- Title:
-
Fuel Hazard Levels in Relation to Site Characteristics and Fire History: Chiltern regional park case study
- Date:
- October 1996
- Organisations
- DSE
- Authors:
- Karen Chatto
- Location:
- Victoria, VIC, Australia
Overview
Fire behaviour varies with changes in topography, weather and fuel. Of these three aspects, humans can only modify fuel. Fuel reduction burning aims to reduce the fire hazard by modifying fuel structure and quantity.
In recent years, the local Municipal Fire Prevention Committee, Friends of Chiltern Regional Park and the public have expressed concern about the high fuel quantities throughout Chiltern Regional Park.
Field sampling took place in mid-January 1995, assessing fine fuel depth, surface fine fuel quantity, bark hazard and elevated fuel hazard. Forest fuels were destructively sampled and the fine fuel component of the fuel was analysed. This component significantly affects fire behaviour. Bark hazard and elevated fuel hazard were assessed at each site as they also affect fire behaviour. Fuels were sampled across three overstorey vegetation classes, ten fire history classes and three site productivity classes. This study examined fine fuel accumulation rates across Chiltern Regional Park, determined fine fuel, bark and elevated fuel hazard levels, and mapped the Overall Fuel Hazard levels. This report summarises the findings of this assessment and recommends future management strategies.
A linear relationship was found between surface fine fuel load and litter depth, with depth explaining 89 percent of variation in fine fuel quantities of sites with low to moderate elevated fuel hazard. A negative exponential model was used to determine the relationship between each fuel component and time since fire. Within 3 years of fire, surface fine fuel loads had reached 95 percent of their predicted steady state levels, with only a moderate surface fine fuel hazard being predicted as the steady state level for all productivity sites and forest types. Within 9 years of fire, elevated fuel loads had reached 95 percent of their predicted steady state levels.
Despite taking three times as long as the surface fine fuel to re-accumulate, the elevated fuel has the potential to become a greater fuel hazard than the surface fine fuel. Bark hazard showed no relationship with time since fire, indicating that past prescribed fires have not had an effect on bark hazard. Bark hazard was related to forest types, being greatly influenced by the presence of stringybark. Areas of Very High bark hazard were of the Ironbark/ Stringybark forest type, whilst those areas of Moderate hazard levels were of the Gum/Box forest type.
Across the three forest types studied, all three have reached their potential Overall Fuel Hazard at the time of this study. Of the three classes, only the Ironbark/Stringybark forest type exceeds the recommended level of high for areas classified as Fuel Management Zone 2. Future fuel reduction operations should be aimed at reducing bark hazard and elevated fuel hazard in these areas, whilst taking into consideration any ecological requirements.
