BEAUFORT HAZARD MITIGATION PLAN 2009 UPDATE for Unincorporated Beaufort County The City of Beaufort The Town of Bluffton The Town of Hilton Head Island The Town of Port Royal Prepared by: Lowcountry Council of Governments Planning Department December 2009 Hazard Mitigation Plan i Beaufort County, South Carolina TABLE OF CONTENTS 1. Introduction ...................................................................................................... 1-1 Background ................................................................................................................... 1-1 Planning Process .......................................................................................................... 1-2 Getting Organized ....................................................................................................................... 1-2 Committee ............................................................................................................................................ 1-3 Assess Hazards and Vulnerabilities ........................................................................................... 1-4 Develop a Mitigation Plan ........................................................................................................... 1-5 Other Agencies ..................................................................................................................................... 1-6 Evaluate Your Work .................................................................................................................... 1-7 Public Involvement ...................................................................................................................... 1-7 Federal Funding Sources for Mitigation ......................................................................... 1-7 2. Hazard Identification and Profiles .................................................................... 2-1 Introduction ................................................................................................................... 2-1 Hurricanes, Tropical Storms .......................................................................................... 2-1 Past Occurrences of Hurricanes ................................................................................................. 2-1 September 1804 ................................................................................................................................... 2-4 August 1854 ......................................................................................................................................... 2-4 August 1893 ......................................................................................................................................... 2-4 October 1902 ........................................................................................................................................ 2-5 August 1940 ......................................................................................................................................... 2-5 October 1944 ........................................................................................................................................ 2-5 Hurricane Cindy – July 1959 ................................................................................................................. 2-5 Hurricane Gracie - September 1959 ..................................................................................................... 2-5 Hurricane Donna – September 1960 .................................................................................................... 2-6 Hurricane David – September 1979...................................................................................................... 2-6 Hurricane Bob – July 1985 ................................................................................................................... 2-6 Hurricane Hugo – September 1989 ...................................................................................................... 2-6 Future Probabilities of Hurricanes ............................................................................................... 2-7 Past Occurrences of Nor’Easters................................................................................................ 2-8 Flooding ........................................................................................................................ 2-9 Past Occurrences of Flooding ................................................................................................... 2-12 Future Probabilities of Flooding ................................................................................................ 2-12 Erosion ........................................................................................................................ 2-18 Past Occurrences and Future Probabilities of Erosion ............................................................. 2-16 Winter Storms ............................................................................................................. 2-20 Past Occurrences of Winter Storms.......................................................................................... 2-20 Future Probabilities of Winter Storms ....................................................................................... 2-21 Dam Failure ................................................................................................................. 2-33 Drought ....................................................................................................................... 2-21 Wind: Thunderstorms and Tornadoes ......................................................................... 2-22 Past Occurrences of Thunderstorms ........................................................................................ 2-22 Future Probability of Thunderstorms......................................................................................... 2-22 Tornadoes ................................................................................................................... 2-22 Past Occurrences of Tornadoes ............................................................................................... 2-24 Future Probabilities of Tornadoes ............................................................................................. 2-26 Hazard Mitigation Plan ii Beaufort County, South Carolina Earthquakes ................................................................................................................ 2-27 Past Occurrences of Earthquakes ............................................................................................ 2-28 Earthquakes near Beaufort County: potentially a major impact. .............................................. 2-28 1886 Earthquake ................................................................................................................................ 2-29 Future Probabilities of Earthquakes .......................................................................................... 2-30 Fire .............................................................................................................................. 2-30 Past Occurrences of Fire .......................................................................................................... 2-31 Future Probabilities of Fire Community/ Public Affairs Manager, Community/ ......................... 2-33 Hazards not Historically Prevalent ............................................................................... 2-33 Landslides ................................................................................................................................. 2-33 Tsunamis ................................................................................................................................... 2-34 Volcanic Hazards ...................................................................................................................... 2-34 3. Vulnerability Assessment ............................................................................... 3-36 Vulnerability Summary ................................................................................................ 3-36 Social Vulnerability ...................................................................................................... 3-39 Inventory Information ................................................................................................... 3-40 Flooding ...................................................................................................................... 3-42 Floodplain .................................................................................................................................. 3-42 Flood Depths ...................................................................................................................................... 3-42 City of Beaufort ................................................................................................................................... 3-42 Town of Bluffton .................................................................................................................................. 3-43 Town of Hilton Head ........................................................................................................................... 3-43 Town of Port Royal ............................................................................................................................