SOUTHSIDE HAMPTON ROADS HAZARD MITIGATION PLAN VULNERABILITY ASSESSMENT INTRODUCTION The Vulnerability Assessment section builds upon the information provided in the Hazard Identification and Analysis by identifying community assets and development trends in the region, then assessing the potential impact and amount of damage (loss of life and/or property) that could be caused by each hazard event addressed in this risk assessment. The primary objective of this level of vulnerability assessment is to prioritize hazards of concern to the region adding to the foundation for mitigation strategy and policy development. Consistent with the preceding sections, the following hazards are addressed in this assessment: FLOOD HURRICANES AND TROPICAL STORMS SEVERE THUNDERSTORMS LIGHTNING TORNADOES WINTER STORMS AND NOR EASTERS EROSION (COASTAL AND RIVERINE) EARTHQUAKES LANDSLIDES SINKHOLES DROUGHT WILDFIRE DAM/LEVEE FAILURE TSUNAMIS EXTREME TEMPERATURES To complete the vulnerability assessment, best available data was collected from a variety of sources, including local, state and federal agencies, and multiple analyses were applied through qualitative and quantitative means (further described below). Additional work will be done on an ongoing basis to enhance, expand and further improve the accuracy of the baseline results, and it is expected that this vulnerability assessment will continue to be refined through future plan updates as new data and loss estimation methods become available. The findings presented in this section with regard to vulnerability were developed using best available data, and the methods applied have resulted in an approximation of risk. These estimates should be used to understand relative hazard risk and the potential losses that may be incurred; however, uncertainties are inherent in any loss estimation methodology, arising in part from incomplete scientific knowledge concerning specific hazards and their effects on the built environment, as well as incomplete data sets and from approximations and simplifications that are necessary in order to provide a meaningful analysis. Further, most data sets used in this assessment contain relatively short periods of records which increases the uncertainty of any statistically-based analysis.
5:2 METHODOLOGIES USED Two distinct risk assessment methodologies were used in the formation of this vulnerability assessment. The first consists of a quantitative analysis that relies upon best available data and technology, while the second approach consists of a qualitative analysis that relies more on local knowledge and rational decision making. Upon completion, the methods are combined to create a hybrid approach for assessing hazard vulnerability for the region that allows for some degree of quality control and assurance. The methodologies are briefly described and introduced here and are further illustrated throughout this section. For each hazard addressed in this section, vulnerability is summarized in part by an annualized loss estimate specific to that hazard, along with a PRI value (described in detail below). QUANTITATIVE METHODOLOGY The quantitative assessment consists of utilizing Hazards U.S. Multi-Hazard (HAZUS-MH) software, a geographic information system (GIS)-based loss estimation tool available from the Federal Emergency Management Agency (FEMA), along with a statistical risk assessment methodology for hazards outside the scope of HAZUS-MH. For the flood hazard, the quantitative assessment incorporates a detailed GISbased approach using best available local data from the jurisdictions in the region. When combined, the results of these vulnerability studies are used to form an assessment of potential hazard losses (in dollars) along with the identification of specific community assets that are deemed potentially at-risk. Explanation of HAZUS-MH and Statistical Risk Assessment Methodology HAZUS-MH is FEMA s nationwide standardized loss estimation software package, built on an integrated GIS platform with a national inventory of baseline geographic data (including information on the region s general building stock and dollar exposure). Originally designed for the analysis of earthquake risks, FEMA has expanded the program to allow for the analysis of multiple hazards: namely the flood and wind (hurricane wind) hazards. By providing estimates on potential losses, HAZUS-MH facilitates quantitative comparisons between hazards and may assist in the prioritization of hazard mitigation activities. HAZUS-MH uses a statistical approach and mathematical modeling of risk to predict a hazard s frequency of occurrence and estimated impacts based on recorded or historic damage information. The HAZUS-MH risk assessment methodology is parametric, in that distinct hazard and inventory parameters such as wind speed and building type, for example were modeled using the HAZUS-MH software to determine the impact (damages and losses) on the built environment. Figure 5.1 shows a conceptual model of HAZUS-MH methodology. More information on HAZUS-MH loss estimation methodology is available through FEMA at www.fema.gov/hazus.
5:3 FIGURE 5.1: CONCEPTUAL MODEL OF HAZUS MH METHODOLOGY Sources: Federal Emergency Management Agency; PBS&J This risk assessment utilized HAZUS-MH to produce regional profiles and estimated losses for two of the hazards addressed in this section: hurricane winds and earthquakes. For each of these hazards, HAZUS-MH was used to generate probabilistic worst case scenario events to show the maximum potential extent of damages. It is understood that those events which could occur of less severe magnitude would likely result in fewer losses than those calculated here. Explanation of GIS-based (Non-HAZUS MH ) Risk Assessment Methodology For hazards outside the scope of HAZUS-MH, a specific statistical risk assessment methodology was designed and applied to generate potential loss estimates. The approach is based on the same principals as HAZUS-MH, but does not rely on readily available automated software. First, historical data is compiled for each hazard to relate occurrence patterns (frequency, intensity, damage, etc.) with existing hazard models. Statistical evaluations are then applied in combination with engineering modeling to develop damage functions that can generate annualized losses.
