Weaknesses of the NFFL models include poor representation of fuels that burn under high dead fuel moistures (such as occur in the Southeastern United States and Hawaii), and always modeling herbaceous fuels as fully cured. In recent years the NFFL models have also proven insufficient for new uses of Rothermel's spread model, such as modeling fire behavior in blowdown fuels, modeling the initiation of crown fire, simulating the effects of fuel treatments on fire behavior, and simulating changes in fuelbed characteristics over time.
In cooperation with the Missoula Fire Sciences Lab, we have developed a new set of fuel models. The new fuel models have been organized into 6 fuel-type classes: Grass, Grass-shrub, Shrub, Timber-other, Timber litter, Slash-blowdown, and Non-burnable. The new model set is designed to stand alone; none of the NFFL models is repeated exactly in the new set, but the range of behavior they predict encompasses the NFFL models. The fuel model key points to the new fuel models only. However, the NFFL models will still be available. If desired, both the new set and the NFFL models can use used at the same time, on the same map.
Fuel models with an herbaceous component are "dynamic". In a dynamic model, live herbaceous load is transferred to dead as a function of the live herbaceous moisture content. Fire behavior prediction systems must be modified to use the new dynamic models. FARSITE, FLAMMAP, BehavePlus and NEXUS have been or will soon be updated to accommodate dynamic fuel models.
The new set of fuel models is available now. Visit www.firelab.org to read more about the new fuel models and how to use them.