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Greenville County Hazards

Naturally Occurring Events

Dam/Levee Failure
Dam/levee failure is any destruction or weakening of the structural integrity of a dam/levee resulting in its inability to retain water.

Greenville County has 19 high hazard, and 31 significant hazard dams.

Drought is when moisture loss exceeds precipitation for an extended period of time.

Greenville County is highly vulnerable to drought periods and ranks first in the state for this vulnerability.

While far less common than in other parts of the world, South Carolina has experienced more than 200 minimal earthquakes since 2001. An earthquake is the trembling or shaking of the earth’s surface caused by the sidelong or vertical movement of tectonic plates.  Manifestations include:  ground shock, surface faulting, ground failures (liquefaction and landslides), tsunamis and seiches.  Earthquakes are measured in magnitude (an instrumental measure of vibration to rank sizes) and intensity (a semi-quantitative ranking of damage and effects on people).

Greenville County ranks eighth in the state for this vulnerability.

Epidemic / Pandemic
An epidemic is a contagious disease which spreads rapidly among many individuals at the same time resulting in suffering and/or death.  A pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance multiple continents, or even worldwide.

In Greenville County, flood hazards often result from severe thunderstorms, tropical storms, seasonal rains and other weather related conditions. Riverine flooding occurs when the flow of rainwater runoff is greater than the carrying capacities of the natural drainage systems. “Flash floods” occur where runoff from precipitation collects in a short period of time in an area of steep gradient and may crest within hours after a period of heavy precipitation.

Greenville County’s topography, combined with its humid climate, makes it highly vulnerable to inland or riverine flooding.

Greenville County has experienced over 110 flooding events since 1970 – three significant flooding events occurred between 2003-2005, resulting in more than $11 million in crop and property damage.

Greenville County is highly vulnerable to flooding and ranks first in the state for this vulnerability.

High Winds / Tornado
Tornadoes are violently rotating columns of air that descend in a funnel shape from storm clouds.  The vortex may be several hundred yards in diameter and usually rotate counterclockwise at speeds up to 300 plus miles per hour.  Hailstones reaching sizes sufficient to cause injury to people and structural damage often accompany tornadoes.

The most common type of tornado, the relatively weak and short-lived type, occurs most often between March and May.

Greenville County is ranked fourth in the state for this vulnerability.

Hurricane / Tropical Storm
Although hurricanes are primarily thought of as a coastal phenomenon, inland counties may be directly affected by these storms. Even though Greenville County is over 200 miles inland from the nearest coast, hurricanes can pose a serious hazard including high winds, tornadoes, and inland flooding associated with heavy rainfall.

A Hurricane is a severe tropical storm that exceeds sustained winds near the center of at least 74 miles per hour. Sustained wind speeds may exceed more than 200 miles per hour.  Hurricanes are noted by the spiral rain bands with embedded thunder cells that often produce tornadoes.  Recognized as nature’s most powerful storms, hurricanes produce high winds, storm surge, and flooding from great amounts of rain. 

A Tropical Storm is a weather system characterized by low pressure with strong cyclonic circulation, rain, and wind speeds at least 39 miles per hour, but not more than 73 miles per hour.  Tropical storms produce numerous thunderstorms with strong winds and flooding rain.

Thunderstorms are fast moving squall lines that may produce winds greater than 60 miles per hour and often accompanied by heavy rain, lightening, hail, and tornadoes.  Large thunderstorms may form which produce local downpours, flash flooding, power failure, and fires.

A wildfire is a fire involving forest or grass on publicly or privately owned forest, agriculture lands, and grasslands which are, or could become, a disaster.

Wildfires are caused by numerous sources; lightning, arson, carelessness by smokers, individuals burning debris, equipment which throw sparks, or children playing with matches.

South Carolina experiences more than 5,000 wildfires each year.

Greenville County is ranked twelfth in the state for this vulnerability.

