MITIGATION ASSESSMENT TEAM REPORT Hurricane Ivan in Alabama and Florida Observations, Recommendations, and Technical Guidance FEMA 489 /August 2005 Executive Summary Hurricane Ivan made landfall on Thursday, September 16, 2004, just west of Gulf Shores, Alabama. The hurricane brought 1-minute sustained wind speeds (over open water) of 121 miles per hour (mph) (as estimated by the National Hurricane Center [NHC]), torrential rains, coastal storm surge flooding of 10 to 16 feet above normal high tide, and large and battering waves along the western Florida Panhandle and Alabama coastline. In its Tropical Cyclone Report, Hurricane Ivan, 2-26 September 2004 (NHC, 16 December 2004, Revised 6 January 2005), the NHC categorized Hurricane Ivan as a Category 3 hurricane, as measured by the Saffir- Simpson Hurricane Scale. The National Weather Service reported that from September 15 through 16, Ivan spawned 23 tornadoes in Florida and produced as much as 10 to 15 inches of rainfall in some areas (National Weather Service Mobile – Pensacola, “Powerful Hurricane Ivan Slams the US Central Gulf Coast as Upper Category-3 Storm,” www.srh.noaa.gov/mob/ivan_page/Ivan-main.htm). After landfall, Hurricane Ivan gradually weakened over the next week, moving northeastward over the Southeastern United States and eventually emerging off the Delmarva Peninsula as an extratropical low on September 19, 2004. On September 18, 2005, the Federal Emergency Management Agency’s (FEMA’s) Mitigation Division deployed a Mitigation Assessment Team (MAT) to Alabama and Florida to evaluate building performance during Hurricane Ivan and the adequacy of current building codes, other construction requirements, and building practices and materials. This report presents the MAT’s observations, conclusions, and recommendations as a result of those field investigations. Several maps in Chapter 1 illustrate the path of the storm, the depth of storm surge along the path, and the wind field estimates. Hurricane Ivan approximated a design flood event on the barrier islands and exceeded design flood conditions in sound and back bay areas. This provided a good opportunity to assess the adequacy of National Flood Insurance Program (NFIP) floodplain management requirements as well as current construction practices in resisting storm surge and wave damage. FEMA was particularly interested in evaluating damages to buildings in coastal A Zones where V-Zone construction methods are not required. Although the NHC categorized Hurricane Ivan as a Category 3 hurricane, surface observation sites throughout the coastal region provided data that indicate that most of the region impacted by the storm likely experienced Category 1 intensity winds with some areas near the Alabama-Florida border experiencing Category 2 intensity winds. None of the surface wind measurements for overland conditions correspond to Category 3 intensity winds. Although Hurricane Ivan was not a design wind event when analyzed with respect to the 2001 Florida Building Code (FBC) or the 2000/2003 International Building Code (IBC) and International Residential Code (IRC), it caused extensive wind-related damage to buildings constructed under earlier codes. Floodplain Management Regulations in Alabama and Florida All of the communities visited by the MAT participate in the NFIP and have adopted floodplain management regulations that meet or exceed minimum NFIP requirements. Up until 2000, these requirements generally were contained only in community floodplain management ordinances. Starting in 2000, however, flood- resistant provisions and floodplain management requirements began to be incorporated into model building codes used in the affected areas (e.g., the IBC, the IRC, and the FBC). The MAT determined that the area flooded by Ivan exceeded the Special Flood Hazard Area (SFHA) shown on the effective Flood Insurance Rate Maps (FIRMs) for many communities, from Gulf Shores, Alabama, to Okaloosa County, Florida, and that flood elevations in many areas exceeded the 100-year Base Flood Elevations (BFEs) depicted on the FIRMs by 2 to 4 feet. The initial flood studies for these communities were completed in the mid 1970s and were based on National Oceanographic and Atmospheric Administration (NOAA) tide gauge frequency analyses. The next studies were completed in the mid 1980s and were based on FEMA’s storm surge model. This second round of flood studies also mapped wave crest elevations (as opposed to stillwater elevations), due in large part to observed damages to new construction at the time of Hurricane Frederic (1979). For the most part, this second round of studies resulted in decreased BFEs and a smaller SFHA when compared to the studies completed in the 1970s. The most recent flood studies were completed in the late 1990s (after Hurricane Opal) and added wave setup and extended the V Zone to include the primary frontal dune. The most recent studies generally increased the BFEs and the SFHA when compared to the studies completed in the 1980s, but not to the extent of the studies from the 1970s. The coastal FIRM changes over time likely resulted in a variety of coastal construction practices over the years, as most buildings were constructed to the minimum regulatory requirements, and could have contributed to flood and erosion damages the MAT observed. Building Codes and Standards in Alabama and Florida Alabama adopts building codes on a statewide basis only for state-owned buildings, such as schools. Local jurisdictions determine the adoption of building codes for private buildings. All Alabama jurisdictions have traditionally adopted editions of the Standard Building Code (SBC) published by the Southern Building Code Congress International. The City of Orange Beach adopted the 2003 IBC in the summer of 2004, just prior to Hurricane Ivan. The City of Gulf Shores adopted the 2003 IBC as an emergency measure after Hurricane Ivan – to improve the quality of the reconstruction. Most other affected Alabama communities, such as those in unincorporated Baldwin County, were still enforcing the 1997 or 1999 SBC at the time of Hurricane Ivan. In the Florida Panhandle, the SBC – with local amendments – was used to regulate construction until early 2002 when the FBC 2001 Edition was adopted statewide. The FBC, administered by the Florida Building Commission, governs the design and construction of residential and non-residential (commercial, industrial, critical/essential, etc.) buildings in Florida. In December 2004, the Florida Building Commission completed the 