IV. Risk Assessment

Risk assessment is the process of measuring the potential loss of life, personal injury, economic injury, and property damage resulting from natural or man-made hazards. The results of this risk assessment assist Jefferson County and its incorporated municipalities in identifying and understanding their risks from natural and man-made hazards. This information also serves as the foundation for the development of the mitigation plan and strategies to help reduce risks from future hazard events.

This risk assessment followed the methodology described in the FEMA publication 386-2 “Understanding Your Risks – Identifying Hazards and Estimating Losses” and was based on a four-step process: 1) Identify Hazards, 2) Profile Hazard Events, 3) Inventory Assets, and 4) Estimate Losses. Using FEMA guidance, as well as the Section 322 regulations for developing local hazard mitigation plans EK has developed a risk assessment that identifies:

¨ The hazards to which the county and its communities are susceptible.

¨ The impact of these hazards on physical, social, and economic assets.

¨ The areas within the county most vulnerable to these hazards.

¨ The potential costs of damages or costs avoided through future mitigation projects.

A. Hazard Identification

The first step in the risk assessment process was to identify each of the hazards that can occur within Jefferson County and its incorporated municipalities. This hazard identification process began with a review of previous hazard events based on historical data provided by the Jefferson County Emergency Manager, Darrell Penwell, and the Jefferson County Project Impact Coordinator, Barbara Miller. EK also conducted a review of existing resources, plans, and reports provided by FEMA, Jefferson County, and other sources to understand the nature and extent of natural and man-made hazards in the county (see Appendix B). In addition to these resources EK also conducted hazard identification and prioritization exercises with the members of the Core Planning Team and the members of the Jefferson County Project Impact Partnership (see Appendix A). The findings from these steps were utilized to determine the priority hazards for Jefferson County and its municipalities, which will become the focus of the mitigation strategies developed in the remainder of this plan.

1. Hazard History

Past occurrences of hazard events are likely predictors of future events. A review of the hazard history of Jefferson County, therefore, helps to provide a better understanding of what hazards the county is susceptible to. Detailed descriptions of the historic hazard events, including information on losses of life and property, as well as estimated damages are included in the Appendix. Below are summaries of the major events by hazard type based on information that was available during the development of this plan.

Flood

The worst hazard events experienced in Jefferson County were incidences of flooding resulting from heavy rains, snow melt, and coastal storms. The earliest flood on record occurred in 1870 when the Shenandoah River was recorded at 12.9 feet above flood stage in the community of Millville. The most damaging floods in Jefferson County have all occurred within the last decade.

§ October 1962: Flooding of the Shenandoah River at Millville resulted in estimated damages to over 40 homes and mobile homes. The river crested at 32.45 feet.

§ April 22, 1992: Both the Shenandoah and the Potomac rivers crested above flood stage after 4.5 inches of rainfall. A car and a mobile home were destroyed by the high waters.

§ March 25-28, 1993: Flash flooding occurred after snow melted throughout the county. Several people were evacuated and approximately $5,000 in damages to public facilities was caused.

§ January 19-21, 1996: A three-day period of flooding resulting from snow melting after the Blizzard of 1996. Several roads were closed and many structures were affected or damaged by high water. This flooding resulted in approximately $593,000 in damages to public and private facilities.

§ September 6, 1996: Heavy rain and flooding was experienced as a result of Hurricane Fran. Damage was sustained by many residential structures throughout the county. Harpers Ferry was especially hard hit with the flooding of park exhibition buildings and clean-up costs of over $2.8 million. Transportation was also impacted with roadways closed and washed out as well as severe damage to some CSX tracks.

§ November 7-10, 1997: Flooding on the Potomac River, Opequon Creek, and the Shenandoah River resulted in the inundation of roadways and other minor damages.

§ January 8-10, 1998: Roadways flooded with minor damages reported. The Opequon Creek crested .75 inches above flood stage; Potomac River crested 1/2 foot under flood stage; and the Shenandoah River crested 1.8 feet over flood stage at Millville.

§ January 28-29, 1998: Flooding occurred along the Shenandoah and Potomac Rivers and the Opequon Creek banks during a Winter Storm Warning issued by the National Weather Service.

Winter Storm

The worst winters storms of record in Jefferson County have also occurred within the last decade. Severe winter storms are common in this part of the state due to its extreme northeastern location and proximity to higher elevations.

