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III. Risk Assessment <br /> A. Hazard Identification and Analvsis <br /> Orange County,including the Town of Carrboro and the Town of Hillsborough, is vulnerable to <br /> a number of natural hazards. Although each hazard cannot be predicted,they can be less <br /> disruptive to communities with hazard mitigation planning. Each hazard is unique to Orange <br /> County in terms of types, likelihood of occurrence, location, and impact. Each of these terms is <br /> explained below. <br /> 1. Types Of Hazards <br /> Orange County has experienced or could experience many different types of natural <br /> hazards. Some are more likely than others to occur. Different hazards call for different <br /> hazazd mitigation measures. The OCHM Team considered all of the hazards that threaten <br /> Orange County and focused on those that pose the greatest risk. The hazards considered for <br /> this plan were: Hurricanes,Floods,Tornadoes, Droughts and Heat Wave, Nor'easters, <br /> Thunderstorms, Severe Winter Storm,Wildfire,Chemical Spills, River Basins Dam <br /> Failure,Earthquake,Tsunamis, Volcano,Landslide, Plane Crash. <br /> Hurricanes <br /> Because of Orange County's inland location,hurricanes have not historically been a <br /> significant threat. Hurricanes that have reached as far inland as Orange County have <br /> historically been greatly weakened as they neared and passed over the area. Hurricanes are <br /> cyclonic storms originating in tropical ocean waters and fueled by latent heat from the <br /> condensation of wann water. Heavy precipitation,high winds and tornadoes are all <br /> typically associated with hurricanes. <br /> Hurricane intensity is measured using the Saffir-Simpson Scale,ranging from 1 <br /> (minimal)to 5 (catastrophic)based on wind speeds, surface pressure, and height of storm <br /> surge, as shown in the Table below. Major hurricanes are categorized as 3,4,or 5 on the <br /> Saffir-Simpson Scale.While hurricanes within this range comprise only 20°10 of total <br /> tropical cyclone landfalls,they account for over 70°Io of the damage in the United States. <br /> Maximum sustained winds of category 3,4 and 5 hurricanes range from 112 mph to over <br /> 156 mph. This wind intensity topples trees and causes severe damage to structures. <br /> Saffir-Sim son Hurricane Scale(Sim son and Reihl 1981) <br /> Saffir-Simpson Maximum Sustained Minimum Surface Height of Storm <br /> Cate or Winds(m h) Pressure(mb) Sur e(in feet) <br /> 1 74-96 >980 3-5 <br /> 2 97-111 979-965 6-8 <br /> 3 112-131 964-945 9-12 <br /> 4 132-155 944-920 13-18 <br /> 5 156+ <920 19+ <br /> Source:North Carolina Division of Emergency Management, 1998:Local Hazard Mitigation Planning Manual. <br /> 7 <br />