Pinellas County Community Ratings System. CRS Floodplain Management Plan

Transcription

1 Preface Pinellas County Community Ratings System Floodplain Management Plan Prepared by the Pinellas County Planning Department Under the Direction of the Community Ratings System Floodplain Management Committee For Adoption by the Pinellas County Board of County Commissioners September 1998 i

2 Preface PREFACE Organizing to Prepare the Plan Step 1: The Pinellas County Community Ratings System Floodplain Management Plan (CRS Plan) was prepared by the Pinellas County Planning Department under the direction of Brian Smith, AICP. Step 2: The planning process was conducted through a committee composed of staff from those departments of Pinellas County Government that will be implementing the recommendations within the CRS Plan. The following persons and/or their representatives participated in the planning process as members of the ning Committee: Name Brian K. Smith, Chairman Alternate: Gordon Beardslee Paul Cassel Alternate: John Cueva Robert A. Pensa Alternate: Dave Livesay David R. Bilodeau Alternate: Gary Vickers William M. Davis Alternate: None Ronnie J. Goodstein Alternate: Lennard Ciecieznski James Richter Alternate: George Owen Department Planning Development Review Services Building Emergency Management Environmental Management Public Affairs Public Works The CRS Committee conducted the planning process through a series of four meetings. These meetings were held in the main conference room of the Planning Department. The dates and discussion items presented at these meetings are provided on the following page. ii

3 Preface Date March 26, 1998 May 14, 1998 June 11, 1998 Discussion Items Introduction to the CRS Planning Process Assessing the Flood Hazard and Problems which Promote Flooding Setting Goals for the CRS Plan, Reviewing Possible Activities, Approval of Action Plan Public Involvement Step 1: Three public workshops were held, each in different areas of Pinellas County, at the end of the planning process to obtain public input on the draft CRS Plan before submittal to the BOCC. To inform the public about these workshops, a press release was issued and a mailout was conducted by the Department of Public Affairs. Mailouts were sent to homeowners associations and interested citizens throughout unincorporated Pinellas County. The meeting dates and locations were as follows: Abilities Inc., FL - High Point July 20, :00 PM Palm Harbor Public Library Seminole Community Library July 22, :00 PM July 27, :30 PM Step 2 (CRS Action #3): On June 13, 1998 the Pinellas County Planning Department set up a display at the 1998 Hurricane Expo explaining the CRS program and its planning process to Pinellas County residents. At the Expo, the Department also distributed helpful information concerning flood damage mitigation practices and the retrofitting of commercial and residential structures. Step 3 (CRS Action #5): To further promote flood hazard awareness, the Planning and Public Affairs Departments produce flyers which contain helpful information concerning flood hazard mitigation practices and the County s planning efforts. These flyers are distributed annually at the onset of hurricane season via enclosure with utility bills to all residents of unincorporated Pinellas County. In addition, the County also contacts homeowners associations of subdivisions and condominiums which are partially or entirely within the 100-year floodplain via letter and provides them with helpful flood hazard mitigation information. Both the utility flyers and homeowners association notices also provide information on contact personnel if further information is needed. iii

4 Preface Coordination with Other Agencies Step 1: In order ensure the consistency of the CRS Plan with those plans, procedures, programs and regulations of those agencies that implement floodplain management activities within Pinellas County, the Planning Department transmitted a letter to four agencies at the beginning of the planning process to solicit their input. This letter was transmitted on March 27, 1998 to the following personnel: Ms. Trisha Neasman Government Planning Coordinator Southwest Florida Water Management District 2379 Broad Street Brooksville, FL Mr. Charles Speights Director Department of Community Affairs Bureau of Recovery and Mitigation 2555 Shumard Oak Drive Tallahassee, FL Ms. Julia Greene Executive Director Tampa Bay Regional Council 9455 Koger Boulevard Suite 219 St. Petersburg, FL Mr. Ken Hutchinson Director Federal Emergency Management Agency Region IV 3003 Chamblee-Tucker Road Atlanta, GA Step 2: The aforementioned letters also requested these agencies to participate in the CRS planning process by attending a CRS Committee meeting which was held on May 14, One of the agenda items of said meeting was the review of common problems, development policies, mitigation strategies, inconsistencies and conflicts in policies, plans, programs, and regulations. Of the agencies contacted, only the Southwest Florida Water Management District was able to attend. This lack of attendance can be attributed to the fact that all local governments Comprehensive Plans are reviewed by the Department of Community Affairs, the Regional Council, and the Water Management District during the approval process. Given that the CRS Plan was authored to be consistent with the goals, objectives and policies of the Pinellas County Comprehensive Plan, much of this coordination had already taken place. Step 3: As noted, the Pinellas County CRS Plan was authored to be consistent with the goals, objectives and policies of the Pinellas County Comprehensive Plan - which has been reviewed by State and Regional agencies for consistency with their policies and programs. One of the primary functions of the Comprehensive Plan is to address and plan for the future needs of Pinellas County. iv