5:4 The use of the statistical risk assessment methodology provides a determination of estimated annualized loss 1 for the following hazards: Severe Thunderstorms Lightning Tornadoes Winter Storms and Nor easters Erosion Landslides Sinkholes Drought Wildfire Dam/Levee Failure Tsunamis Extreme Temperatures When possible, quantitative hazard loss estimates are compared with historical damage data as recorded through the National Weather Service/National Climatic Data Center and other reliable data sources. To determine annualized losses for the flood hazard (both riverine and surge), a detailed GIS analysis was conducted using local tax parcel data and maps of flood hazard areas to determine at-risk properties. This analysis was conducted independent of the HAZUS-MH program. The first step in conducting this analysis included the collection of relevant GIS data from local, state and national/federal sources. These sources include the various Town, City and County GIS Departments, federal agencies such as FEMA, the United States Geological Survey (USGS), and the National Oceanic and Atmospheric Administration (NOAA). Once all data was acquired, ESRI ArcGIS 9 was used to assess specific risks to people, public buildings and infrastructure utilizing digital hazard data in combination with the locally-available GIS data layers. Primary data layers include Census 2000 data, along with geo-referenced point locations for public buildings, critical facilities, hazardous materials sites and infrastructure elements. Using these data layers, risk was assessed and described by determining the parcels and/or point locations that intersected with the delineated flood hazard areas. 1 By annualizing estimated losses, the historic patterns of frequent smaller events are coupled with infrequent but larger events to provide a balanced presentation of the overall, long-term risk.
5:5 QUALITATIVE METHODOLOGY The qualitative assessment relies less on technology, but more on historical and anecdotal data, community input and professional judgment regarding expected hazard impacts. The qualitative assessment completed for the Southside Hampton Roads region is based on the Priority Risk Index (PRI), a tool used by PBS&J to measure the degree of risk for identified hazards in a particular planning area. The PRI is also used to assist community officials in ranking and prioritizing those hazards that pose the most significant threat to their area based on a variety of factors deemed important by the Mitigation Planning Committee and other stakeholders in the hazard mitigation planning process. While the quantitative assessment focuses on using best available data, computer models and GIS technology, the PRI system relies more on historical data, local knowledge and the general consensus of the Mitigation Planning Committee. The PRI is used for hazards with no available GIS data or relevant information to perform quantitative analyses, and also provides an important opportunity to compare, crosscheck or validate the results of those that do have available data. The PRI results in numerical values that allow identified hazards to be ranked against one another (the higher the PRI value, the greater the hazard risk). PRI values are obtained by assigning varying degrees of risk to five categories for each hazard (probability, impact, spatial extent, warning time and duration). Each degree of risk has been assigned a value (1 to 4) and an agreed upon weighting factor 2, as summarized in Table 5.1. To calculate the PRI value for a given hazard, the assigned risk value for each category is multiplied by the weighting factor. The sum of all five categories equals the final PRI value, as demonstrated in the example equation below: PRI VALUE = [(PROBABILITY x.30) + (IMPACT x.30) + (SPATIAL EXTENT x.20) + (WARNING TIME x.10) + (DURATION x.10)] According to the weighting scheme applied for the Southside Hampton Roads region, the highest possible PRI value is 4.0. Prior to being finalized, PRI values for each hazard were reviewed and accepted by the Mitigation Planning Committee. SUMMARY Using both the qualitative and quantitative analyses to evaluate the hazards that impact the region provides members of the Mitigation Planning Committee with a dual-faceted review of the hazards. This allows officials to not only recognize those hazards that may potentially be the most costly, but also to plan and prepare for those hazards that, although may not cause much monetary damage, could put a strain on the local resources needed to recover after their impact on the county. All conclusions of the vulnerability assessment completed for the region and participating jurisdictions are presented in Conclusions on Hazard Risk at the end of this section. Findings for each hazard are detailed in the hazard-by-hazard vulnerability assessment that follows, beginning with an overview of general asset inventory and exposure data for the Southside Hampton Roads region. 2 The Mitigation Planning Committee based upon any unique concerns for the planning area may also adjust the PRI weighting scheme.
5:6 TABLE 5.1: SUMMARY OF PRIORITY RISK INDEX (PRI) PRI CATEGORY Probability Impact Spatial Extent Warning Time Duration LEVEL DEGREE OF RISK CRITERIA INDEX VALUE Unlikely Less than 1% annual probability 1 Possible Between 1 and 10% annual probability 2 Likely Between 10 and 100% annual probability 3 Highly Likely 100% annual probability 4 Very few injuries, if any. Only minor property Minor damage and minimal disruption on quality of life. 1 Temporary shutdown of critical facilities. Minor injuries only. More than 10% of property in Limited affected area damaged or destroyed. Complete 2 shutdown of critical facilities for more than one day. Multiple deaths/injuries possible. More than 25% Critical of property in affected area damaged or destroyed. Complete shutdown of critical facilities for more 3 than one week. High number of deaths/injuries possible. More Catastrophic than 50% of property in affected area damaged or destroyed. Complete shutdown of critical facilities 4 for 30 days or more. Negligible Less than 1% of area affected 1 Small Between 1 and 10% of area affected 2 Moderate Between 10 and 50% of area affected 3 Large Between 50 and 100% of area affected 4 More than 24 hours Self explanatory 1 12 to 24 hours Self explanatory 2 6 to 12 hours Self explanatory 3 Less than 6 hours Self explanatory 4 Less than 6 hours Self explanatory 1 Less than 24 hours Self explanatory 2 Less than one week Self explanatory 3 More than one week Self explanatory 4 Source: Southside Hampton Roads Mitigation Planning Committee; PBS&J ASSIGNED WEIGHTING FACTOR 30% 30% 20% 10% 10%
5:7 OVERVIEW OF SOUTHSIDE HAMPTON ROADS VULNERABILITY DEMOGRAPHICS According to the U.S. Census Bureau, the total population of Southside Hampton Roads region in 2000 was 860,870. (For comparison, the total population in 2000 for the state of Virginia as a whole was 7,078,515) The average number of persons and housing units per square mile, according to the 2000 census, is 811 and 318 respectively. These numbers are significantly higher than the state average. The City of Virginia Beach contains the greatest population and housing units among cities and towns in the planning area. Table 5.2 provides a summary of population and demographic characteristics for the region. TABLE 5.2: POPULATION AND DEMOGRAPHIC CHARACTERISTICS JURISDICTION TOTAL POPULATION UNDER 18 YEARS OLD (%) 65 YEARS AND OVER (%) WHITE POPULATION (%) DISABILITY STATUS (%) Isle of Wight County 29,728 25 12.2 71.1 20.1 Norfolk 234,403 24 10.9 48.4 23.5 Portsmouth 100,565 26 13.8 45.8 24.7 Smithfield 6,324 27 13.6 67.2 22.1 Suffolk 63,677 28 11.4 53.8 24.4 Virginia Beach 425,257 27 8.4 71.4 15.3 Windsor 916 24 12.4 89.7 19.9 VIRGINIA 7,078,515 25 11.2 72.3 17.5 Source: U.S. Census Bureau (2000) Figure 5.2 shows the distribution of this population across the planning area based on the number of persons per census block. 3 3 It is important to note that with this type of GIS-based map the graduated coloring method used to show the number of persons living within each census block can in some instances be visually misleading at first glance, as highly populated areas may appear to be scarcely populated due to the fact that the population is divided into many small census blocks. The same can be true for large census blocks that show large numbers of persons but that cover more land area than the smaller census blocks.
