Wake County Hazard Mitigation Plan - January 2020


potential is measured by an index that NASA created called the Convective Available Potential Energy (CAPE) index. This measures how warm and moist the air is, which is a major contributing factor in thunderstorm/tornado formation. NASA projects that by the period of 2072-2099, the CAPE in the southeastern United States will increase dramatically. Parts of North Carolina are in an area that will likely experience the greatest increase in CAPE in the United States and all of the state is likely to experience at least some increase. This indicates that there will potentially be even more frequent thunderstorms in the state going forward.

Vulnerability Assessment Methodologies and Assumptions

Population and property at risk to wind events was estimated using data from the North Carolina Emergency Management (NCEM) IRISK database , which was compiled in NCEM’s Risk Management Tool . People People and populations exposed to the elements are most vulnerable to severe weather. A common hazard associated with wind events is falling trees and branches. Risk of being struck by lightning is greater in open areas, at higher elevations, and on the water. Lightning can also cause cascading hazards, including power loss. Loss of power could critically impact those relying on energy to service, including those that need powered medical devices. Additionally, the ignition of fires is always a concern with lightning strikes. The availability of sheltered locations such as basements, buildings constructed using hail-resistant materials and methods, and public storm shelters, all reduce the exposure of the population. Residents living in mobile homes are more vulnerable to hail events due to the lack of shelter locations and the vulnerability of the housing unit to damages. According to the 2017 American Community Survey (ACS) 5- Year Estimates, 12,321 occupied housing units (3.2 percent ) in Wake County are classified as “mobile homes or other types of housing.” Using the 2017 ACS persons per household estimate of 2.62, the population at risk due to their housing type was estimated at 32,281 residents. Individual who work outdoors may also face increased risk. Since 1998, the NCEI records three fatalities and no injuries attributed to lightning in Wake County. NCEI records 2 fatalities and 12 injuries attributed to wind events in Wake County. There are no injuries or fatalities attributed to hail. Property Property damage caused by lightning usually occurs in one of two ways – either by direct damages through fires ignited by lightning, or by secondary impacts due to power loss. According to data collected on lightning strikes in Wake County, the vast majority of recorded property damage was due to structure fires. NCEI records lightning impacts over 17 years (1998-2015), with $2,417,000 in property damage recorded (no incidents were recorded in 2016, 2017, or 2018). Historically, this has resulted in $142,176 in property impacts annually in Wake County. The average impact from lightning per incident in Wake County is $73,242. General damages to property from hail are direct, including destroyed windows, dented cars, and building, roof and siding damage in areas exposed to hail. Hail can also cause enough damage to cars to cause them to be totaled. The level of damage is commensurate with both a material’s ability to withstand hail impacts, and the size of the hailstones that are falling. Construction practices and building codes can help

Wake County Multi-Jurisdictional Hazard Mitigation Plan 2019


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