§ March 13, 1993: A winter storm resulted in road closures and damages to 25 structures. School and government facilities were also forced to close. There were five reported injuries and an estimated $30,000 of damages to public facilities.

§ January 6-13, 1996: The Blizzard of 1996 produced 22-40 inches of snow throughout the county, gale-force winds, and 5-8 foot snow drifts. Power outages, felled trees, and blocked roads were also reported.

§ December 11, 2002: An ice storm with freezing rain caused damages countywide including downed trees, power and other utilities cables and poles, and the disruption of power for over 4,000 customers.

§ February 2003: Severe winter storm with high amounts of snowfall and ice accumulation causing power outages and structure damages. Preliminary damage assessments are still being calculated.

Tornado

Jefferson County has experienced two recorded incidences of tornado touchdowns. The most recent tornado occurred in 1989 and neither event resulted in any deaths.

§ August 26, 1965: A category F1 tornado with wind speeds between 73 and 112 mph was reported in Jefferson County by the National Weather Service.

§ November 16, 1989: A category F2 tornado with winds speeds ranging from 113-206 mph created a 4-mile damage path that was 100 yards wide. Several accessory buildings were damaged and one mobile home was destroyed. Three people reported injuries and the county suffered an estimated $100,000 in private property damages.

§ July 2, 1997: A severe thunderstorm and tornado event caused heavy rains and other damages in the southwestern portion of the county that lead to four injuries. The tornado struck a large block warehouse building at the Burch’s Box Factory. Rains also caused roadway flooding and a portion of Cattail road was washed out. The total damages from this event were $250,000.

Wind Storm

Jefferson County has also experienced high windstorms not associated with tornado events. According to the materials provided by the Jefferson County Project Impact Coordinator, the county has experienced two high wind events within the last five years.

§ July 21, 1998: A windstorm damaged an electric power substation in Millville causing power outages in Millville, Shepherdstown, and Bolivar.

§ April 28, 2002: High winds reported at the Charlie Adams farm in Rippon.

Severe Thunderstorm

According to the records provided by the Jefferson County Emergency Manager for this risk assessment, Jefferson County has experienced at least one severe thunderstorm event.

§ July 24, 1999: A severe thunderstorm with winds over 50 mph resulted in damage to trees and the loss of power for approximately 1,000 customers.

§ August 14, 2002: A sever thunderstorm with winds over 40 mph caused damage to trees and minor power outages.

§ April 9, 2002: A severe thunderstorm event resulted in strong winds and lightning strikes that caused power outages, felled trees, a field fire, and minor structural damages.

Technological Hazards

Jefferson County has experienced one recent technological hazard event involving the transportation of hazardous materials.

§ February 28, 2003: A tanker carrying 2,000 gallons of propane overturned causing a release of the chemical into the environment. Nine residences within a quarter-mile of the accident site were evacuated. Summit Point road was also closed for a mile in either direction for three hours while the propane leak was contained and the vehicle was cleared from the roadway. The tanker driver suffered minor injuries.

2. Priority Hazards

The historical hazard information provided insight into some of the high priority hazards that should be included in the plan; however, it did not capture all of the possible hazard risks in the county and municipalities. An additional review of possible hazard risks was conducted using the resources provided in “Understanding Your Risks – Identifying Hazards and Estimating Losses” (FEMA 386-2). Based on this review earthquake, landslides, land subsidence, and wildfires were identified as potential threats in Jefferson County. The rationale for selecting these hazards is described in greater detail below.

Additional hazards were also identified and prioritized through an exercise that was conducted with the Core Planning Team and the Jefferson County Project Impact Partnership. In both exercises the participants were asked to identify natural and man-made hazards that occur in Jefferson County and rank the selected hazards from highest to lowest priority. The results of those exercises are included in Appendix A of this document. The table below provides a summary of how the priority hazards were determined using a combination of historical occurrences, public perception of hazard risk, and the probability of future occurrence based on other technical resources.

Table 4. Prioritization of Hazards for Jefferson County

Key: H= High, M=Moderate, L=Low, N/A = Not Applicable, Unknown = Historic Data Unavailable, OES = Jefferson County Office of Emergency Services, NWS = National Weather Service, FEMA = Federal Emergency Management Agency, USFS = United States Forestry Service, USGS = United States Geologic Survey

Based on these findings and the results of technical research the following hazards were selected as priority hazards for Jefferson County: Floods; Severe Winter Storms; Severe Thunderstorms/ Lightning; Windstorms; Tornadoes; Drought; Hailstorms; Wildfires; Earthquakes; Landslides; Land Subsidence; Technological Hazards; Fires; and Terrorism.

