model for calculating the steady state spread rate and intensity of a wildland surface fire. The achievement was based on a decade of experimental and theoretical work by Rothermel and his numerous colleagues in the Fire Physics Project at the Missoula Fire Science Laboratory, then called the Northern Forest Fire Laboratory. The model was implemented immediately in 1972 for the new National Fire Danger Rating System (NFDRS) for determining indices of potential fire activity and behavior – and it remains used in this capacity today. However, a wider range of uses for this revolutionary model were also envisioned in those early days, including localized fire behavior prediction, large-scale simulation of wildfires, and planning for fuel treatments and prescribed burning. Applications for all of these needs, and many more, have come into operational use in the succeeding decades.

The broad and continuing success of the Rothermel Model is partly due to the practical input requirements and the reasonable predictions that are robust to uncertainties. With wildfire predictions restricted to the steady state spread of a linear heading fire, the complexity of fuel and environmental conditions could be greatly simplified. Fuels are described with stylized fuel descriptions called “Fuel Models” that span a wide range of highly complex vegetation conditions. Wind and topographic slope effects in any combination are readily obtained for spatial fire modeling. This model and its input requirements have established many standards used throughout the wildland fire world, the origins of which are now largely taken for granted. It is interesting to contemplate how fire behavior science and fire management would look today without this foundational work.

Looking forward to the next half-century, escalating challenges in managing wildfires and their impacts will be faced. To meet these needs, a large and growing worldwide research community continues to pursue both improved knowledge of fire physics and practical advances in fire modeling. Despite enjoying immense advantages in technology, the enduring difficulties of wildfire science and associated development of practical tools routinely reminds us of the significance of achievements by Rothermel and his team in producing the spread model over 50 years ago.

Video interview with Mark Finney

In the fall of 2022, Mark Finney sat down with Dick Rothermel to discuss the early years of the Missoula Fire Lab, and the research that lead to the landmark publication of the paper "A Mathematical Model for Predicting Fire Spread in WIldland Fuels" 50 years after its initial publication. View the interview "Reflections on the publication of A Mathematical Model for Predicting Fire Spread in Wildland Fuels 50 Years Later" below or on the USDA Forest Service channel.