5 Preface Step 4: On July 6, 1998, a draft of the Action Plan section of this Plan was transmitted to the coordinating agencies which have been previously noted soliciting their comments on or before August 1, Return correspondence was received from FEMA and the Tampa Bay Regional Planning Council. Adoption of the CRS Plan This Plan was adopted by the Pinellas County Board of County Commissioners in September 15, Implementation, Evaluation, and Revision Step 1: The CRS Plan will be evaluated and revised, as necessary, in the form of an annual report. The CRS Plan Annual Report will address changes in baseline conditions stated in the Plan - i.e., number of type of buildings at risk, boundaries of the 100-year floodplain, State and Federal programs, etc. The Annual Report will also provide a description of the implementation status of the Action Plan and identify any problems associated therewith. In addition, the report will provide a summary of any changes which may be necessary or that have occurred to the CRS Plan. The report will be submitted as part of the annual recertification process. Step 2: During the recertification process, the CRS Committee will review the Annual Report - including any changes to the CRS Plan proposed therein - and, if necessary, will recommend changes prior to its approval and transmittal to the Insurance Services Office (ISO) of the Community Ratings System. 5

6 Preface Pinellas County Community Ratings System Floodplain Management Plan TABLE OF CONTENTS I. Introduction 1.1 The Community Ratings System and the Planning Process FEMA and Flood Hazard Mitigation Policy Rationale for Managing Development within the Floodplain II. Hazard Assessment 2.1 Flood Prone Areas Redesignation of the 100-year Floodplain History of Flood Events Resulting in Repetitive Loss Claims Types of Natural Hazards Producing Flood Conditions Types of Hurricanes Storm Damage Potential Storm Surge Vulnerability Analysis: The SLOSH Model Vulnerability to High Winds Repetitive Loss Areas III. Problem Assessment 3.1 The Area-at-Risk Land Uses within the Area-at-Risk Development and Population Trends, Buildings and Facilities at Risk Flood Hazard Awareness and Warning Procedures Evacuation Procedures Public Shelter Analysis Areas Providing Natural and Beneficial Functions Impact of Flooding on Pinellas County

7 Preface IV. Goals of the CRS Plan 4-1 V. Review of Possible Activities 5.1 Preventive Activities Property Protection Activities Activities to Protect the Natural and Beneficial Functions of the Floodplain Emergency Services Activities Structural Projects Public Information Activities VI. Action Plan 6.1 Preventive Actions Property Protection Actions Natural Resource Protection Actions Emergency Services Actions Structural Projects Public Information Actions VII. Post-Disaster Mitigation Policies and Procedures 7.1 Introduction Post-Disaster Redevelopment Task Force Restoration of Essential Services Post-Disaster Building Permit Plan Redevelopment in Coastal High Hazard Areas Redevelopment of Public Facilities and Infrastructure Pinellas County Build Back Policy Criteria for Acquisition of Damaged Land and Property Appendix A Appendix B Appendix C Appendix D Appendix E Storm Events Resulting in NFIP Claims SLOSH Grids Repetitive Loss Maps and Properties 100-year Floodplain in Pinellas County Future Land Use Designations of the Pinellas County Comprehensive Plan 7

8 Preface Appendix F Appendix G Appendix H Appendix I Public Hurricane Evacuation Shelters Map of Natural Areas within the Area-at-Risk Beach Renourishment and Maintenance Projects Structural Flood Mitigation Projects 8

9 Chapter 1: Introduction and Purpose LIST OF TABLES AND FIGURES Tables 2.1 Saffir-Simpson Scale Existing Land Use Acreage within the Area-at-Risk Number and Types of Buildings, Area-at-Risk Housing Units by Type, Area-at-Risk Hospitals Subject to Hurricane Evacuation, Pinellas County Fire Stations within Hurricane Evacuation Zones, Pinellas County Distribution of Future Land Use Designations of Vacant Acreage, Area-at-Risk Storm Categories, Corresponding Evacuation Levels and Potential Tide Heights (Surges) Estimated and Projected Population at Risk, Pinellas County, Estimated and Projected Evacuation Population, Pinellas County, Estimated and Projected Population to Utilize Public Shelter, Pinellas County, Shelters within Hurricane Evacuation Zones, Pinellas County Figures 3.1 Existing Land Uses within the Area-at-Risk