B. Profile of Hazard Events

The second step in the risk assessment process was to create a profile of each of the priority hazards in Jefferson County. This analysis assisted in determining the potential damages in the county from natural and man-made hazards. This portion of the risk assessment was done through the use of Geographic Information Systems (GIS) software to develop maps that show the geographic locations for some of the priority hazards. Maps were developed for flooding, landslide, earthquake, land subsidence, and technological hazards using existing data and maps provided by the Jefferson County Project Impact Coordinator. The remaining priority hazards are described in narrative form due to data limitations or an inability to map the geographic extent of the hazards.

1. Mapped Hazards

Floods

Flooding is defined as a general and temporary condition of partial or complete inundation of normally dry land areas from: the overflow of inland or tidal waters; the unusual and rapid accumulation or runoff of surface waters from any source; or mudflows or the sudden collapse of shoreline land. Flooding is arguably the highest priority natural hazard in Jefferson County. This is largely due to the physical geography of the county, which includes several rivers and creeks as well as a varied topography.

Located at the confluence of the Potomac and Shenandoah Rivers, Jefferson County is separated into three major drainage divides by the County’s rolling topography. The Shenandoah River has a drainage area of 247 square miles at the downstream county boundary. Its average channel slope within Jefferson County is approximately 4.6 feet per mile. Between these drainage divides are a network of 22 major streams that feed into the two aforementioned rivers and Opequon Creek. Opequon Creek has a drainage area of 8.0 square miles and an average channel slope of approximately 56 feet per mile. Most streams in the County flow in a northwest-southeast orientation toward the Opequon or Shenandoah. Turkey Run, one of the largest streams, has a total drainage area of 8.0 square miles and its average channel slope within Jefferson County is approximately 50 feet per mile. Evitts Run, another large stream, has a drainage area of 17.91 square miles. Its headwaters are in central Jefferson County and flows eastward to the Shenandoah River. Flowing Springs Run, an additional large stream, has a drainage area of 7.88 square miles. It heads just north of Ranson and flows eastward to the Shenandoah River. Almost all of these streams are spring fed, thus resulting in the intermingling of surface and subsurface waters. Regardless of their origin, all waters ultimately flow into the lower Potomac River and the Chesapeake Bay.

Identification of floodplain areas within the county and the incorporated municipalities was based on the most recent Flood Insurance Rate Maps (FIRM) produced by FEMA. Map 1, titled “Flood Hazard Areas” and located at the end of this section of the plan, displays the locations of all of the major water bodies in the county and delineates the 100-year floodplain boundaries (Zone A). These are areas that have a one percent chance of equaling or exceeding the recorded base flood elevation during any year. Based on this map four out of the five incorporated municipalities have 100-year floodplains within their jurisdictions. Bolivar is the only municipality without a designated floodplain within its boundary. While Bolivar may not have a mapped floodplain according to FEMA it is not completely without flooding problems. According to the Bolivar Comprehensive Plan nuisance flooding impacts many roads due to poorly designed and maintained drainage systems. Map 1 also shows several areas in the unincorporated portions of the county where 100-year floodplains have been identified.

Land Subsidence

The term land subsidence (commonly named sink-holes) refers to any failures in the ground that cause collapses in the earth’s surface. Land subsidence can be caused by natural processes, such as the dissolving of limestone underground, an earthquake, or volcanic activity. It can also be the result of human actions such as withdrawal of subsurface fluids or underground mining. Approximately 86% of Jefferson County lies on a geologic formation known as karst, which is prone to sink holes, a type of land subsidence. Comprised predominantly of fractured limestone, this formation covers most of the county between the Shenandoah River and Opequon Creek. Topographically, this formation is characterized by fertile soils and sinkholes that are created when the carbonate rock beneath is eroded by subsurface water to the point where the structure collapses, creating a crater on the land surface. This formation is very porous and allows for the transmission of liquid from the surface of the soil to the aquifer below, which provides most residents with their drinking water.