5:8 GENERAL ASSET INVENTORY The total dollar exposure of buildings within the Southside Hampton Roads region is estimated to be approximately $66,439,169,000. This figure is based on an estimated 261,035 residential, commercial, industrial and other buildings located throughout the region, derived from HAZUS-MH data 4 (Table 5.3). The total dollar exposure accounts for both building value ($42,014,402,000) and contents value ($24,424,767,000). Taken together, the building and contents values provide an estimate of the aggregated total replacement value for the region s assets. Figures 5.3 through 5.5 illustrate geographically the concentration of commercial, industrial, and residential dollar exposure in the Southside Hampton Roads region based on HAZUS-MH data. TABLE 5.3: BUILDING INVENTORY IN SOUTHSIDE HAMPTON ROADS JURISDICTION NUMBER OF BUILDINGS RESIDENTIAL COMMERCIAL INDUSTRIAL OTHER TOTAL Isle of Wight County 11,707 73 3 10 11,793 Norfolk 57,859 920 117 250 59,146 Portsmouth 30,500 214 18 79 30,811 Suffolk 21,568 122 15 40 21,745 Virginia Beach 135,766 1,393 115 266 137,540 TOTAL 257,400 2,722 268 645 261,035 JURISDICTION BUILDING AND CONTENTS VALUES RESIDENTIAL COMMERCIAL INDUSTRIAL OTHER TOTAL Isle of Wight County $1,206,987,000 $102,689,000 $17,911,000 $23,701,000 $1,351,288,000 Norfolk $9,998,217,000 $1,663,410,000 $237,610,000 $226,515,000 $12,125,752,000 Portsmouth $4,211,183,000 $314,477,000 $49,765,000 $88,866,000 $4,664,291,000 Suffolk $2,480,542,000 $230,951,000 $39,958,000 $52,654,000 $2,804,105,000 Virginia Beach $18,256,280,000 $2,170,665,000 $271,859,000 $370,162,000 $21,068,966,000 Total Building Value $36,153,209,000 $4,482,192,000 $617,103,000 $761,898,000 $42,014,402,000 Total Content Value $18,087,270,000 $4,734,868,000 $794,635,000 $807,994,000 $24,424,767,000 GRAND TOTAL $54,240,479,000 $9,217,060,000 $1,411,738,000 $1,569,892,000 $66,439,169,000 Source: HAZUS-MH CRITICAL FACILITIES There is no comprehensive database of critical facilities and infrastructure for the Southside Hampton Roads region. Moreover, there is no universally accepted definition of what constitutes critical facilities and infrastructure nor is one associated with FEMA and DMA 2000 planning requirements. However, for purposes of this Plan, critical facilities and infrastructure are identified as those facilities or systems whose incapacity or destruction would present an immediate threat to life, public health, and safety or have a debilitating effect on the economic security of the region. 5 This includes the following facilities and systems based on their high relative importance for the delivery of vital services, the protection of special populations, and other important functions in the Southside Hampton Roads region: 4 HAZUS-MH uses Census 2000 and Dunn and Bradstreet (2002) data for its default inventories. Any values unavailable in the current version of the HAZUS-MH software are not reflected. 5 It should be noted that Dominion Power (the region s electric power provides) maintains a listing of critical facilities for the participating jurisdictions in the Southside Hampton Roads region. This listing is separate from the one included in this Plan.
5:9 Emergency Operations Centers (EOCs) Hospitals and medical care facilities Police stations Fire stations Schools (particularly those designated as shelters) Hazardous materials facilities Potable water facilities Wastewater facilities Energy facilities (electric, oil and natural gas) Communication facilities In preparing the inventory of critical facilities for the Southside Hampton Roads region, each participating jurisdiction was asked to submit best available GIS data layers for their primary critical facilities to be used in combination with HAZUS-MH inventory data 6. This resulted in the identification of hundreds of critical facilities for the region. It is understood that this listing is incomplete due to data limitations associated with both the local GIS and HAZUS-MH inventories, but that further enhancements to the data will be made over time and incorporated during future plan updates. Because of the sensitive nature of critical facility information, this listing has been made an appendix of this plan (Appendix B). The data was acquired from the HAZUS-MH database of critical facilities for each jurisdiction and verified by local jurisdiction officials for accuracy. Figures AB1 through AB-5 (located in Appendix B) show the general location of critical facilities in each jurisdiction. Table 5.4 shows the results of a general analysis of the critical facilities that are located in the high wildfire risk area, 100-year floodplain, Flood Zone VE and the Storm Surge Zone for a Category 3 hurricane. The critical facility data-points from the HAZUS-MH software were used for this analysis except where better local GIS data was available. In those cases, the GIS data points from the local GIS departments were used instead of the HAZUS-MH data. TABLE 5.4: CRITICAL FACILITIES LOCATED IN HAZARD AREAS Jurisdiction Facility Type High Wildfire Risk 100-year Floodplain Flood Zone VE Storm Surge Category 3 Isle of Wight County Fire/Rescue Station 1 1 0 1 Police Facility 0 0 0 0 Water Plants 0 2 0 2 Norfolk Fire/Rescue Station 0 2 0 13 School 0 2 0 88 Water Plants 0 0 0 3 Wastewater Facilities 0 0 0 3 Police Facility 0 0 0 5 Medical Facilities 0 0 0 7 Portsmouth Wastewater Facilities 0 1 0 1 Schools 0 4 0 13 Police Facility 0 1 0 3 Fire/Rescue Station 0 1 0 3 6 For purposes of this assessment, local GIS data submitted by participating jurisdictions was considered best available data (over HAZUS-MH inventory data). If no local GIS data was submitted, then HAZUS-MH inventory data was considered best available data.