10 Chapter 1: Introduction and Purpose Chapter 1 Introduction and Purpose 10

11 Chapter 1: Introduction and Purpose I. INTRODUCTION and PURPOSE The Community Ratings System and the Planning Process In 1992, the County submitted an application to participate in the Community Rating System (CRS) flood hazard mitigation program - an optional component of the National Flood Insurance Program (NFIP). It is designed to encourage and award communities that undertake public awareness and other floodplain activities beyond the minimum requirements of the NFIP. Municipalities are classified (or rated) within the program by the number of flood damage prevention activities it undertakes. The County s present classification is Class 8. This rating enables residents of the unincorporated county who have flood insurance and live in the Special Flood Hazard Area to receive a 10 percent discount on their flood insurance premiums. The County has initiated an extensive outreach program to inform residents of the NFIP. Credit was also achieved by the County for its floodplain information efforts and its adoption of restrictive development regulations. In conjunction with participating in the CRS, the County adopted the NFIP Repetitive Loss Plan (NFIP Plan) in November, The intent of the NFIP Plan was to encourage those owners of repetitive loss properties to take steps to protect their properties from future damage. The Plan also served to educate and increase awareness of the availability and importance of purchasing flood insurance. For the purposes of the CRS program, repetitive loss properties are defined as those properties that have had more than one insurance claim of greater than $1,000 since Because unincorporated Pinellas County contains more than 10 individual repetitive loss properties, it is labeled a Category C municipality. As such, the County must prepare this CRS Flood Hazard Mitigation Plan (CRS Plan) to replace and/or complement the adopted NFIP Plan. This flood hazard mitigation plan is similar to the NFIP Plan in that it requires policies and strategies to mitigate the loss of life and property due to flooding. However, the CRS Plan has additional requirements and provides for optional activities which can be undertaken during the planning process to improve a community s overall CRS rating. Much like the overall CRS rating, the CRS Plan is evaluated on a points system. With the achievement of points, Pinellas County either improves or advances closer to improving its overall CRS rating. Points are awarded for completing activities concerning the organization of the plan, public involvement, coordination with other agencies, and hazard and problem assessment. In addition, the Plan is to contain goals to complete certain types of preventive activities, an action plan to meet those goals, and a monitoring process in the form of an annual report. The report is among the documentation necessary for recertification into the CRS program, which is also required on an annual basis. 11

12 1.2 - FEMA and Flood Hazard Mitigation Policy Chapter 1: Introduction and Purpose The Flood Insurance Act (Act) of 1968 is the cornerstone of flood damage mitigation policy and its implementation. Its passage was a reaction to a dramatic increase in the number of insurance claims being filed as a result of flood damage. This rise in insurance claims corresponded directly with the escalation of development taking place in areas along shorelines and waterways - such as in Pinellas County. Established in the Act, the Federal Emergency Management Agency (FEMA) is the chief administrative agency for establishing flood mitigation policies and identifying flood-prone areas. The Federal Emergency Management Agency (FEMA) administers the National Flood Insurance Program (NFIP), which was also established in the Act of It provides property owners the opportunity to purchase federally-backed flood insurance within communities that enter into the NFIP. Under the NFIP, FEMA is required to develop flood risk data for use in both insurance rating and floodplain management. Floodplain delineation is based on topography, depth to water table, history of flooding, flow obstructors (natural and man made), and flow accelerators (e.g. vegetation versus parking lots and streets). FEMA develops these data through flood insurance studies (FISs). In FISs, both detailed and approximate analyses are employed. Generally, detailed analyses are used to generate flood risk data only for developed or developing areas within communities. For undeveloped areas where little or no development is expected to occur, FEMA uses approximate analyses to generate flood risk data. In order to implement its participation in the National Flood Insurance Program (NFIP), Pinellas County has adopted a flood damage prevention ordinance which requires that construction and substantial improvements within flood hazard areas meet certain elevation or floodproofing criteria. An example of these criteria is requiring residential buildings within FIRM V zones must be constructed on pilings or columns. Property owners within flood hazard areas and who have federally-subsidized mortgages are required to maintain flood insurance on their structure. In addition, most conventional lenders now require flood insurance for most homes within the 100-year floodplain, as identified by FEMA. Furthermore, Florida Joint Underwriters Association requires flood insurance prior to the issuance of a homeowner s policy. Every municipality in Pinellas County in the flood hazard area participates in the NFIP. 12

13 1.3 - Rationale for Managing Development within the Floodplain Chapter 2: Hazard Assessment There are various economic and social reasons for regulating development within known floodplains. Development of flood-prone lands and improper management of flood waters is inconsistent with their natural functions and can have significant adverse impacts upon the health, safety, and welfare of the community. These potential impacts include: a. The owners of homes and business structures located in frequently flooded areas and their customers, guests, employees, children, and future generations are subjected to unreasonable risk of personal injury and property damage; b. Expensive and dangerous search and rescue and disaster relief operations must be conducted when developed properties are flooded; c. Roads and utilities associated with development are subject to damage from flooding at great expense to taxpayers and rate payers; d. Flooding of developed properties leads to demands for governments to construct expensive and environmentally damaging projects to control flood waters; e. Loss of natural water storage capacity leads to reduction in available water supply; f. The level, velocity, frequency, and duration of flooding on other lands are often increased when flood waters are obstructed, diverted, displaced, or channelized; g. Water quality is degraded, freshwater inflows to estuaries are disrupted and habitats are lost; and h. Property values are lowered and economic activity is disrupted by damaging floods. In order to provide development where possible without endangering the health, safety, and welfare of persons living in flood-prone areas, several programs have been instituted at the federal, state, and local levels. The CRS is one such program. Other floodplain management programs are inventoried in Section 5.2, herein. 13

