Wildfire Risk Extreme scores involve contributions from 20 data layers. These layers vary widely in format, value range, and resolution. Some are raster layers, others come from geospatial vector formats, while still others are geo-referenced tabular datasets. To overcome these differences, various transformation scenarios are performed to arrive at a standard 0-to-75 value range for each output value. In all cases, a value of 0 means that a particular output has a minimal impact on wildfire risk, while a value of 75 means the opposite: The output contributes its full weight to overall wildfire risk. A value of -9999 is assigned to areas where data is lacking, or in cases where a factor is not applicable to a particular area (wildland versus intermix versus interface).
Related outputs are organized into six groups corresponding to the major factors that influence wildfire occurrence and consequences:
- Severity
- Frequency
- Community
- Mitigation
- Damage
- Urban Conflagration
A composite rating on a 0-to-75 scale is generated for each group. The combined influence of all groups generates the final RISK_LEVEL rating of overall fire risk. The relative weight of each input and the factor to which it contributes are what differentiate the three risk types – wildland, intermix, and interface.
By convention, all polygons designated as MLE (minimal likely exposure) or surface water have a RISK_LEVEL rating of 0.