5:10 TABLE 5.4: CRITICAL FACILITIES LOCATED IN HAZARD AREAS Jurisdiction Facility Type High Wildfire Risk 100-year Floodplain Flood Zone VE Storm Surge Category 3 Suffolk Water Plants 0 0 0 1 Schools 0 1 0 0 Smithfield None 0 0 0 0 Windsor None 0 0 0 0 Virginia Beach Fire/Rescue Station 0 3 0 4 ZONING AND LAND USE Police Facility 0 0 0 9 Water Plants 0 0 0 2 Wastewater Facilities 0 0 1 2 Schools 0 8 0 64 Medical Facilities 0 0 0 1 In order to regulate current and future land use and guide overall development patterns, all of the jurisdictions in the Southside Hampton Roads region have adopted a zoning ordinance that enforces standards for designated zoning districts. Zoning maps are useful planning tools, demonstrating the type and location of projected community development. Because of the number of jurisdictions participating in this Plan, and the many differences in zoning designations across the region, it is not feasible to show a regional map of the various zoning districts across the region. However, each jurisdiction should compare their zoning, land use maps and future land use maps with the known hazard area maps to determine if future development is being encouraged in these hazardous zones. MANUFACTURED HOUSING AND THE AGE OF BUILDINGS The vulnerability of manufactured homes versus those built on-site can vary due to several factors. These include the age of construction, the materials and construction techniques used, the adherence to past and current building codes, and the method of installation. In the case of manufactured housing, their proper installation can significantly affect vulnerability. For instance, with regard to wind-related hazards such as tropical cyclones, severe thunderstorms and tornadoes, estimates based on regional trends show that 50 percent of manufactured homes built prior to 1976 (pre-hud structures) are not secured with tie downs. Of the manufactured homes built between 1976 and 1993, 25 percent have no tie downs. Of those built from 1994 to 2004, 1 percent have no tie downs. These statistics demonstrate that older manufactured homes specifically those with no tie downs are at greater risk from high wind hazards (Blue Sky Foundation of North Carolina). A similar logic applies to the age of buildings and flood hazard vulnerability. As shown in Table 5.5, the communities in the Southside Hampton Roads region joined the National Flood Insurance Program (NFIP) either in the early 1970 s or early 1990 s. In order to join the NFIP, each participating jurisdiction is required to adopt and enforce its own floodplain management ordinance. As a result, structures built after joining the NFIP are assumed to be less vulnerable to future flood hazards than pre-firm construction, assuming other environmental conditions remain constant. It is important to note, however, that continued development, for example, can cause a significant rise in flood elevations.
5:11 TABLE 5.5: NFIP ENTRY DATE AND CURRENT EFFECTIVE FIRM JURISDICTION NFIP ENTRY DATE CURRENT EFFECTIVE FIRM Isle of Wight County 8/19/1991 9/4/2002 Norfolk 8/1/1979 7/16/1996 Portsmouth 7/2/1971 11/2/1983 Smithfield 12/5/1990 9/4/2002 Suffolk 11/16/1990 9/4/2002 Virginia Beach 4/23/1971 12/5/1996 Windsor 8/1/1990 9/4/2002 Source: Federal Emergency Management Agency DEVELOPMENT TRENDS Two factors that contribute to an overall understanding of development trends are population change and economic growth. According to the U.S. Census Bureau, the average rate of population growth in the Southside Hampton Roads region 1990 and 2000 was 7.1 percent. This rate is slower than the state average of 14.4 percent. Suffolk experienced the greatest population growth rate with a 22.1 percent increase followed by Isle of Wight County with 18.7 and Virginia Beach with an 8.2 percent increase. Norfolk experienced a loss in population with a -10.3 percent growth rate from 1990 to 2000, as did Portsmouth with a -3.2 percent growth rate. There is an interesting dynamic taking place in the region as populations increase for some of the jurisdictions and decrease for others. As discussed in Section 3, these trends are expected to continue. In the areas of population increase, new housing construction will also increase which creates jobs and increases the inflow of dollars to the local economy. Local employment and retail sales for these communities continue to look positive for the immediate future. However, in the areas of population decline, unemployment and loss of businesses could continue to negatively impact the area in terms of economic growth. AGRICULTURAL VULNERABILITY While most of the Southside Hampton Roads region is urbanized or developed, much of Isle of Wight County, Suffolk and portions of Virginia Beach remain undeveloped and used for agricultural purposes. As discussed in the Community Profile section of this Plan, row crops constitute 13.7% of the total land use in the Southside Hampton Roads region (Isle of Wight County 25.3%, Suffolk, 22.9% and Virginia Beach 17.1%). The following crops are grown in Isle of Wight County, Suffolk and Virginia Beach: Corn Cotton Peanuts Soybeans Tall Fescue Wheat Areas where agriculture is the primary land use are typically more vulnerable to the drought hazard because of the dependency of agriculture on water. These areas can also experience losses that are difficult to capture for other hazards such as flooding and hurricanes.