In Jefferson County the presence of limestone geology, underground water sources, and several underground caves increases the possibility of sink holes and land subsidence. Areas that are potentially susceptible to land subsidence are indicated in Map 2 titled “Land Subsidence Hazard Areas” located at the end of this section. Potential land subsidence areas were determined based on the location and size of caves throughout the county. Cave location information was obtained through studies developed by the West Virginia Geological Survey as well as local cave enthusiasts (see Appendix B – Resources for more information). Using latitude and longitude information provided in these studies EK was able to map each of the recorded cave entrances. Several of the limestone caves are located near Shepherdstown, Bolivar, Harpers Ferry, and Charles Town as well as other locations in the unincorporated portions of the county including along the Opequon Creek and the Shenandoah River.

To determine the area of potential risk surrounding the caves GIS was used to create an area of risk around the cave entrances. The recorded maximum horizontal length of the cave determined the size of each area of risk. To this extent the areas of risk include more land than may actually be at risk from land subsidence. A more detailed geologic study of the areas above the caves would be required in order to truly determine the level of land subsidence risk in these areas, which was not included in the scope of this work.

Landslide

Landslides are defined as any downward movement of a slope and materials under the force of gravity. The term landslide includes a wide range of ground movement, such as rock falls, deep failure of slopes, and shallow debris flows. Landslides are influenced by human activity (mining and construction of buildings, railroads, and highways) and natural factors (geology, precipitation, and topography). Landslides occur when masses of rock, earth, or debris move down a slope. Therefore, gravity acting on an overly steep slope is the primary cause of a landslide. Storms, fires, or human modifications to the land typically activate landslides.

A review of a national landslide hazard map produced by the United States Geologic Survey (USGS) was used to identify landslide risks in Jefferson County. Information from USGS was used to produce an overlay in GIS for Jefferson County that describes the level of landslide risk throughout the county and is depicted in Map 3 “Landslide Hazard Areas” at the end of this section. According to this analysis the southeastern corner of Jefferson County has the highest landslide risk. The remainder of the county is characterized as either a medium or low landslide risk. The communities of Harpers Ferry, Bolivar, Charles Town, and Ranson fall in the medium landslide risk category, whereas Shepherdstown is considered a low landslide risk area. The level of detail of Map 3 provides a general understanding of landslide hazard risks in Jefferson County for planning purposes. As the topography and underlying geology have the greatest influence as to whether a landslide will occur and additional studies would be required to determine the actual vulnerability to structures at individual sites within the high or medium risk areas.

Earthquake

An earthquake is a sudden motion or trembling that is caused by a release of strain accumulation within or along the edge of Earth’s tectonic plates. The severity of these effects is dependent on the amount of energy released from the fault or epicenter. The effects of an earthquake can be felt far beyond the site of its occurrence. Earthquakes usually occur without warning and after just a few seconds can cause massive damage and extensive casualties. Common effects of earthquakes are ground motion and shaking, surface fault ruptures, and ground failure.

Peak ground acceleration (PGA) is a measure of the strength of ground movements. The PGA measures the rate in change of motion relative to the established rate of acceleration due to gravity. Based on the national map provided by the USGS (Figure 1)[1] that shows the PGA values for areas with a 10% chance of being exceeded over 50 years the entire state of West Virginia has an earthquake risk as it is located in the 3%g area. According to FEMA, areas with a 3%g PGA or more are considered to have a moderate to high earthquake hazard risk and should consider earthquake hazards when developing hazard mitigation plans. In Jefferson County, however, the earthquake risk is relatively low compared to other portions of the state or even the country.

Map 4, “Earthquake Hazard Areas”, shows the best available earthquake hazard data for Jefferson County and is based on maps created by the West Virginia University GIS Tech Center. This map shows the locations of the fault lines in the county as well as the underlying geology that may influence the likelihood of an earthquake in the future. Proximity to faults, along with soil and subsurface characteristics, can all affect the level of earthquake hazard. It is important to note however the proximity of Jefferson County to other areas of earthquake activity. The Central and Southeast U.S. region covers a large area of relatively diffuse, low rate seismicity. Principal areas of activity include the New Madrid Seismic Zone, East Tennessee, and Southern Appalachian Seismic Zones, and South Carolina. These factors increase the likelihood of Jefferson County experiencing or being affected by an earthquake at some point in time even though there is no historical evidence of earthquakes occurring in the past.

Technological Hazards

The term technological hazard refers to the origins of incidents that can arise from human activities such as the manufacture, transportation, storage, and use of hazardous materials. For the purposes of this risk assessment it is assumed that technological emergencies are accidental and that their consequences are unintended.

