City of Irvine
2020 Local Hazard Mitigation Plan
Table 3-2 shows the Criterion Scoring used to assign a score for each criterion.
Table 3-2: Criterion Scoring
Probability
Maximum Probable Extent (Primary Impact)
The estimated likelihood of occurrence based on historical data.
The anticipated damage to a typical structure in the community.
Probability
Score
Impact
Score
Unlikely — less than a 1 percent chance each year. Occasional — a 1 to 10 percent chance each year.
1 2
Weak — little to no damage
1 2
Moderate — some damage, loss of service for days Severe — devastating damage, loss of service for months
Likely — a 10 to 90 percent chance each year.
3
3
Highly likely — more than a 90 percent chance each year.
4
Extreme — catastrophic damage, uninhabitable conditions
4
Location
Secondary Impact
The projected area of the community affected by the hazard.
The estimated secondary impacts to the community at large.
Affected Area
Score
Impact
Score
Negligible — affects less than 10 percent of the planning area.
1
Negligible — no loss of function, downtime, and/or evacuations Limited — minimal loss of functions, downtime, and/or evacuations Moderate — some loss of functions, downtime, and/or evacuations High — major loss of functions, downtime, and/or evacuations
1
Limited — affects 10 to 25 percent of the planning area. 2
2
Significant — affects 25 to 75 percent of the planning area. Extensive — affects more than 75 percent of the planning area.
3
3
4
4
After calculating the total impact score for each hazard (sum of the location, maximum probable extent, and the secondary impact). FEMA guidance recommends multiplying the total impact score by the overall probability to determine the final score for each hazard. A final score between 0 and 12 is considered a low-threat hazard, 12.1 to 42 is a medium-threat hazard, and a score above 42 is considered a high-threat hazard. This final score determines the prioritization of the hazards. Table 3-3 shows the individual criterion scores, the final score, and the threat level for each hazard based on the above prioritization process.
Earthquakes are high priority hazards because they are likely to happen, affect a wide area, and can be very damaging. Source Image: from Jonathan Nourok.
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