5:12 FLOOD FLOOD (100-YEAR) PRI Value: 3.5 Annualized Loss Estimate: $48,172,702 FLOOD (STORM SURGE) PRI Value: 2.7 Annualized Loss Estimate: $206,624,689 The vulnerability assessment for the flood hazard includes the findings of the qualitative assessment conducted, an overview of National Flood Insurance Program (NFIP) statistics, repetitive loss properties (as defined and identified by the NFIP), estimates of potential losses, and future vulnerability and land use. As described in detail in the Hazard Identification and Analysis section, the National Climatic Data Center only has records for 21 significant flood events in just the past 10 years for the Southside Hampton Roads region, amounting to approximately $670,000 in reported property damage. Also discussed in the Hazard Identification and Analysis are historic storms such as Hurricanes Isabel, Floyd and the 1933 hurricane that each caused flooding in the region. Historically, the region is vulnerable to the flood hazard and floods events occur on a fairly frequent basis. According to the qualitative assessment performed using the PRI tool, the flood hazard scored a PRI value of 3.5 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.6 summarizes the risk levels assigned to each PRI category. TABLE 5.6: QUALITATIVE ASSESSMENT FOR FLOOD (100-YEAR) PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Highly Likely Catastrophic Moderate More Than 24 Hours More Than 1 Week Source: Southside Hampton Roads Mitigation Planning Committee The storm surge hazard was analyzed separately from the 100-year riverine / coastal flood hazard, and scored a PRI value of 2.7 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.7 summarizes the risk levels assigned to each PRI category. TABLE 5.7: QUALITATIVE ASSESSMENT FOR FLOOD (STORM SURGE) PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Possible Catastrophic Moderate More than 24 Hours Less than 24 Hours Source: Southside Hampton Roads Mitigation Planning Committee NFIP STATISTICS AND REPETITIVE LOSS PROPERTIES Regionwide there are currently 32,766 flood insurance policies in place, providing a total amount of $5,793,863,900 in coverage. Table 5.8 provides details for each jurisdiction with regard to the community s date of entry into the National Flood Insurance Program (NFIP), date of the community s current effective Flood Insurance Rate Map (FIRM), average number of losses, number of repetitive loss properties, total losses, total dollar amount of payments and average payment per loss.
5:13 Reducing the number of repetitive loss properties insured by the NFIP is a nationwide emphasis of the Federal Emergency Management Agency. A total of 502 repetitive loss properties as defined by the NFIP 7 are known to exist within the Southside Hampton Roads region. These 502 properties have experienced a total of 1,240 individual insured losses. TABLE 5.8: NFIP STATISTICS AND REPETITIVE LOSS PROPERTIES JURISDICTION NFIP ENTRY DATE CURRENT EFFECTIVE FIRM AVERAGE NUMBER OF LOSSES NUMBER OF REPETITIVE LOSS PROPERTIES TOTAL LOSSES TOTAL PAYMENTS AVERAGE PAYMENT PER LOSS Isle of Wight County 8/19/1991 9/4/2002 2.0 6 12 $476,483 $238,241 Norfolk 8/1/1979 7/16/1996 2.3 180 420 $5,056,529 $2,137,576 Portsmouth 7/2/1971 11/2/1983 2.3 43 101 $1,001,498 $438,799 Smithfield 12/5/1990 9/4/2002 2.8 4 11 $291,108 $121,063 Virginia Beach 4/23/1971 12/5/1996 2.6 260 676 $8,051,288 $2,929,339 Windsor 8/1/1990 9/4/2002 N/A N/A N/A N/A N/A TOTAL 2.0 493 1220 $14,876,906 $977,503 Sources: National Flood Insurance Program (as of 12/31/2003) 7 Under the NFIP, FEMA defines a repetitive loss property as any NFIP-insured property that, since 1978 and regardless of any change(s) of ownership during that period, has experienced: a) four or more paid flood losses; or b) two paid flood losses within a 10-year period that equal or exceed the current value of the insured property; or c) three or more paid losses that equal or exceed the current value of the insured property.
5:14 ESTIMATES OF POTENTIAL LOSSES Following a detailed analysis of the study area using best available GIS data including the existing 100- year floodplain, 35,482 properties were determined to be flood-prone amounting to a total net present worth of approximately $11,032,679,686 billion in exposure. Table 5.9 provides a detailed listing of the number of structures, number of structures determined to be pre-firm 8 based on year built, and the assessed value of structures within the existing 100-year floodplain. An annualized loss estimate of $48,172,702 was determined using best available local property tax data, and assuming the 100-year flood event occurs once every 100 years. TABLE 5.9: OVERVIEW OF POTENTIALLY AT-RISK PROPERTIES FOR FLOOD (100-YEAR) JURISDICTION NUMBER OF STRUCTURES EXISTING 100-YEAR FLOODPLAIN NUMBER OF PRE- ASSESSED VALUE FIRM STRUCTURES VALUE OF PRE-FIRM STRUCTURES Isle of Wight County 374 $124,445,000 Unknown 9 Unknown Norfolk 14,037 $3,014,779,700 11,207 $2,791,581,500 Portsmouth 8,292 $4,541,637,210 Unknown Unknown Smithfield 51 $16,258,300 Unknown Unknown Suffolk 1,612 $206,889,500 595 $70,567,300 Virginia Beach 11,114 $3,128,490,076 4,182 $1,152,243,064 Windsor 2 $179,900 Unknown Unknown TOTAL 35,482 $11,032,679,686 15,984 $4,014,391,864 Sources: Federal Emergency Management Agency (Q3 flood data); Local GIS data 8 Pre-FIRM indicates that the structure was built prior to the local enforcement of NFIP standards and is therefore considered to be at potentially greater risk from the flood hazard. 9 In jurisdictions where the year-built date of structures was not provided, Number and Value of Pre-FIRM Structures has been marked as Unknown.
