2020 Local Hazard Mitigation Plan

City of Irvine

or extreme storms. All expectations are that the probability they will occur again in the future is highly likely.

Climate Change Considerations

Extreme Heat The primary effect of climate change is warmer average temperatures. The hottest years on record have all occurred since the turn of the millennium, and 2016 and 2019 are currently the hottest and second hottest years on record, respectively. 110 As climate change accelerates in the 21st century, it is anticipated that extreme heat events will become more frequent and intense in California, including Irvine. In Irvine specifically, the projected average number of extreme heat days per year could increase from 4 to 12, assuming global greenhouse gas emissions peak around 2040, then decline. If global greenhouse gas emissions continue to rise until 2100, the number of extreme heat days could increase to as many as 25 days per year. The number of warm nights could increase from 4 to 41 assuming an emissions peak and decline at 2040 but could increase to as many as 86 if emissions continue to rise until 2100. 49 F108 F 111 Heavy Rain Climate change is expected to alter rainfall patterns in southern California, including Irvine. As the climate warms, rain events are predicted to become more intense. It is likely that Irvine will experience more rain inundation events that lead to flooding and erosion, as well as increase the threat of dam failure, tree mortality, and other potential hazards. Severe Wind It is anticipated that the atmospheric rivers that deliver storms to Southern California may intensify as a result of climate change. While the average number of storms in Southern California will remain the same, storms are expected to increase in strength by 10 to 20 percent (Oskin 2014). This increase in storm intensity may also bring more intense winds to the Southern California region, including Irvine. It is not yet known if climate change will affect the frequency or intensity of Santa Ana wind events.

Wildfire

Description

Wildfires are fires that burn in largely undeveloped and natural areas, and they are a regular feature of ecosystems throughout California. These fires help to clear brush and debris from natural areas and are necessary for the health of many ecosystems and the life cycle of various species. However, the common practice since the early twentieth century was to suppress naturally occurring fires in wildland areas, allowing dry plant matter and other fuels to build up. At the same time, human activity has caused changes in the buffer zone between urbanized and undeveloped areas, known as the wildland-urban interface (WUI). The more natural setting of a WUI can make these zones highly desirable places to live, and in many parts of California, the WUIs have become developed, albeit at lower densities than fully urbanized areas. However, this development activity has brought more people into wildfire-prone areas. The availability of fuel and increasing encroachment into the WUI have made wildfires among the most common and dangerous of all- natural hazards in California. From 1950 to 2012, there have been 178 fire emergencies in the state,

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