14 Chapter 2: Hazard Assessment Chapter 2 Assessment of Potential Hazards 14

15 Chapter 2: Hazard Assessment II. ASSESSMENT OF POTENTIAL HAZARDS Flood Prone Areas Pinellas County is a relatively flat peninsula separating the Gulf of Mexico from Tampa Bay. As such, it is particularly vulnerable to flooding caused by hurricanes and tropical storm activity. The primary factors which contribute to flooding within the County are: 1) Heavy rainfall; 2) Storm surge; and 3) Inadequate drainage systems unable to accommodate the rainfall generated by these storms. These topographical and meteorological factors make the coastal areas as well as inland areas along the County s creeks and drainage ways vulnerable to flooding. As enumerated in Section 2.2, all of the flood damage previously incurred within unincorporated Pinellas County has exclusively been the result of the factors listed above. Flood-prone areas within Pinellas County are categorized by FEMA into two designations. One such designation is the 100-year floodplain, which are referred to on the FIRM as A-Zones. Areas designated within A-Zones are those which have topographical and locational characteristics which lend them favorable for flood activity. Based on historical data, it is assumed that these areas have a one-percent chance of experiencing flooding in any given year. Another FEMA designation representing a floodplain is the velocity zone, or V-Zone. This designation is for those coastal areas within the 100-year floodplain which are most susceptible to flood damage as a result the wave velocity of storm surge. A map of these areas for both incorporated and unincorporated areas of Pinellas County is provided in Appendix D Redesignation of the 100-year Floodplain During the formulation of this document, the boundaries for designated flood zones, including the 100-year floodplain, were under revision by FEMA. The current flood zone maps for most of the County had not been updated since FEMA utilized surveys and data collected by the State of Florida Department of Environmental Protection (FDEP) as a basis for updated flood zone boundary maps which were drafted in early Originally, the County had until the end of April to comment on FEMA s proposed maps; however, opposition in Pinellas County to the proposed maps was strong enough to warrant an extension of this deadline until September In order to ensure the validity of FDEP findings, the Pinellas County Board of County Commissioners, in cooperation with various municipalities throughout the County, contracted the University of Florida to perform Aerial Topographic Mapping of the County. 15

16 Chapter 2: Hazard Assessment The primary tool utilized for this technology is the Airborne Laser Mapper, an instrument which is attached to an aircraft that is monitored by a satellite. The laser equipment discharges pulses of infrared light from the aircraft, at a rate of 5,000 pulses per second, which strike objects on the ground. By applying the time it takes for the laser pulses to make contact with an object on the ground to the altitude and speed of the aircraft, a computer program can derive the topography and elevation of the area being surveyed in great detail. Engineers plan to survey some of the terrain from ground level to ensure findings from the laser technology, known as LIDAR, are accurate. It should be noted that these results will not only be used for evaluating flood hazards. They will also be utilized to evaluate the design and scope of various roadway and drainage projects. Furthermore, these results will be employed by the Pinellas County Department of Emergency Management to reconsider the boundaries of hurricane evacuation zones and, thus, the Coastal High Hazard Area. Once this survey has been completed, the results will be submitted to FEMA for their consideration. These survey results, in conjunction with the aforementioned data collected by FDEP, will be the primary data sources for the updated flood zone boundary maps for both incorporated and unincorporated areas of Pinellas County. Any changes to the Pinellas County resulting from the new FEMA maps, which are expected to be finalized by 1999, will be incorporated into the document via the annual report process provided within the CRS program History of Flood Events Resulting in Repetitive Loss Claims During the 19th century, two hurricanes made landfall in Pinellas County causing widespread destruction and altering the land forms of some of its barrier islands. The first major flood event during the 20th century was an unnamed Category 3 Hurricane which made landfall the Ozona/Tarpon Springs area on October 24, Although destruction from these storms was widespread, the overall damage was minimal primarily due to the lack of development and infrastructure present within affected areas when the storms occurred. Since then, there has been a high influx of population and urban development throughout Pinellas County with a strong attraction to waterfront development. If there had been a perceived danger from flooding, much of this growth would have been directed away from flood-prone areas. However, this did not occur according to existing land use patterns throughout the County. Until Pinellas County adopted a flood damage prevention ordinance in 1977, and a floodplain management ordinance in 1983, development had taken place with minimal regard for flooding potential. As a result of this disregard, many areas of Pinellas County, both incorporated and unincorporated, are vulnerable to major losses from hurricanes and other natural disasters. With the creation of the NFIP and FEMA in 1968, the uniformity and accuracy in the collection of data concerning flood events and the magnitude of their damage increased dramatically. Data collected prior to that time was poorly organized and/or documented. 16

17 Chapter 2: Hazard Assessment Pursuant to information provided by the National Weather Service and the Pinellas County Department of Emergency Management, the weather events that were included in NFIP repetitive loss reports from May 1979 through December 1997 are provided in Appendix A. Discussion of the impacts of the more severe of these flood events is provided in Section 3.8 herein Types of Natural Hazards Producing Flood Conditions Because of its topography and location, Pinellas County is not vulnerable to geologicallyoriented natural hazards such as earthquakes, mudslides and flash floods. However, the County is vulnerable to those natural hazards resulting from hurricanes or other varieties of tropical storm activity. The National Weather Service has identified the Tampa Bay Area as one of the most vulnerable areas to hurricanes in the United States. This is noteworthy for Pinellas County because much of the population resides in low-lying areas and/or mobile homes which are subject to the storm surge and high wind effects of hurricanes. The most recent hurricane to impact Pinellas County was Hurricane Elena in Although the center, or eye, remained more than 80 miles out in the Gulf of Mexico and never made landfall on the west coast of Florida, damage reports from Florida submitted to the State Division of Emergency Management estimated nearly $73 million in private property damage and $27 million in public property damage. As Appendix A indicates, winter storms have periodically resulted in property damage as well. In 1992, a winter storm commonly referred to as the No- Name Storm brought severe flooding and wind damage to many areas within Pinellas County. With proper planning and implementation of FEMA regulations, these types of damages can be reduced. The two major hazards associated with hurricanes and tropical storms are the storm surge and high winds. Both of these hazards can be experienced in a hurricane; however, each hazard can affect the County independently through tropical storms, winter storms and localized tornadoes as a result of thunderstorm activity Storm Surge Storm surge is the abnormal rise in sea level caused by the circular winds and low [barometric] pressure in or around the center of a hurricane or tropical storm. The occurrence of a severe coastal storm causes tidal flooding as a result of storm surge. Storm surge produces most of the flood damage and drowning associated with storms that make landfall or that closely approach the coastline. According to the National Hurricane Center, the storm surge is the most dangerous of the hurricane hazards with nine out of ten hurricane-related deaths caused by drowning. The height of the storm surge and, hence, the distance of landward inundation is a function of several variables which include the barometric pressure, the height of tide at landfall, and the amount of rainfall. As barometric pressure at the center of the storm decreases, the corresponding storm 17