5:15 Following a detailed analysis of the study area using best available GIS data including SLOSH model data 10, 156,042 properties were determined to be at risk to storm surge from a Category 3 hurricane amounting to a total net present worth of approximately $25,828,086,183 billion in exposure. Table 5.10 provides a detailed listing of the estimated number of parcels, number of developed parcels, number of structures and assessed values of structures at risk to surge from a Category 3 event. An annualized loss estimate of $206,624,689 was determined using best available local property tax data, and assuming that the worst case scenario storm surge event for a Category 3 hurricane occurs once every 150 years. TABLE 5.10: OVERVIEW OF POTENTIALLY AT-RISK PROPERTIES FLOOD (STORM SURGE) JURISDICTION NUMBER OF PARCELS CATEGORY 3 STORM SURGE INUNDATION ZONE DEVELOPED PARCELS NUMBER OF STRUCTURES VALUE OF STRUCTURES Isle of Wight County 2,437 591 653 $54,221,100 Norfolk 115,535 91,358 85,754 $16,293,288,040 Portsmouth 35,343 22,733 49,102 $1,240,970,150 Smithfield 793 91 94 $21,886,200 Suffolk 3,723 1,481 2,069 $313,003,000 Virginia Beach 42,941 39,788 74,373 $7,904,717,693 Windsor 0 0 0 $0 TOTAL 200,772 156,042 212,045 $25,828,086,183 Sources: Southside Hampton Roads Planning District Commission / National Weather Service (SLOSH data); Local GIS data FUTURE VULNERABILITY AND LAND USE For both the riverine and storm surge flooding hazards, future vulnerability will be determined, in part, by local officials. Flood hazard and SLOSH maps have been developed to indicate what areas of the jurisdictions are most vulnerable to these hazards. While these maps are often outdated, efforts are being made across the region to improve or update many of these maps. It is the responsibility of the local officials to enforce local floodplain regulations, flood damage prevention ordinances or other forms of development policies that either limit or restrict development to varying degrees in these hazard areas. 10 The SLOSH model is described in Section 4: Hazard Identification and Analysis.
5:16 HURRICANES AND TROPICAL STORMS PRI Value: 3.2 Annualized Loss Estimate: $33,546,000 Historical evidence shows that the Southside Hampton Roads region is vulnerable to damaging hurricane and tropical storm-force winds. 11 As discussed in detail in the Hazard Identification and Analysis section, 106 hurricanes and tropical storms have passed within 75 miles of the region since 1851, 29 of which crossed directly through the region. This translates into an estimate of a 68% chance that a storm may potentially impact the region on an annual basis. According to the qualitative assessment performed using the PRI tool, the hurricane and tropical storm hazard scored a PRI value of 3.20 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.11 summarizes the risk levels assigned to each PRI category. TABLE 5.11: QUALITATIVE ASSESSMENT FOR HURRICANES AND TROPICAL STORMS PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Likely Catastrophic Large More than 24 Hours Less than 24 Hours Source: Southside Hampton Roads Mitigation Planning Committee ESTIMATES OF POTENTIAL LOSSES Detailed loss estimates for the hurricane and tropical storm hazard (as these hazards relate to wind) were developed based on probabilistic scenarios using HAZUS-MH (Level 1 analysis). 12 Table 5.12 shows estimates of potential building damage for the 100- and 500-year return periods, as well as annualized losses, by building occupancy type. In summary, Southside Hampton Roads region may be susceptible to an estimated total of approximately $664 million in building damages from a 100-year wind event, increasing to up to $3.6 billion for a 500-year event. Annualized losses are estimated to be approximately $33 million. These figures are based on worst-case scenarios. TABLE 5.12: ESTIMATES OF POTENTIAL BUILDING DAMAGE BUILDING OCCUPANCY TYPE 100-YEAR EVENT 500-YEAR EVENT ANNUALIZED Isle of Wight County $2,668,000 $104,213,000 $1,258,000 Norfolk $454,774,000 $2,532,914,000 $21,510,000 Portsmouth $174,718,000 $732,457,000 $7,736,000 Suffolk $32,010,000 $210,317,000 $3,042,000 Virginia Beach $881,106,000 $5,667,053,000 $46,592,000 TOTAL $664,170,000 $3,579,901,000 $33,546,000 Source: HAZUS-MH HAZUS-MH was also used to produce building damage estimates based on percentage of damage (by damage state) for the 100- and 500-year return periods (Table 5.13). In summary, for the 100-year event 11.4 percent of the total building area might potentially suffer minor damage with 0.3 percent buildings 11 Refer to the Hazard Identification and Analysis section of this risk assessment for detailed historical information. 12 According to FEMA s HAZUS Web site, a Level 1 analysis yields a rough estimate based on the nationwide database and is a great way to begin the risk assessment process and prioritize high-risk communities.
5:17 being completely destroyed. For the 500-year event, 15.2 percent of the total building area might potentially suffer minor damage with 3.3 percent being completely destroyed. TABLE 5.13: ESTIMATES OF POTENTIAL BUILDING DAMAGE BY DAMAGE STATE 13 BUILDING OCCUPANCY TYPE TOTAL SQUARE FEET MINOR (%) MODERATE (%) SEVERE (%) DESTRUCTION (%) 100-YR 500-YR 100-YR 500-YR 100-YR 500-YR 100-YR 500-YR Isle of Wight County 11,793 1.0 29.8 0.0 12.0 0.0 2.7 0.0 2.5 Norfolk 59,146 30.2 30.9 10.8 31.0 1.1 13.0 0.8 9.9 Portsmouth 30,811 29.3 35.8 9.3 24.5 1.0 8.2 0.7 6.2 Suffolk 21,745 12.5 31.3 1.8 12.6 0.1 3.1 0.1 2.8 Virginia Beach 137,540 30.3 30.0 9.4 27.9 1.2 14.5 1.0 13.5 TOTAL 261,035 11.4 15.2 3.7 11.5 0.4 4.3 0.3 3.3 Source: HAZUS-MH FUTURE VULNERABILITY AND LAND USE All future structures built in the Southside Hampton Roads region will likely be exposed to hurricane and tropical storm-force winds and may also experience damage not accounted for in the loss estimates presented in this section. However, continued enforcement of building codes, flood damage prevention ordinances and other local regulatory tools and policies is expected to minimize future losses as construction and planning continue to seek higher standards. 13 For detailed definitions of the four damage states, please refer to the HAZUS-MH User Manual for the Hurricane Model.