Hazardous materials incidents typically take two forms, fixed facility incidents and transportation incidents.  The major difference between the two is that it is reasonably possible to identify and prepare for a fixed site incident, because laws require those facilities to notify state and local authorities about what is being used or produced there.  Transportation incidents are substantially harder to prepare for, however, because it is difficult to determine what material(s) could be involved until the accident actually happens. 

In order to profile the technological hazards in Jefferson County information was compiled on the locations of facilities that store hazardous materials. Based on records provided by the Jefferson County Office of Emergency Services there are 98 facilities in the county that store hazardous materials, 14 of which are facilities that store extremely hazardous substances (EHS). Map 9, “Technological and Man-Made Hazards” shows the locations of these facilities across the county. A complete listing of the facilities is also included in Appendix G of this document.

Terrorism

The term terrorism refers to intentional criminal and malicious acts. For the purposes of this risk assessment terrorism refers to the use of Weapons of Mass Destruction (WMD), including, biological, chemical, nuclear, and radiological weapons; arson, incendiary, explosive, and armed attacks; industrial sabotage and intentional hazardous materials releases; and cyber terrorism. Due to the sensitive nature of the information compiled for the analysis of terrorism threats a separate annex containing maps and mitigation strategies for terrorism was developed to accompany this plan. At this time that annex is not available for public viewing and is restricted to members of the county and municipal emergency management, public safety, and law enforcement agencies.

Multiple Hazard Areas

For the purposes of analysis a composite hazard map was developed that illustrates the areas of the county that are subject to more than one of the previously described mapped hazards. Map 5 “Multiple Hazard Areas” located at the end of this section shows the areas in the county that suffer from the presence of more than one hazard. According to this analysis there are only three multiple hazard incidences in Jefferson County, all of which occur in the unincorporated portions of the county. Two incidences are areas that suffer from both flooding and potential land subsidence and the final area is a combination of high landslide risk and flooding.

2. Non-Mapped Hazards

Severe Winter Storm

Winter storms vary in size and strength and can be accompanied by strong winds that create blizzard conditions and dangerous wind chill. There are three categories of winter storms. A blizzard is the most dangerous of all winter storms. It combines low temperatures, heavy snowfall, and winds of at least 35 miles per hour (mph), reducing visibility to only a few yards. A heavy snowstorm is one that drops 4 or more inches of snow in a 12-hour period. An ice storm occurs when moisture falls and freezes immediately upon impact. For the purposes of this risk assessment, it is assumed that all of Jefferson County is equally at risk from severe winter storm events.

Severe Thunderstorms/Lightning

A severe thunderstorm as defined by the National Weather Service is a storm with hail equal to or greater than 3/4" in diameter or convective wind gusts equal to or greater than 58 mph. Lightning and general thunderstorm wind gusts pose a threat to life and/or property. Severe thunderstorms also have the potential of producing a tornado with little or no advanced tornado warning. Based on historical evidence it is assumed that all of Jefferson County is equally at risk from severe thunderstorm events.

Windstorms

For the purposes of this risk assessment windstorms are destructive wind events that occur with or without the presence of other storm events, such as tornados or severe thunderstorms. Localized geographic conditions can exacerbate the damages from high winds and cause increases in wind intensity. Jefferson County has experienced high wind damages in the past and can expect wind-related problems in the future. This assessment assumes that the risks from high wind events are equally distributed throughout the county.

Tornadoes

A tornado is a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of 1 mile wide and 50 miles long. Tornadoes are among the most unpredictable of weather phenomena. Tornadoes can occur in any state in the U.S. but are more frequent in the Midwest, Southeast, and Southwest.

The nature of tornadoes is they strike at random. While it is known that some areas of the country experience tornadoes more than others, predicting exactly what parts of Jefferson County have a greater chance of being struck by a tornado is difficult. The best predictor of future tornadoes is the occurrence of previous tornadoes. According to county records there have been at least two recorded tornado events in Jefferson County. These tornadoes were characterized as an F1 and F2 on the Fujita Tornado Measurement Scale, which categorizes tornadoes based on wind speed and expected damages. An F1 tornado is considered a moderate tornado with wind speeds ranging from 73 to 112 mph and can cause damages such as moving cars off roads and mobile homes off of foundations. An F2 tornado is a significant tornado with wind speeds from 113 to 157 mph a can cause considerable damages such as torn off roofs and uprooted trees.