18 Chapter 2: Hazard Assessment surge increases. Landfall at high tide also increases storm surge levels. Due to its relatively flat topography, Pinellas County has not experienced high freshwater levels as a result of alluvial fan flooding, flash flooding or fluctuation levels within its freshwater bodies. However, the coincidental occurrence of extremely high tides with heavy amounts of rainfall can block stormwater outfalls and produce minor localized flooding High Winds The high winds also can have a devastating effect on persons outside, in mobile homes, in unsound, substandard structures or in structures with unprotected windows or doors. In 1986, a study by the Tampa Bay Regional Council (TBRC) concluded that winds play a significant impact in property damage and potential injury and loss of life. For example, while a fullyengineered multi-story structure could withstand the storm surge of a major storm, without protection on the windows and other cladding, occupants within any structure would be at serious risk. This holds true for all types of structures exposed to sustained winds in excess of 115 mph. Hurricane Andrew in 1992 provided the most disastrous example of structural vulnerability to winds, damaging more than 300,000 homes in south Dade County and resulting in 25 billion dollars in property damage statewide Tornadoes Tornadoes occasionally occur as a result of thunderstorm activity. Hurricane experts who examined the aftermath of Hurricane Andrew concluded that tornadoes were spawned from the eye wall of that storm. Winds from these tornadoes were estimated to be in excess of 250 miles per hour. Within just a few minutes, five people were killed and approximately 300 homes were destroyed. In October 1992, three tornadoes touched down in the Pinellas County which resulted in a national disaster declaration Types of Hurricanes The following types of hurricanes are differentiated by orientation to the effected land mass upon approach of the storm. 1) Landfalling: A hurricane characterized by the track of its eye approaching from water to land and continuing inland, as in a storm striking the west coast of Florida. This type is generally the most threatening to life and property. 2) Paralleling: A hurricane characterized by the track of its eye approaching but not crossing the coastline, often moving parallel against the shore. Such a storm would be one that moves northwest along the Gulf Coast of Florida. These storms - such as Hurricane Elena - often produce significant hurricane hazards even though they do not make landfall. 18

19 Chapter 2: Hazard Assessment 3) Exiting: A hurricane that is characterized by its return to open water after traversing a significant land mass, as in a storm entering along the east coast of the Florida peninsula and exiting on the west coast. The dynamics of this type of hurricane are such that they lose their strength over land Storm Damage Potential The Saffir-Simpson Hurricane Scale is used by the National Weather Service to give local officials a continuing assessment of the potential wind and storm surge damage from a hurricane in progress. The Scale numbers are made available to decision makers when a hurricane is within 72 hours of landfall. As the hurricane approaches, the Scale assessments are revised regularly pursuant to changing observations. Due to a shallow, sloping bottom which extends well offshore from the coastline, storm surge values for Pinellas County are projected to be higher than that indicated on the general Saffir-Simpson Scale. The five categories of a hurricane and the resulting hazard potential, including the storm surge heights, are shown below in Table 2.1. TABLE 2.1 SAFFIR-SIMPSON SCALE Hurricane Category Central Pressure in Millibars Central Pressure in Inches Winds (Miles per Hour) Storm Tide (Feet above Sea Level)* 1 > 980 > ' ' ' ' 5 < 920 < ' * Represents specific predicted values for Pinellas County 19