5:18 SEVERE THUNDERSTORMS PRI Value: 2.8 Annualized Loss Estimate: $387,961 Historical evidence shows that Southside Hampton Roads region is vulnerable to severe thunderstorm activity, including related hazardous elements such as lightning and hail that often accompany these severe weather events. According to the qualitative assessment performed using the PRI tool, the severe thunderstorm hazard scored a PRI value of 2.8 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.14 summarizes the risk levels assigned to each PRI category. TABLE 5.14: QUALITATIVE ASSESSMENT FOR SEVERE THUNDERSTORMS PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Highly Likely Minor Large Less than 6 Hours Less than 6 Hours Source: Southside Hampton Roads Mitigation Planning Committee ESTIMATES OF POTENTIAL LOSSES Because it cannot be predicted where severe thunderstorms may occur, it is not possible to map geographic boundaries for this hazard or produce detailed loss estimates. Therefore, the total dollar exposure figure of $66,439,169,000 for all buildings and contents within the planning area is considered to be exposed and could potentially be impacted on some level by this hazard. Based on historic property damages for the past 55 years (1950 to 2004), an annualized loss estimate of $387,961 was generated for severe thunderstorm damages combined with an annual probability of 563.6 percent in the planning area. These annualized loss and probability are presented in Table 5.15 by jurisdiction. TABLE 5.15: ESTIMATED ANNUALIZED LOSSES JURISDICTION ANNUALIZED LOSSES ANNUAL PROBABILITY Isle of Wight County $2,295 63.6% Norfolk $251,306 100.0% Portsmouth $1,318 56.4% Smithfield $2,357 14.5% Suffolk $4,626 109.1% Virginia Beach $125,817 207.3% Windsor $242 12.7% TOTAL $387,961 563.6% Source: Statistical Risk Assessment Methodology FUTURE VULNERABILITY AND LAND USE All future structures built in the Southside Hampton Roads region will likely be exposed to severe thunderstorms and may experience damage not accounted for in the estimated losses presented in this section. Based on projections of population growth in the Southside Hampton Roads region, the planning area may experience an estimated $426,757 in annualized losses by 2030.
5:19 LIGHTNING PRI Value: 2.7 Annualized Loss Estimate: Negligible Historical evidence shows that the Southside Hampton Roads region is vulnerable to lightning activity, which is often associated with severe thunderstorms that impact the region. According to the qualitative assessment performed using the PRI tool, the lightning hazard scored a PRI value of 2.7 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.16 summarizes the risk levels assigned to each PRI category. TABLE 5.16: QUALITATIVE ASSESSMENT FOR LIGHTNING PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Highly Likely Limited Small Less than 6 Hours Less than 6 Hours Source: Southside Hampton Roads region Planning Committee ESTIMATES OF POTENTIAL LOSSES Because it cannot be predicted where lightning may strike, it is not possible to map geographic boundaries for this hazard or produce detailed loss estimates. Therefore, the total dollar exposure figure of $66,439,169,000 for all buildings and contents within Southside Hampton Roads region is considered to be exposed and could potentially be impacted on some level by the lightning hazard. FUTURE VULNERABILITY AND LAND USE Because of the random nature of occurrence of the lightning hazard, it is difficult to assess future vulnerability and land use with regard to this particular hazard. In general, all buildings built in the future in this region and all future populations will be exposed and therefore at risk to the lightning hazard.
5:20 TORNADOES PRI Value: 3.0 Annualized Loss Estimate: $309,725 Historical evidence shows that the Southside Hampton Roads region is vulnerable to tornado activity, which often is associated with other severe weather events such as thunderstorm or tropical cyclone activity. According to the qualitative assessment performed using the PRI tool, the tornado hazard scored a PRI value of 3.0 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.17 summarizes the risk levels assigned to each PRI category. TABLE 5.17: QUALITATIVE ASSESSMENT FOR TORNADOES PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Highly Likely Critical Small Less than 6 Hours Less than 6 Hours Source: Southside Hampton Roads region Planning Committee ESTIMATES OF POTENTIAL LOSSES Because it cannot be predicted where a tornado may strike, it is not possible to map geographic boundaries for this hazard or produce detailed loss estimates. Therefore, the total dollar exposure figure of $66,439,169,000 for all buildings and contents within Southside Hampton Roads region is considered to be exposed and could potentially be impacted on some level by the tornado hazard. Based on historic property damages for the past 55 years (1950 to 2004), an annualized loss estimate of $309,725 and annual probability of 89.1 percent were generated for the tornado hazard. These annualized loss and probability are presented in Table 5.18 by jurisdiction. TABLE 5.18: ESTIMATED ANNUALIZED LOSSES MAGNITUDE OF EVENT ANNUALIZED LOSSES ANNUAL PROBABILITY Isle of Wight County $11,786 9.1% Norfolk $96,921 29.1% Portsmouth $167,236 3.6% Smithfield $641 3.6% Suffolk $17,875 21.8% Virginia Beach $15,266 21.8% Windsor N/A N/A TOTAL $309,725 89.1% Source: Statistical Risk Assessment Methodology FUTURE VULNERABILITY AND LAND USE All future structures built in Southside Hampton Roads region are likely to be exposed to the tornado hazard and may experience damage not accounted for in the estimated losses presented in this section. Based on projections of population growth in the Southside Hampton Roads region, the planning area may experience an estimated $340,698 in annualized losses by 2030.
