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Characterising fires by asset impact can be useful for prioritising fires in a tactical scenario or strategically for quantifying the effectiveness of a specific treatment. Asset impact can be a more meaningful measure than traditional characteristics like fire area, average intensity, perimeter length, etc.
Against each cell of the input asset layer (e.g. 30 m grid) the user assigns an asset type, asset priority, an impact type and asset value in metres squared. This is described below.
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Only one asset ID can be stored per input data cell (e.g. 25 m or 30 m), but several asset IDs may be combined into a PHOENIX Fire Grid cell (e.g. 180 x 180 m).
Table 7. PHOENIX Asset ID (from Tolhurst et al. 2017)
Asset Id | Description | Priority | Impact Type |
|---|---|---|---|
1 | Housing | 1 | 2 |
2 | Infrastructure | 2 | 5 |
3 | Plantation | 3 | 5 |
4 | Catchment Tributaries | 4 | 4 |
5 | Catchment | 5 | 3 |
6 | Rainforest | 6 | 5 |
7.6.2 Impact type and loss functions
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For each asset type, an impact type must be assigned. Some indicative functions have been developed to indicate impacts on the following asset types: housing, infrastructure, plantations, catchments and rainforest (see Table 7). Currently, only five impact types have been defined (Table 8) and can only be edited through the modification of the base PHOENIX code. Users can define additional impact types and functions (up to 99 impact types). It is expected that these will be derived through empirical relationships. The impact type can be defined as a mathematical function (loss function), as with house loss. Alternatively, it can be defined as some fire characteristic threshold criteria such as an asset being exposed to a fire greater than a specified level of intensity (Table 8).
Table 8. PHOENIX asset impact type
Impact Type | Loss Description |
|---|---|
1 | Record loss if fire present |
2 | HouseLossProbability = see below |
3 | Intensity > 3,000 kW/m |
4 | Intensity > 10,000 kW/m |
5 | Intensity > 30, 000 kW/m |
The house loss probability function used in PHOENIX is described in Tolhurst and Chong 2011, and is shown below. Users can also choose to use their own house loss function. For example DELWP uses HouseLossProbability = Loss if Intensity > 10,000 kW/m or Ember Density > 2.5 embers/m2.
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Because each of the input data layers into PHOENIX are in ASCII format, only one value is possible from the input layer resolution cell (e.g. 30 x 30 m). To enable multiple pieces of information to be stored in a single integer value, a coding system is used (Figure 36). In Table 9, the integer value of 230312340 can be decoded as Asset ID 23, Impact Type 3, Asset Value of 1,234. The PHOENIX Integer Scientific Notation helps to interpret the 'asset value'. For example, when the scientific notation has a value of zero (0) as in this case, then the value is taken as is, i.e. 1,234, whereas for Asset ID 11 the Asset Value is 0.001234 because the scientific notation has a value of minus three (-3) which means x 10-3.
Figure 36. Asset code formulation.
Table 9. Worked examples of the PHOENIX asset code
Asset Id | Impact Type Code | Asset Value | PHOENIX Integer Scientific Notation | Asset Code |
23 | 03 | 1234 | 1234E+0 | 230312340 |
11 | 02 | 1.234567 | 1234E-3 | 110212343 |
3 | 17 | .0012345 | 0012E-4 | _31700124 |
1 | 43 | 50 | 0050E+0 | _14300500 |