20 Chapter 2: Hazard Assessment Damage Potential of Hurricanes (Saffir-Simpson Scale) Category 1: Damage to foliage and trees, unanchored mobile homes, minimal damage to other structures; flooding of barrier islands and coastal roads, minor pier damage; and small crafts torn from moorings. Category 2: Considerable damage to trees/foliage; major damage to mobile homes, building roofs, windows and doors; considerable damage to marinas, piers and small crafts; and flooding. Category 3: Large trees and signs blown down; some damage to roofing materials, windows, and doors; small buildings and mobile homes destroyed; serious flooding along barrier islands/coast; and large and small structures destroyed by waves and/or floating debris. Category 4: Trees and signs blown down; extensive damage to roofing materials, windows, and doors; complete destruction of mobile homes; major damage to lower floors of structures near the coast and/or barrier islands due to flooding, waves and/or floating debris. Category 5: Trees blown down; extensive damage to roofs; all signs down; building failures; complete destruction of mobile homes; major damage to lower floors of structures less than 15 feet above sea level in storm surge zones Storm Surge Vulnerability Analysis: The SLOSH Model The principal tool utilized for analyzing the expected storm surge from potential hurricanes affecting the study area is the Sea, Lake and Overland Surges from Hurricane (SLOSH) numerical storm surge prediction model. The SLOSH computerized model predicts the tidal surge heights that result from hypothetical hurricanes with selected various combinations of pressure, size, forward speed, track and winds. Originally developed for use by the National Hurricane Center (NHC) as a tool to give geographically-specific warnings of expected surge heights during the approach of hurricanes, the SLOSH model is utilized for local hazard and vulnerability analyses as well. The first Tampa Bay SLOSH model was completed in 1979 and represented the first application of SLOSH storm surge dynamics to a major coastal area of the United States. This model was created by the Techniques Development Lab of the National Oceanic and Atmospheric Administration (NOAA). The SLOSH model was developed for individual geographic coastal areas, incorporating the unique local bay and river configuration, water depths, bridges, roads, 20

21 Chapter 2: Hazard Assessment and other physical features. In addition to open coastline heights, one of the most valuable outputs of the SLOSH model for hazard assessment is its prediction of surge heights over land, thus predicting the most landward run-up of the surge into inland areas. In December 1990 the National Hurricane Center developed a new SLOSH model for the Tampa Bay Area. A major improvement to the model was the incorporation of wind speed degradation over land as the simulated storms moved inland. This duplicated the pressure change and increases in the radii of maximum winds as the hurricane weakens after making landfall. The grid configuration of the updated SLOSH model also provided for tropical storm scenarios (55-74 mph sustained winds) Storm Surge Potential The Tampa Bay SLOSH model is an elliptical grid as its unit of analysis with 90 arc lengths and 101 radials. Use of the grid configuration allows for individual calculations per grid square which is beneficial because it provides increased resolution of the storm surge at the coastline and inside the harbors, bays and rivers, while decreasing the resolution in the deep water where detail is less important. Each grid in the model contains approximately 5.6 square miles (See Appendix B). The maximum surge heights are plotted by storm track and tropical storm / hurricane category. These plots of storm surge heights for a given storm category and track are referred to by the model as reference hurricanes. The reference hurricanes are used in evacuation decision making when and if sufficient forecast information is available to project the storm track and type of storm. Reference hurricanes can be categorized into 55 type/intensity groups. In turn, each of these groups, through SLOSH analysis, is determined to confront each coastal municipality with one of three evacuation scenarios. These scenarios are discussed in further detail in Section 3.6, herein. Under each evacuation level, all mobile home residents and certain areas must be completely evacuated. Pinellas County is represented by 491 SLOSH grids which are listed by their coordinates in the model. SLOSH grids for Pinellas County and their corresponding predicted storm surge heights for landfalling and exiting storms are provided in Appendix B Vulnerability to High Winds The primary mitigation measure against the hazard of high-velocity winds is the adoption and enforcement of building codes that reflect adequate wind load criteria, protect against flying debris and building envelope penetration, and are enforced through proper inspections and trained personnel. 21

22 Chapter 2: Hazard Assessment When Hurricane Andrew struck in 1992, it generated high winds and rain over a vast area of Dade County. Although the storm produced high storm surge levels (16+ feet MSL), the effects of storm surge and wave action were limited to a relatively small area of the coastal floodplain. However, it was evident from the extensive damaged caused by wind that wind speeds were significant. After Hurricane Andrew, FEMA assembled a Building Performance Assessment Team to survey the performance of structures in the storm s path and provide findings and recommendations to both the Interagency Hazard Mitigation Team and the Dade County Building Code Task Force. The findings of the survey team are critical to every community vulnerable to hurricanes, and recommendations have been incorporated into Hazard Mitigation and Post-Disaster Redevelopment Plans statewide. In summary, the following major findings were made: In general, masonry buildings and wood-frame modular buildings performed well. The breaching of the building envelope by failure of openings (e.g., doors, windows) due to debris impact was a significant factor in the damage to many buildings. This allowed an uncontrolled buildup of internal air pressure that resulted in further deterioration of the building s integrity. Total failure of manufactured homes in the affected area. Failure of manufactured homes and other metal-clad buildings generated significant missile debris. Loss of roof cladding was the most pervasive type of damage to buildings - primarily due to the failure of the method of attachment and/or material, inadequate design, inadequate workmanship and missile (debris) impact. Much of the damage to residential structures also resulted from inadequate design, substandard workmanship and/or misapplication of various building materials. Inadequate design for load transfer was found to be a major cause of the observed structural failure of buildings. (In adequately designed buildings, the wind load transfer path is clearly defined. Proper connections between critical components allow for the safe transfer of loads that is required for structural stability. Where high quality workmanship was observed, the performance of buildings was significantly improved.) Inadequate municipal review of construction permit documents. 22

