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RZRisk provides two adjective hazard ratings to capture two distinct conditions which influence potential wildfire loss.

The Site Hazard is related to the fuel loading in the immediate area, its propensity to burn and how easily such conditions might be mitigated.  This calculation generalizes the historical behavior of similar situations across the entire model area.  This value indicates how volatile the requested location could be should an ignition source be present.

The Zone Hazard relates to a the wildfire potential within a general area of similar fuel and terrain characteristics.  A location within or near a high-hazard zone may be susceptible to wildfire loss without regard to conditions on the specific site.  Conversely, a location with a high-hazard site may be at less risk due to reduced potential for major wildfires in the vicinity.  Consideration must be given to both Site and Zone hazards in order to effectively evaluate risk.

Zone Hazard
  • Very High – Wildfire could quickly produce significant flame lengths and ember showers.  Suppression may be difficult or impossible.
  • High – Wildfire and ember showers are possible and would require immediate suppression.
  • Moderate – A damaging wildfire is possible under adverse weather conditions.
  • Non-Wildland/Non-Urban – Wildfire is unlikely due to agricultural activity or barren land
  • Urban Unzoned – Urban density precludes the existence of wildfire in native fuels
  • No Data – Outside the model area
Site Hazard
  • Extreme – Any ignition source is dangerous.  Aggressive mitigation is strongly advised.
  • Very High – Flames or flying embers will cause ignition.  Mitigation is advised.
  • High – Ignition from approaching wildfire is likely.  All related precautions should be taken.
  • Moderate – Reasonable precautions will likely prevent ignition.
  • No Threat – The potential for ignition is negligible.
  • No Data – Outside the model area
Historical Fires
Historical wildfire data has been obtained from a variety of sources including CALFire, the National Inter-Agency Fire Center and the USGS Monitoring Trends in Burn Severity program (MTBS).  These datasets have been normalized and combined with careful attention to removing duplicates and ensuring that all perimeters reflect the final and maximum areas burned.

The presence of wildfires in the past can help interpret current hazard.  Regular large fires in the vicinity are a clear indication that fuel hazards exist and that weather conditions often favor conflagration.  Regular small fires may indicate either reduced hazard over time due to urban development and/or prompt suppression — but ignitions are a problem.  A pattern of large and small fire occurrence may reveal a cyclical probability due to vegetation type.

Dynamic overlays of Site and Zone Hazard ratings can be toggled on and off from the layer control.  Historical wildfire layers can also be shown on the map.  These are organized by decade and appear as progressively fainter perimeters based on age.  Perimeters are also labeled by name and year when zoomed to more detailed levels.  Several background maps are also available to facilitate navigation and a better understanding of adjacent development, vegetation, terrain and elevation.

More information about RZRisk can be found at RZRisk Product Overview.  For technical support, please call 303.386.3955 or email techsupport@redzone.co
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