In order to complete an overall hazard assessment, each County Steering Committee reviewed historic data for the hazards categories presented in this plan: Dam Failure, Drought, Earthquakes, Emerging Infectious Disease, Flooding, Hazardous Materials, High Temperature, Landslide, Low Temperature, Pandemic, Severe Storms, Sinkhole/Karst, Terrorism, Tornadoes, and Winter Storms. Below is a summary of the rating system used by the local committees when assessing hazards.
Hazard Rating Criteria
Geographic Area/Population Affected is rated based on the percentage of the jurisdiction impacted by the hazard. For hazards that impact less than 10% of the jurisdiction, a rating of “negligible” is given. Hazards that impact 10-25% of the jurisdiction are rated as “limited.” Hazards that impact 25-75% of the jurisdiction are rated as “significant,” and hazards that impact 75-100% of the jurisdiction are rated as “Extensive.”
Maximum Probable Extent is calculated based off of classifications on a scientific scale noting the speed of hazard onset, duration of event, and resulting damage.
Probability of a Future Event is ranked based upon the likelihood of the event to occur in the next year or a recurrence interval of every 100 years. Hazards that have less than 1% probability of occurrence are scored as “unlikely.” Hazards that have a 1-10% of occurrence are scored as “occasional.” Hazards that have 10-90% probability of occurrence are ranked as “likely;” and hazards that have a 90-100% probability of occurrence in the next year are scored as “highly likely.”
The Overall Significance of a hazard is based on how the hazard ranks in the previous criteria. Hazards can be ranked as a low, medium, or high significance hazard based on the following definitions, provided by FEMA: Low: Two or more criteria fall in lower classifications or the event has a minimal impact on the jurisdiction. Medium: The criteria fall mostly in the middle ranges of classifications and the event’s impacts on the jurisdiction are noticeable, but not devastating. This rating is sometimes used for hazards with a high extent rating but very low probability rating. High: The criteria consistently fall in the high classifications and the event is likely/highly likely to occur with severe strength over a significant portion of the jurisdiction.