For planning purposes it is less important to map the tornado risk than it is to identify it. This is because it is so difficult to predict the path of future tornadoes. The Fujita scale provides us with an idea of the strength and extent of damages of tornadoes that can occur in Jefferson County. An additional resource to help understand the extent of tornado risks is the “Design Wind Speed Map” developed by the American Society of Civil Engineers (ASCE). According to this map the entire state of West Virginia is located in Zone III, which is an area associated with up to 200-mph wind speeds.

Drought

Drought refers to an extended period of deficient rainfall relative to the statistical mean for a region. Drought can be defined according to meteorological, hydrological, and agricultural criteria. Meteorological drought is qualified by any significant deficit of precipitation. Hydrological drought is manifest in noticeably reduced river and stream flow and critically low groundwater tables. The term agricultural drought indicates an extended dry period that results in crop stress and harvest reduction.

The Palmer Drought Severity Index (PDSI) is a widely used measure of drought in the United States to track moisture conditions. The PDSI is defined as “an interval of time, generally in months or years in duration, during which the actual moisture supply at a given place rather consistently falls short of the climatically expected or climatically appropriate moisture supply”. The range of PDSI is from –4.0 (extremely dry) to +4.0 (excessively wet), with the central half (-2.0 to +2.0) representing the normal or near normal conditions.

For the purposes of this risk assessment it is assumed that Jefferson County has a moderate drought risk even though there are no recorded instances of drought historically. The risk of drought is not targeted to any particular areas within the county.

Hailstorms

Hailstorms occur when freezing water in thunderstorm type clouds accumulates in layers around an icy core. Hail causes damage by battering crops, structures, automobiles, and transportation systems. When hailstorms are large (especially when combined with high winds), damage can be extensive. Based on available data at the state level it is assumed that the entire county is at moderate risk from hailstorms.

Wildfires

A wildfire is an uncontrolled fire spreading through vegetative fuels, exposing and possibly consuming structures. They often begin unnoticed and spread quickly and are usually signaled by dense smoke that fills the area for miles around. Naturally occurring and non-native species of grasses, brush, and trees fuel wildfires.

Wildfire maps do not show the extent or range of where a wildfire will occur because they are dependent on the amount of fuel available, weather conditions, and wind speed and direction. As there is no historical record of wildfires in Jefferson County this assessment does not map previous locations of wildfires as a determinant for future wildfire events. Based on available data at the state level it is assumed that the entire county is at moderate risk from wildfires.

Urban Fires

An urban fire is any instance of uncontrolled burning which results in major structural damage to residential, commercial, industrial, institutional, or other properties in developed areas. Municipalities with significant development in either a downtown area or an industrial park are prime targets for this type of occurrence. For the purposes of this risk assessment urban fire hazards will be considered moderate for the incorporated municipalities of the county.

C. Vulnerability Assessment

The vulnerability assessment uses the hazard profile information and combines it with community asset information to analyze and quantify potential damages from future hazard events. This process combines the final two steps of the risk assessment: the inventory of assets and the estimation of losses.

1. Asset Inventory

The asset inventory identifies buildings, roads, and other facilities that can be damaged or affected by the hazard events. In order to assess where and to what extent the identified hazards will affect the assets of Jefferson County the locations of assets were identified and intersected with the mapped hazards in GIS.

The information source used to compile the asset inventory was the E-911 database and maps created by MSAG as part of the Jefferson County E-911 readdressing project. This project assigned street addresses to all structures and located them on maps in relation to identified roadways in the county. These maps were used as base maps for the purposes of this risk assessment.

The structures from the E-911 database were then intersected with each of the mapped hazard layers in order to determine the number and location of structures at risk from hazards. According to the E-911 database there are 17,584 structures throughout the county. Also taken from the E-911 database was the location of infrastructure including roadways, railroads, and utilities, which were also intersected with hazard data in GIS to determine vulnerability. Using the data supplied by the Jefferson County Office of Emergency Services, the West Virginia State Police, and local law enforcement maps were developed to show the locations of critical facilities. Critical facilities are defined as facilities that are critical to the health and welfare of the county and that are especially important following hazard events. Critical facilities include, but are not limited to, shelters, police and fire stations, and hospitals. According to this data there are 81 critical facilities in Jefferson County. The complete list of critical facilities in Jefferson County is included in Appendix D of this document. Historical sites are also included in the asset inventory and a complete listing of the sites is located in Appendix E.