23 Chapter 3: Problem Assessment Mitigation measures including building code amendments, state required certification for building department personnel, increased inspections and additional state and federal regulations, have been identified to specifically address each of these major findings and recommendations. In addition, the Legislature strengthened the provisions of Chapter 468, F.S., by requiring minimum qualifications for building code administrators and inspectors Repetitive Loss Areas Since 1978, the NFIP has insured more than 2.5 million buildings throughout the United States. However, damages to 2% of insured buildings accounted for approximately one-third of insurance losses resulting from the same properties having been flooded on multiple occasions. Consequently, FEMA has placed special emphasis on minimizing claims on repetitive loss properties. The Federal Insurance Agency has listed 50 properties throughout unincorporated Pinellas County which are considered repetitive loss properties. In order to be classified as such, two or more claims of more than $1,000 have to been paid by the NFIP since Each repetitive loss property has been plotted on a countywide map to view the probable relationships which are common between them and the relationships with physical features of the County such as canals, creeks, tidal swamps, coastal areas and drainage basins. Seven areas of one or more repetitive loss properties have been identified and labeled repetitive loss areas. These areas are Augusta Avenue (Palm Harbor), Avery Bayou, Crystal Beach, Sutherland Bayou, Ozona, Tinney Creek, and Masters Bayou. A complete list of and map depicting repetitive loss properties are provided in Appendix C. 23

24 Chapter 3: Problem Assessment Chapter 3 Problem Assessment 24

25 Chapter 3: Problem Assessment III. PROBLEM ASSESSMENT The Area-at-Risk Given its relatively flat topography and proximity to the Gulf of Mexico, it can be expected that portions of Pinellas County would be vulnerable to flooding. Pursuant to the Flood Insurance Rate Map (FIRM), over 21,785 acres of unincorporated Pinellas County is within V and A Zones. This represents nearly one-third (32.5%) of the total unincorporated area of Pinellas County. These areas are within the 100-year floodplain and subject to the flood hazard identified in Part II of this Plan. Management policies of incorporated areas of the floodplain are primarily the responsibility of the municipalities in which they are situated. Areas of the 100-year floodplain within these municipalities are subject to the regulations and floodplain management plans thereof. In order to plan for unincorporated areas, it is necessary to distinguish the 100-year floodplain for the entire County from that of the unincorporated areas. In order to do so, the unincorporated portions of the 100-year floodplain are collectively identified and referred to herein as the area-at-risk. The 100-year floodplain within Pinellas County is represented in the map attached hereto as Appendix D Land Uses within the Area-at-Risk All types of land uses are present within the area-at-risk. Fortunately, the more prevalent land uses fall under the category of conservation/ preservation. This land use category generally consists of environmentally sensitive areas and is typically protected from the encroachment of development. This not only reduces the current flood hazard, but also minimizes it in the future as Pinellas County continues to develop. Over one-fourth (26.5 %) of the area-at-risk is designated for preservation/ conservation. Another predominant land use within the area-at-risk is recreation/open space. This stands to reason given that shorelines of waterbodies usually are typically prime recreational locations as well as floodprone areas. Recreation/open space acreage, composed mainly of golf courses and public parks, makes up 14.8 percent of the areaat-risk. Therefore, the conjunction of recreation and preservation acreage represents over 40 percent of the area-at-risk being characterized by minimal or no development. The most prevailing land use within unincorporated Pinellas County overall, single-family residential land uses are the second most common within the area-at-risk. Single-family residential acreage accounted for 19.4 percent of its total area. The percentages of other residential uses in the areaat-risk, such as mobile homes and multifamily housing, are consistent with those of the entire unincorporated County. Both commercial and industrial acreage are less prevalent in the area-atrisk than in the unincorporated County as a whole. 25

26 Chapter 3: Problem Assessment Land use acreage distribution within the area-at-risk is represented in Table 3.1 and Figure 3.1. TABLE 3.1 Existing Land Use Acreage in the Area-at-Risk March 1998 Land Use Acreage Single-Family Residential 4,229 Multifamily Residential 1,038 Duplex / Triplex 197 Mobile Homes 607 Commercial 675 Industrial 505 Public / Semi-Public 2,150 Agriculture 359 Recreation / Open Space 3,217 Conservation / Preservation 5,762 Miscellaneous 440 Vacant 2,608 Total Acreage 21,787 Source: Pinellas County Planning Department, Development and Population Trends, Buildings and Facilities at Risk It is necessary in assessing the problem to quantify evacuation times as well as hurricane response. In order to do this, it is essential to identify the number of people that will need to be evacuated from the specific vulnerable zones. This includes identifying the population residing within the area-at-risk and, thus, those required to evacuate from storm surge flood hazard pursuant to the SLOSH model (See Appendix B). It also entails distinguishing the number and types of buildings and critical facilities - such as fire stations and hospitals - that are prone to flooding. The identification of these populations and facilities are critical in the implementation of successful hazard mitigation and floodplain management policies. 26

