City of Irvine
2020 Local Hazard Mitigation Plan
economic activity that would normally occur during the period of the outage. Structures, like telephone poles or power transmission towers which are felled by the shaking, could potentially block roadways and prevent emergency response teams from reaching victims or evacuees who need assistance.
Severe Weather
Physical Threat
Severe weather could affect all parts of Irvine, so all CFs and FOC are within this hazard zone. The three most common severe weather events that could affect Irvine include extreme heat, severe wind, and rain. Extreme Heat Very high temperatures can cause roads to deform and buckle as the concrete expands in the heat, especially in weaker spots in the pavement, such as areas that have not been maintained well. Power lines and other sections of the electrical grid are less effective in higher temperatures and may suffer damage due to stress during extreme heat events. Buildings with dark pavement will absorb more heat than the surfaces with vegetation or lighter materials, which are better at reflecting the sun’s energy. This urban heat island effect is strongest during hot periods when the sun is strongest. Severe Wind Intense winds likely present the greatest threat to physical structures, particularly from trees or branches that fall on buildings and cause substantial damage. Older structures that have deferred maintenance or have not been retrofitted for high wind conditions may suffer greater damage in comparison to newer/updated structures. Utility lines and wooden utility poles face an elevated threat from wind, as do buildings without reinforced roofs. Another physical threat associated with severe wind is wildfire impacts and the recent practice of electric utilities conducting Public Safety Power Shutoff activities. During high wind events, these shutoffs may impact structures that rely on electricity for normal operations. See social threats for population impacts that may also occur as a result of these events. Rain Rain could damage any structures with poorly constructed roofs and could also erode the soil around building foundations. Heavy rain could also lead to flash flooding, which would damage unelevated structures in flood zones. Heavy rains are most likely to cause damage to structures located on slopes and along stream courses, where the risk of erosion is the highest. Landslides triggered by heavy rains would damage any structures located below the landslide’s starting point.
Social Threat
Extreme Heat Whereas a heat event can be relatively harmless for those with a reliable means for staying hydrated and cool, it can be deadly for others. Young children, the elderly, or people suffering from serious medical conditions are physiologically more vulnerable to heatstroke. Some senior citizens also take medicines that can make it harder for their bodies to maintain a safe internal temperature, creating an additional
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