Flood

The assets within Jefferson County that are located within the 100-year floodplain are displayed in Maps 6 through 6E. On the map the floodplains are defined with light blue and the structures within them are indicated by red. Map 6 “Structures in Flood Hazard Areas” shows the location of 249 properties within the floodplain in the unincorporated portion of the county such as Leetown, Browns Corner, and Kabletown, as well as the subdivision of Happy Creek. At the county level there are also several critical facilities located within the floodplain, which are labeled and shown on Map 6.

Maps 6A through 6D are larger scale maps that show the inventory of properties located in the floodplain in the municipalities of Charles Town (Map 6A), Harpers Ferry (Map 6B), Ranson (Map 6C), and Shepherdstown (Map 6D). Bolivar was not included because according to FEMA there are no 100-year floodplains within the town. Table 5 below summarizes the asset inventory for properties in the floodplain across Jefferson County.

Table 5. Inventory of Properties Located in Flood Hazard Areas in Jefferson County

Based on this analysis Ranson has the greatest number of properties within the floodplain in Jefferson County. An estimated 61 residential properties located in the southwest portion of the municipality, primarily to the west of George Street, all fall within the identified flood hazard areas

The second highest amount of properties in the floodplain occurs in Shepherdstown where 54 properties are at risk from flooding. These are properties that are alongside of Town Run, a creek that runs through the center of the town from north to south. High Street to the north, New Street to the south, Church Street to the west, and Mill Street to the east bound the area most impacted by this floodplain. Shepherdstown has a mix of both residential and commercial properties at risk from flooding as well as other buildings such as properties belonging to the town and Shepherd College.

Charles Town has the third highest amount of properties in the floodplain at 15. Of these, 2 are commercial and 12 are residential. These structures are primarily located along Evitts Run, a creek that crosses through the southwestern portion of the town, and the majority is in the area surrounding the Evitts Run Park. Charles Town is also the only municipality within Jefferson County to have a critical facility located within the floodplain, the Charles Town Waste Water Treatment Plant.

Based on the existing FIRM maps and the E-911 database only 3 structures within Harpers Ferry are located within the 100-year floodplain all of which are located in the Harpers Ferry National Historical Park. Interviews with town representatives indicate that Harpers Ferry has experienced some of the worst flooding within Jefferson County and many structures have received damages in the past. The inaccuracy of the FIRM maps used to delineate the floodplain in this area may account for the lower than expected structure count. GIS maps from the National Park Service that contain more updated studies of the location of floodplains in Harpers Ferry were also reviewed, however, this information did not lend any insight to the flood problem outside of the park boundaries.

According to information collected by the National Park Service, the lower town of Harpers Ferry has reached or surpassed the flood stage of 18.5 feet over 36 times. The highest river crest of record for the Harpers Ferry area was 36.5 feet on March 19, 1936. Based on the procedures detailed in the Emergency Response Plan for the Harpers Ferry National Historical Park a variety of park and town facilities are at risk when the river crests above flood stage:

§ 16 – 18 ft.: Pedestrian bridge over Potomac River

§ 18.5 – 20 ft.: Shenandoah Street and Harpers Ferry/Bolivar Public Service District

§ 20 – 27 ft.: Lower town

Interviews with local government officials in Harpers Ferry provided further insight to the flooding problem experienced by the town. Based on previous flood events when water rise above 23 feet in Harpers Ferry, the first two buildings on Potomac Street outside of the National Park property are inundated with water. If the floodwater rise to 25 feet the remaining properties on Potomac Street are flooded including a 6 commercial establishments and one residential property.

Infrastructure layers were also intersected with floodplain data across the county to determine the location and amounts of vulnerable roadways, railroads, and utilities. Map 6E “Infrastructure in Flood Hazard Areas” displays this information. The table below summarizes the findings of this portion of the analysis. These results indicate that approximately 29 miles of infrastructure are located in flood hazard areas.

Table 6. Inventory of Infrastructure Located in Flood Hazard Areas in Jefferson County

Facility Type	Number of Miles
Roads	4.47
Utilities	3.38
Railroads	21.39
Total	29.24

The asset inventory for flood hazard areas also included a survey of historical sites located within the floodplain. Only three historic sites are located within the floodplain (shown in Map 6) and all are located in the unincorporated portion of the county. At this time it is unknown whether the three floodplain properties in Harpers Ferry are considered historic sites.

