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Fine fuel hazard levels are converted to an equivalent fine fuel load (t/ha). While coarser fuels are consumed during a fire, the combustion of fine fuels is the process that predominantly determines spread rates. Fuels are considered as three separate strata; surface (which includes near-surface fuels), elevated fuel and bark, in accordance with forest fuel measurement standards in Southern Australia (McCarthy et al. 1999; Hines et al. 2010). Fuel classes that have no elevated or bark fuels are considered by PHOENIX as grasslands and are processed using functions derived from the CSIRO grassland fire spread model (Cheney et al. 1998).
Table 3. PHOENIX fuel types currently recognised in southern Australia.
Veg Type | Code | FuelCode | Description | Fuel Characteristics |
|---|---|---|---|---|
Forest | F01 | 15 | Rainforest | dense vegetation with little dead material, epiphytes, vines, ferns, rarely dry |
| F02 | 32 | Wet Forest with rainforest understory | wet sclerophyll forest with a mesic understorey |
| F03 | 13 | Riparian Forest shrub | dense vegetation but with a small proportion of dead material |
| F04 | 11 | Wet Forest shrub & wiregrass | high biomass forest, but with little dead suspended material unless wiregrass present |
| F05 | 12 | Damp Forest shrub | dense understorey and potentially high bark hazard (karri) |
| F06 | 40 | Semi-mesic Sclerophyll forest | forest with semi-mesic shrubs and flammable grasses, sedge understorey |
| F07 | 33 | Swamp Forest | dense Melaleuca forest with little understorey |
| F08 | 6 | Forest with shrub | potentially high bark hazard, shrubs moderate flammability (mixed jarrah/karri) |
| F09 | 7 | Forest herb-rich | potentially high bark hazard, little elevated fuel |
| F10 | 45 | Dry Forest shrubs | dry forest with continuous understorey, (southern jarrah) |
| F11 | 8 | Dry Open Forest shrub/herbs | dry forest with open understorey (northern jarrah) |
Grass/sedges | G01 | 16 | High Elevation Grassland | dense sward of tussock grasses or herbs, high cover |
| G02 | 4 | Moist Sedgeland / Grassland | dense sward, potentially high dead component, button grass |
| G03 | 29 | Ephemeral grass/sedge/herbs | dense grass and sedges with potentially high levels of dead suspended material |
| G04 | 20 | Temperate Grassland / Sedgeland | grasses and sedges widespread, but varying in biomass |
| G05 | 44 | Hummock grassland | hummock grassland, discontinuous surface fuels |
Herbs | H01 | 30 | Moorland / Feldmarks | low flammability cushion plants |
| H02 | 36 | Alpine herbland | dense, upright, low flammability herbs |
| H03 | 34 | Wet herbland | freshwater herbs on mud flats |
| H03 | 37 | Wet herbland | low herbs in seasonally inundated lakebeds or wetlands |
Mallee | M01 | 27 | Mallee chenopod | low flammability except after exceptional rain bringing grasses |
| M02 | 42 | Mallee grass | mallee woodland with predominantly grass understorey |
| M03 | 25 | Mallee shrub/heath | continuous shrub layer but amount of dead material depending on species present |
| M04 | 26 | Mallee spinifex | discontinuous fuels, very flammable under windy conditions |
Bare | NIL | 0 | Water, sand, no vegetation | fuel absent |
Plantations | P01 | 98 | Softwood Plantation | dense canopy with continuous surface fuels |
| P02 | 99 | Hardwood Plantation | uniform canopy with continuous surface fuels |
Shrubs | S01 | 17 | High Elevation Shrubland/Heath | dense cover of shrubs with surface fuel largely under plants |
| S02 | 14 | Riparian shrubland | dense vegetation with little dead material |
| S03 | 35 | Wet Scrub | flammable shrubland with high level of dead elevated fuels |
| S04 | 1 | Moist Shrubland | dense shrubland, salt affected |
| S05 | 31 | Dry Closed Shrubland | tea-tree or paperbark thickets, little understorey |
| S06 | 21 | Broombush / Shrubland / Tea-tree | dense shrubland, but with relatively low level of dead material |
| S07 | 10 | Sparse shrubland | sparse shrubby vegetation with discontinuous surface fuels |
| S08 | 3 | Low flammable Shrubs | low flammability except after exceptional rain bringing grasses |
| S09 | 38 | Mangroves / Aquatic Herbs | trees, shrubs and herbs in permanent water, unburnable |
Heaths | S10 | 23 | Wet Heath | dense heath possibly with dense sedgy undergrowth |
| S11 | 24 | Dry Heath | dense heath with significant amounts of dead material |
Woodland | W01 | 18 | High Elevation Woodland shrub | wooded area with shrubby understorey |
| W02 | 19 | High Elevation Woodland grass | wooded area with continuous grass tussocks |
| W03 | 97 | Orchard / Vineyard | orchard or vineyard |
| W04 | 2 | Moist Woodland | low trees, shrubby, sedgy understorey, bark hazard |
| W05 | 22 | Woodland bracken/shrubby | wooded area with varying understorey, but not heathy |
| W06 | 9 | Woodland Grass/Herb-rich | surface fuels dominated by grass and herbs |
| W07 | 5 | Woodland Heath | flammable shrubs and high bark hazard |
| W08 | 41 | Gum Woodland heath/shrub | gum woodland with moderate bark hazard, heath/shrub understorey |
| W09 | 43 | Gum Woodland grass/herbs | gum woodland with moderate bark hazard, herbaceous understorey |
| W10 | 39 | Savanna grasslands | tall flammable grasses in an open woodland |
| W11 | 28 | Woodland Callitris/Belah | low flammability except after exceptional rain bringing grasses |
4.2 Wind reduction factors
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4.3.1 PurposeFuel types are used in conjunction with the fire history layer to generate fuel levels at the time of the simulation. Based on the time of ignition specified by the user, fuel levels are calculated through the combination of fuel type and the time since the last fire using fuel accumulation curves defined in the fuel type conversion file. 4.3.2 BasisThis layer is based upon fire history provided by the user. 4.3.3 Assumptions and limitationsIn the case of overlapping fire histories, PHOENIX only uses the most recent fire occurrence. 4.3.4 User interactionsPHOENIX uses the fuel accumulation model (see Section 5.7: Fuel Accumulation) to calculate fine fuel hazard classes which are then converted to an equivalent fuel load (t/ha) for surface, elevated and bark fuels. The accumulation curves are part of the fuel type conversion file. The user can upload a supplementary fire history layer to PHOENIX to capture recent fire events or to explore the effect of hypothetical fires in the landscape. |
4.3.5 Description
Fuel types are used in conjunction with a user-provided fire history layer to create fuel layer information used in PHOENIX simulations and stored in the Fire Grid. The time since the most recent fire is used to estimate fuel levels using negative exponential accumulation curves (discussed in Section 5.7: Fuel Accumulation). As data is retained for only the most recent fires (see Figure 9), where historic fires are being simulated, the fire history layer must be adjusted to be representative of the appropriate conditions.