27 Chapter 3: Problem Assessment Insert Figure

28 Chapter 3: Problem Assessment Back of Figure

29 Chapter 3: Problem Assessment Number and Types of Buildings at Risk In order to determine the number and types of buildings within the area-at-risk, the number of varying types of structures were inventoried and then applied to the percentage of overall acreage of existing land use types within the area-at-risk. For example, if there were 58 single-family structures situated on 24 acres, and half of this acreage had been identified as being within the area-at-risk, then the estimated number of single-family structures would be half of the total number of structures, or 29. This methodology was also applied to estimate the number of structures utilized for multifamily residential, commercial, recreational, industrial, and public/semi-public uses, as well as mobile homes. The results of this application are provided in the table below. As Table 3.2 illustrates, over 56 percent of the structures at risk to the 100-year flood are single-family homes. A significant amount of structures also at risk are mobile homes - which constitute almost 25 percent of the total structures at risk. The remaining 19 percent of structures within the 100-year floodplain are evenly distributed among multifamily residential, commercial, industrial, recreational, conservation, and public/semi-public uses. TABLE 3.2 Number and Types of Buildings Area-at-Risk Type of Building Number Percentage Single-Family Homes 8, Multifamily* 1, Mobile Homes 3, Commercial Industrial Public / Semi-Public Recreation Conservation / Preservation Agriculture TOTAL 15, *also includes duplexes and triplexes Source: Pinellas County Planning Department,

30 Chapter 3: Problem Assessment Housing Units within the Area-at-Risk The number of single-family and mobile home units within the area-at-risk is the same as the number of structures presented in Table 3.2. However, the number of units per multifamily structure varies. In order to calculate an estimate of multifamily units, the percentage of the total multifamily acreage situated within the area-at-risk was applied to the total number of multifamily units, including duplexes and triplexes present within the area-at-risk. For example, if 40 percent of the multifamily acreage within a given sample area was situated within the areaat-risk and that sample area contained a total of 100 units, it was assumed that 40 of these units are situated within the area-at-risk. By applying this methodology and transferring the single family and mobile home data from Table 3.2, the estimated number of housing units within the area-at-risk is provided in Table 3.3. TABLE 3.3 Housing Units by Type within the Area-at-Risk March, 1998 Unit Type Estimated Number of Units Percentage Single Family 8, Multifamily* 12, Mobile Homes 3, Total 25, *includes duplexes and triplexes Source: Pinellas County Planning Department, Population Residing Within the Area-at-Risk A estimate of the population residing within the area-at-risk can be ascertained by applying the total number of housing units by the number of persons per household. In 1990, the U.S. Census reported an average household size of 2.32 persons per household in unincorporated Pinellas County. By applying the 1990 Census figure to the estimated number of housing units provided in Table 3.3, the population residing in the area-at-risk would be 58,902. This figure represents 21.2 percent of the estimated population of 278,264 for unincorporated Pinellas County. 30

31 Chapter 3: Problem Assessment Hospitals Because hospitals typically serve residents from all parts of Pinellas County, the inventory of hospitals includes those in both the incorporated and unincorporated areas of the County which are within evacuation zones. According to the Pinellas County Department of Emergency Management, there are six Pinellas County hospitals which must evacuate due to hurricane vulnerability. The hospitals vulnerable to storm surge during a major storm event are listed in Table 3.4. TABLE 3.4 Hospitals Subject to Hurricane Evacuation Pinellas County Hospital Address Capacity Vulnerability* Horizon Hospital St. Petersburg Medical Center Palms of Pasadena Hospital Vencor Hospital Suncoast Hospital VA Medical Center U.S. 19 South Clearwater, FL th Avenue North St. Petersburg, FL Pasadena Avenue South St. Petersburg, FL th Street South St. Petersburg, FL Indian Rocks Road Largo, FL Bay Pines Boulevard Bay Pines, FL Category Category Category Category Category Category 4 * Represents the minimal storm event necessary for vulnerability to storm surge. Source: Pinellas County Department of Emergency Management,

32 Chapter 3: Problem Assessment Fire/EMS Stations Because individual Fire Districts within Pinellas County often include both unincorporated and incorporated areas, the inventory of vulnerable fire/ems stations was done on a countywide basis. Their vulnerability to flooding was measured by their presence in an evacuation zone. Pursuant to data from the Pinellas County Department of Emergency Management, there are 59 Fire/EMS Stations throughout Pinellas County. Of these, 35 are located within evacuation zones. The vulnerability of these stations varies from a Category 1 to a Category 5 storm event. Given that a significant portion of the Pinellas County population resides within evacuation zones, some level of vulnerability is inevitable due to the inherent need of these facilities to be located in close proximity to their intended service populations. The most vulnerable stations are those on the barrier islands and close to the shoreline areas of St. Petersburg - which are mostly incorporated areas. An inventory of fire/ EMS stations throughout the County that are vulnerable to flooding is provided in Table 3.5. TABLE 3.5 Fire Stations within Evacuation Zones Pinellas County Station Number Address Vulnerability* Pinellas Bay Way, St. Petersburg Category th Street North, St. Petersburg Category th Street North, St. Petersburg Category st Street South, St. Petersburg Category Bayou Grande Boulevard, St. Petersburg Category Roosevelt Boulevard, St. Petersburg Category Spadco Drive, Clearwater Category rd Avenue South, St. Petersburg Category th Avenue North, St. Petersburg Category Oleander Way South, South Pasadena Category Pass-a-Grille Way, St. Pete Beach Category Gulf Boulevard, St. Pete Beach Category th Avenue, Treasure Island Category Municipal Way, Madeira Beach Category 1 32