5:21 WINTER STORMS PRI Value: 3.0 Annualized Loss Estimate: $1,416,633 Historical evidence shows that Southside Hampton Roads region is vulnerable to winter storm activity, including heavy snow, ice, extreme cold, freezing rain, and sleet. According to the qualitative assessment performed using the PRI tool, the winter storm hazard scored a PRI value of 3.0 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.19 summarizes the risk levels assigned to each PRI category. TABLE 5.19: QUALITATIVE ASSESSMENT FOR WINTER STORMS PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Likely Critical Large More than 24 Hours Less than 1 Week Source: Southside Hampton Roads Mitigation Planning Committee ESTIMATES OF POTENTIAL LOSSES Because winter storms typically affect large areas beyond county and municipal boundaries, it is not possible to map geographic locations within the region at specific risk from this hazard or produce detailed loss estimates. Therefore, the total dollar exposure figure of $66,439,169,000 for all buildings and contents within the Southside Hampton Roads region is considered to be exposed and could potentially be impacted on some level by the winter storm hazard. Based on historic property damages for the past twelve years (June 1993 to May 2005), an annualized loss estimate of $1,416,633 was generated for the winter storm hazard. This annualized loss is presented in Table 5.20 along with annual probability. It should be understood that with the winter storm hazard, potential losses may be inflated by additional, difficult to calculate factors such as the costs associated with the removal of snow from roadways, debris clean-up, indirect losses from power outages, etc. Because winter weather impacts the region uniformly, no winter storm vulnerability maps have been created. For maps of critical facilities and infrastructure that could potentially be impacted, see Appendix AB. TABLE 5.20: ESTIMATED ANNUALIZED LOSSES ANNUAL PROBABILITY ANNUALIZED LOSSES Source: Statistical Risk Assessment Methodology 2.0 $1,416,633 FUTURE VULNERABILITY AND LAND USE All future structures built in Southside Hampton Roads region are likely to be exposed to the winter storm hazard and may experience damage not accounted for in the estimated losses presented in this section.
5:22 Based on projections of population growth in the Southside Hampton Roads region, the jurisdictions may experience an estimated $1,558,296 in annualized losses by 2030.
5:23 EROSION (COASTAL AND RIVERINE) PRI Value: 2.1 Annualized Loss Estimate: Undetermined As documented in the Hazard Identification and Analysis section, the Southside Hampton Roads region is vulnerable to the long term effects of both riverine and coastal erosion. While riverine erosion presents a limited to moderate risk to property, coastal erosion remains a significant hazard of concern that must continue to be addressed through sustained shoreline management practices. To date, existing strategies for shoreline hardening and the implementation of numerous renourishment projects have been successful in eliminating major coastal erosion losses 14. According to the qualitative assessment performed using the PRI tool, the erosion hazard scored a PRI value of 2.1 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.21 summarizes the risk levels assigned to each PRI category. TABLE 5.21: QUALITATIVE ASSESSMENT FOR EROSION PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Likely Minor Small More than 24 Hours More than 1 Week Source: Southside Hampton Roads Mitigation Planning Committee ESTIMATES OF POTENTIAL LOSS It is difficult to determine the amount of property or the number of structures that are vulnerable to the erosion hazard. The jurisdictions in the region have demonstrated, through past projects such as the Virginia Beach Erosion Control and Hurricane Protection Project, that they are willing to take on projects to protect the coastal residences and commercial buildings located along the beach. Riverine erosion is a highly localized hazard concern and without accurate riverine erosion hazard maps, it is difficult to determine the number and value of properties at risk. FUTURE VULNERABILITY AND LAND USE It is difficult to assess future vulnerability and land use in regard to this hazard. Generally speaking, future vulnerability is going to depend greatly on appropriate local site planning and permitting where applicable. The jurisdictions in the region and the associated federal assistance will also need to continue to support the beach renourishment practices in order to avoid coastal erosion losses in the future. 14 The Norfolk District of the Army Corps of Engineers estimates that $82 million in damages were prevented during Hurricane Isabel in 2003 through the Virginia Beach Erosion Control and Hurricane Protection Project. This includes $52 million in damages to residential property, $15 million to commercial interests and $15 million to infrastructure.
5:24 EARTHQUAKES PRI Value: 1.9 Annualized Loss Estimate: $1,775,000 The annual probability of an earthquake event impacting the study area is estimated at 5 percent based on historical data. While the probability of an earthquake occurrence is relatively low, moderate losses should a significant earthquake event occur are possible. According to the qualitative assessment performed using the PRI tool, the earthquake hazard scored a PRI value of 1.9 (from a scale of 0 to 4, with 4 being the highest risk level). Table 5.22 summarizes the risk levels assigned to each PRI category. TABLE 5.22: QUALITATIVE ASSESSMENT FOR EARTHQUAKES PROBABILITY IMPACT SPATIAL EXTENT WARNING TIME DURATION Unlikely Minor Large Less than 6 Hours Less than 6 Hours Source: Southside Hampton Roads Mitigation Planning Committee ESTIMATES OF POTENTIAL LOSSES Table 5.23 provides generalized building damage estimates by jurisdiction for the 100-, 500- and 1,000- year return periods as well as annualized losses based on probabilistic scenarios using HAZUS-MH. The annualized building damage estimate for the earthquake hazard is $93,000, and in that estimate residential properties suffer more than 98 percent of the total damage. TABLE 5.23: ESTIMATES OF POTENTIAL BUILDING DAMAGE BUILDING OCCUPANCY TYPE 100-YEAR EVENT 500-YEAR EVENT 1,000-YEAR EVENT ANNUALIZED Isle of Wight County Negligible 15 $408,000 $1,092,000 $5,000 Norfolk Negligible $2,785,000 $7,422,000 $28,000 Portsmouth Negligible $1,358,000 $2,851,000 $11,000 Suffolk Negligible $833,000 $2,104,000 $8,000 Virginia Beach Negligible $4,468,000 $11,911,000 $41,000 TOTAL Negligible $9,852,000 $25,380,000 $93,000 Source: HAZUS-MH HAZUS-MH was also used to produce building damage estimates based on percentage of damage (by damage state) for the 500-, and 1,000-year return periods (Table 5.24). According to the HAZUS-MH model assumptions, there should be no building damage from 100-year earthquake event. 15 Damage less than $1,000