Figure 9. Diagram of how PHOENIX treats overlapping fire history. On the left, two fires have been mapped, one in 1972 and the other in 1985. On the right, a new fire in 2008 has overlapped these earlier fires and has replaced their fire history in the overlapping areas.
ESRI Shapefiles can be used to supplement the baseline fire history layer for particular simulation runs. This provision is made to account for fires that have occurred since the baseline fire history was processed or to enable hypothetical prescribed burning scenarios to be quickly evaluated. The supplementary fire history is added to any existing fire history layer and processed in the same manner as the fire history stored in the Fire Grid.
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The width of the disruption will be used in PHOENIX to determine the effect of the disruptions on the local fire intensity and will determine if the local fire intensity is sufficient to breach the disruption. This is discussed in Section 5.5: Road / River / Break Impact.
4.8 Weather
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4.8.1 PurposePHOENIX requires weather data to support its fire spread models. 4.8.2 BasisPHOENIX can incorporate spatially gridded weather data, in NetCDF format, as produced by the Bureau of Meteorology. Alternatively, the user can provide a stream of weather data for a particular point in the landscape and at known intervals of time. 4.8.3 Assumptions and limitationsWhere weather data is provided as a stream of point data, the same weather conditions are assumed to apply for the entire fire. PHOENIX does not discriminate between forecast and observed data. 4.8.4 User interactionsThe user can download gridded weather from the Bureau of Meteorology. A downloading tool has been developed to assist and automate this process. Alternatively, the user inputs a stream of weather data at specified time intervals. Grass curing can input into PHOENIX simulations as part of a point weather stream, gridded weather input or as a separate spatial data layer. In the case of the passage of a cold front, additional entries may be added to the dataset immediately before and after the front's impact if a sudden change is wanted. Excluding this will result in a gradual shift in conditions from weather conditions input at the time step before the change and the time step after the change. |
4.8.5 Description
To initialise PHOENIX to process fires on a particular day, the appropriate daily values for Drought Factor (Finkele et al. 2006) and grass curing (McArthur 1966) are required. The Drought Factor, an index of fine fuel availability developed specifically for the McArthur forest fire spread model, is derived from the number of days since rain and the Keetch-Byram drought index (Keetch and Byram 1968). When using PHOENIX to make future predictions, forecast rain may need to be considered to estimate Drought Factor.
PHOENIX provides a tool to download NetCDF data provided by BoM. NetCDF data is an open data standard used internationally to create and share data. Currently, only spatially gridded weather data compatible with the Australian Bureau of Meteorology's Gridded Forecast Editor (GFE) tool are supported.
The NetCDF files produced by the Bureau of Meteorology and used by PHOENIX are:
- Surface Temperature (oC);
- Surface (10m) Wind Speed (km/h);
- Cloud Cover %;
- Surface Relative Humidity (%);
- Surface (10m) Wind Direction (deg.);
- Drought Factor (0-10);
- Grass Curing (0-100%); and
- KBDI – Keetch-Byram Drought Index (0-200).
In Victoria and Tasmania, the resolution of the gridded weather forecast data is currently about 3 km, but in Queensland, NSW, WA, and South Australia, the NetCDF weather data has about a 6 km spatial resolution. All NetCDF data used currently has a one-hour temporal resolution.
Figure 10. Victorian gridded Temperature data for 11 am 7 February 2009.
Alternatively, a string of weather data can be specified. Values for the air temperature (oC), relative humidity (%), wind direction (deg), wind speed (km/h), drought factor (0-10), degree of grass curing (%) and cloud cover (%) for specified times must be provided as specified in Table 4. An example is provided in Table 5.
Table 4. Standard weather attributes
Attribute | Comments |
|---|---|
Date/Time | Date and time of weather condition |
Temperature | 10 minute average in °C measured at 1.5 metres in a screen |
Relative Humidity | 10 minute average as a %, measured at 1.5 metres in a screen |
Wind Direction | 10 minute average in degrees, measured at 10 metres in the open |
Wind Speed | 10 minute average in km/h, measured at 10 metres in the open |
Drought Factor | Fine fuel availability 0-10 |
Curing | Grass curing level as a % (0-100) |
Cloud | Cloud cover as a % (0-100) |
Table 5. An example of user-provided point stream weather inputs that are time-stamped