Land Subsidence

Assets that were at risk of land subsidence were determined based on the intersection of the E-911 structure data with the land subsidence risk areas. Properties located within land subsidence risk areas occurred in Charles Town and some portions of the unincorporated county as shown in Map 7 “Structures in Land Subsidence Hazard Areas”. According to this analysis 187 residential and 21 commercial properties were located in land subsidence areas across the county. In Charles Town there were five properties located in the land subsidence risk area classified as “other” uses, all of which are critical facilities (Jefferson County Judicial Center, Charles Town Police Department, and Charles Town Maintenance Department). The other three had no use information. There are no historic sites located in land subsidence risk areas.

Table 7. Inventory of Properties Located in Land Subsidence Hazard Areas in Jefferson County

Use Type	Charles Town	Unincorporated	Total County
Commercial	17	0	17
Residential	1	186	187
Other	3	0	3
Total	21	186	207

The only infrastructure located in land subsidence risk areas across the county are railroads, as indicated in Map 7A “Railroads in Land Subsidence Hazard Areas”. Approximately 0.33 miles of railroad track is located in the land subsidence risk area to the northwest of Bolivar.

Landslides

Using the landslide hazard map developed for Jefferson County and the E-911 data the two maps were overlaid to indicate where structures exist in relation to landslide risk. Results indicate that there are 184 residential properties in the unincorporated portion of the county that are located within the high landslide risk area. Also contained within this area is one critical facility, a microwave tower at Bluemont owned by MCI that provides communications services. There are no commercial properties or historic sites located in high landslide risk areas. Map 8 “Structures in Landslide Hazard Areas” shows the locations of the properties and critical facility in the high-risk area.

Table 8. Inventory of Properties Located in High Landslide Risk Area in Jefferson County

Use Type	Number of Properties
Commercial	0
Residential	184
Other	1
Total	185

The amount of structures contained within the landslide hazard risk may capture more or less structures than are actually at risk from landslides. In order to accurately capture landslide risks in these areas a more detailed assessment would need to be conducted that would consider the soils, land cover, and slopes at each site.

Technological Hazards

Map 9, “Technological and Man-Made Hazards”, shows the locations of facilities that store hazardous materials or extremely hazardous materials and their locations throughout the county. Hazardous materials are any substance or material that when involved in an accident and released in sufficient quantities, poses a risk to public health, safety, or property. Sites included in this map are based on data that was made available by the Jefferson County Office of Emergency Services and Local Emergency Planning Committee (LEPC). There are approximately 50 sites located in the county that store hazardous materials. Out of the 50 sites, 14 facilities store extremely hazardous substances.

Non-Mapped Hazards

The remaining natural hazards (earthquake, winter storm, hailstorm, thunderstorm, windstorm, drought, wildfire, etc.) can be considered to have equal risk and impact throughout the county, therefore, an asset inventory was not conducted as all assets within the county would be considered at risk.

2. Loss Estimation

The final step in the risk assessment process is the loss estimation. This step helps to estimate the potential losses to the identified at-risk properties. In order to conduct the loss estimation each property was assigned a value based on data collected from the Jefferson County Tax Assessor. Parcel location information was determined using the E-911 data which was then cross referenced with the tax map to determine the tax ID number for each structure within the hazard area. This information, along with the deed record and the property owner, was used to obtain the assessed value. The assessed values are considered to be 60% of the market value as of June 2002.

Loss estimations were conducted only for the mapped hazards. Loss estimations were calculated and assessed values were obtained for each of the properties located within the identified flood, landslide, and land subsidence hazard areas. In the event that assessed values were unavailable for a particular property an average was applied based on the property use type (commercial or residential). Individual averages were developed for the county and the municipalities for flood, landslide, and land subsidence hazards. Properties classified as “other” for the purposes of this analysis are assumed to be tax-exempt structures without any available assessed value information. For each of the hazards described below loss estimations were based on an assumption of 100% loss as data was not available to make more accurate potential damage assessments.

Flood

According to the asset inventory there were 382 properties across the county that were located in the floodplain. Based on this analysis the flood loss estimation for all of Jefferson County is $53,978,648. The following table provides a breakdown of these estimates by municipality.

Table 9. Jefferson County Flood Loss Estimation

Type	Charles Town	Ranson	Harpers Ferry	Shepherdstown	Unincorporated County	Total
Commercial	$317,500