Winter Storms
Winter storms are created by atmospheric disturbances occurring between cold polar and warm tropical air masses, resulting in heavy snow, freezing rain, and ice storms. In our area, ice storms are more common than snow falls. The term “ice storm” is used to indicate ice coating which, because of the weight of the ice may cause significant damage to trees and overhead utility lines.  Damage will be greater if the storm is accompanied by high winds.

Winter storms can damage property, create safety risks, destroy crops and valuable timber, damage infrastructure components such as power lines, and have enormous economic impacts. Both snow and ice can cause major difficulties on roads and highways. Bridges are more likely to freeze before roadways, which can cause a serious driving hazard.

Greenville County is highly vulnerable to winter storms and ranks first in the state for this vulnerability.

Technological Events

Communications Failure 
The severe interruption or loss of private and or public communications systems, including but not limited to transmission lines, broadcast, relay, switching and repeater stations as well as communications satellites, electrical generation capabilities, and associated hardware and software applications necessary to operate communications equipment.  These disruptions may result from equipment failure, human acts, (deliberate or accidental) or the results of natural or human made disasters.

Mass Power Failure 
The loss of commercial power from a public utility company substation, subsidiaries or electric cooperative that effects 1,000 customers for a 24-hour period.

Human Related Events

Civil Disorder
Group acts of violence and disorders prejudicial to public order.  A disruption of essential services.

Civil disorder may occur at anytime in Greenville County. However, civil disorder is often preceded by periods of increased tension caused by questionable social and/or political events such as controversial jury trials or law enforcement actions.

Terrorism is defined at the unlawful use or threatened use of force or violence by a person or an organized group against people or property with the intention of intimidating or coercing societies or governments, often for ideological or political reasons.

Governmental, transportation, commercial, infrastructure, cultural, academic, research, military, athletic events, and industrial facilities constitute potentially-attractive venues for terrorist activities.

Terrorism is not limited to just acts of International terrorist groups; some terror acts can be domestic. From large scale acts of violence to local hostage taking situations, we should always be vigilant to the possibilities around us each day.

Hazardous Materials (HazMat) Events

Fixed Facility (HazMat)
A fixed facility HazMat event is the spillage or release, either intentionally or accidently, of Hazardous Waste or Toxic Materials which may cause death and injury to the populace and damage or destruction to property and the environment.

Greenville County has the largest concentration of facilities reporting Extremely Hazardous Substances (EHS) in South Carolina. The county’s industrial capacity and the network of interstate highways and railways result in vulnerabilities to hazardous material releases from both stationary sites and transportation sources.

Greenville County is highly vulnerable to hazardous materials incidents and ranks second in the state for this vulnerability.

Nuclear Accident (Fixed)
A fixed nuclear accident is an incident that produces significant amounts of radioactive gases and or particles which can be released from the facility.  Effects can range from a minor release to a radioactive release that would force the evacuation of the general population within a ten mile radius of the facility.  Radioactivity from a release may enter the food chain through crops or dairy products out to a fifty mile radius of the facility.  Meteorological conditions can have significant influence on the size of the contaminated area.

Greenville County is within the 50 mile emergency planning zone of the Oconee Nuclear power plant.

Pipeline Accident
A pipeline accident is the spillage or release, either intentionally or accidently, of Hazardous Waste, Toxic Materials, or Natural Gas which may cause death and injury to the public and damage or destruction to property and the environment.

In June of 1996, Greenville County experienced the second largest inland oil spill in U.S. history when 957,600 gallons of fuel oil spilled into the Reedy River.

Transportation (HazMat)
(Chemical) a spill of any of the petroleum family products or chemicals deemed toxic as identified in Department of Transportation Regulations which are a threat to life or property.

(Radioactive) any material or combination of materials which spontaneously emit ionizing radiation.  These materials include Plutonium-238; Plutonium-239; Plutonium-241; Uranium-223; or Uranium-235.

Greenville County has a large transportation network consisting of major highways, airports, and active railroads. These networks present the potential that a major transportation accident causing numerous injuries and/or fatalities may occur.

Greenville County is highly vulnerable to transportation accidents and ranks first in the state for this vulnerability.