PHYSICAL MODELING OF LEAF SCORCH HEIGHT FROM PRESCRIBED FIRES IN YOUNG EUCALYPTUS-SIEBERI REGROWTH FORESTS IN SOUTH-EASTERN AUSTRALIA

Information on weather, fuel and fire behaviour were recorded on 56 ex perimental prescribed fires in young coastal silvertop ash (Eucalyptus sieberi) regrowth forest in south-east New South Wales, Australia. Th e thermal environment above the fire was measured in 14 of those fires . Existing plume models, based on the assumption of a uniformly burnin g line fire, were found to under-predict the temperature of the air ri sing into the canopy. An axially symmetric plume model, based on the o bservation that fires burning in non-uniform fuels are not uniformly b urning line fires, was developed using standard plume rise equations. This model, called the Sporadic Axial Model (SAM), was calibrated usin g data from one fire. This model can be used to predict scorch height from known ambient temperature and Byram's fire line intensity. The SA M model suggests that scorch height will be greater for prescribed fir es burnt under calm conditions than prescribed fires of the same inten sity burnt under stronger wind conditions.