2004 Edition of the FBC. However, additional changes to the 2004 Edition are being made in response to the 2004 hurricanes, and the 2004 Edition will not replace the earlier edition until fall 2005. Buildings constructed along Florida’s Gulf of Mexico shoreline were also subject to the provisions of the state’s Coastal Construction Control Line, which have been incorporated into the FBC. Damage Assessment Observations Flood Because Hurricane Ivan approximated or exceeded a design flood event, the resultant storm damage provides valuable evidence about the adequacy of NFIP maps, floodplain management requirements, the reliability of the A-Zone delineation in coastal areas, building codes, and design practices. Flood levels from Hurricane Ivan exceeded the mapped BFEs throughout many bays and sounds by several feet. Flood levels along Gulf-front shorelines also exceeded the mapped BFEs but to a lesser extent, and the flooding extended beyond the SFHAs in most communities investigated. Many of the barrier islands were submerged and overwashed. Buildings constructed before the adoption of the NFIP and many buildings located outside the SFHA were severely impacted by the high storm- surge elevations and increased inundation area caused by Ivan. Floodborne debris and wave damage (characteristic of V-Zone damage) was extensive in A Zones, especially along bay and sound shorelines. Floodborne debris from buildings, docks, and piers destroyed lower-level enclosures, stairs, and some buildings. Buildings that were not elevated above the wave crest elevation were damaged during Ivan not only by storm surge, but also by waves and floodborne debris. Erosion was severe along the barrier islands of Alabama and Florida. Areas that had wide beaches and dunes before Ivan were less impacted than those with smaller, narrower beaches and dunes. Erosion along bay and sound shorelines was generally minimal, and structural damage there was predominantly due to storm surge, waves, and floodborne debris. The erosion along the barrier islands undermined shallow foundations and caused many buildings to collapse. Many areas had suffered beach and dune erosion during past coastal storm events, which made the buildings in those areas more vulnerable to flood and erosion impacts from Ivan. Wind Although structural system failures tend to be perceived by the public and the building industry as the dominant issue of concern, it is clear that for buildings built in accordance with the 2001 FBC or the 2000/2003 IBC, structural issues have, in general, been addressed by the codes. Now, the arena in which improvements can and must be made are those related to water intrusion and integrity of the building envelope. Protecting the integrity of the building envelope is important not only to minimize losses and damages to building contents, but also to prevent full internal pressurization and progressive failure of buildings. Extensive damage to the building envelope with associated minor structural system damage was observed at many residential buildings even though Hurricane Ivan was not considered to be a design wind event when evaluating wind speeds and wind pressures from the 2001 FBC or the 2000/2003 IBC and IRC. However, in the areas around Gulf Shores, Orange Beach, and Pensacola Beach, existing building stock constructed to the 1979 to 1997 SBC can be said to have experienced a design wind event, and, thus, damage observed is related to the design parameters used at the times these codes were enforced. Widespread building envelope damage was observed by the MAT throughout the affected area. Performance of building envelopes was generally poor and led to widespread damage to the interiors of residences, businesses, and critical/essential facilities. Windborne debris damage was not widespread. ASCE 7 predicts that significant windborne debris damage will begin in the 120-mph range in inland areas and in the 110-mph range when buildings are within one mile of the coast. Since Ivan’s gust speeds were generally below that level, it is expected that glazing damage during Ivan would be less common than in other more powerful storms such as Hurricane Charley. Given that the actual wind speeds were below current code level wind speeds, the occasional damage to the structural elements and the widespread damage to building envelopes can be characterized as wind-related damage caused by inadequate design, old construction methods, outdated design codes and methods, lack of maintenance, and/or poor construction/code enforcement. Wind damage to the contents of residential and commercial buildings, and critical/essential facilities due to these failures is preventable. Recommendations The recommendations in this report are based solely on the observations and conclusions of the MAT, and are intended to assist the State of Alabama, the State of Florida, local communities, businesses, and individuals in the reconstruction process and to help reduce damage and impact from future natural events similar to Hurricane Ivan. The report and recommendations also will help FEMA assess the adequacy of its flood hazard mapping and floodplain management requirements and determine whether changes are needed or additional guidance required. The general recommendations are presented in Sections 8.1 and 8.2. They relate to policies and education/outreach that are needed to ensure that designers, contractors, and building officials understand the requirements for disaster-resistant construction in hurricane-prone regions. Proposed changes to codes and standards are presented in Section 8.3. Specific recommendations for improving the performance of the building structural system and envelope, and the protection of critical and essential facilities (to prevent loss of function) are provided in Chapter 8. Implementing these specific recommendations, in combination with the general recommendations of Section 8.1 and 8.2 and the code and standard recommendations of Section 8.3, will significantly improve the ability of buildings to resist damage from hurricanes. Recommendations specific to structural issues, building envelope issues, critical and essential facilities, and education and outreach have also been provided. As the people of Alabama and Florida rebuild their lives, homes, and businesses, there are a number of ways they can minimize the effects of future hurricanes, including: Flood-related --Elevate all new construction (including substantially improved structures and replacement of substantially damaged structures) in coastal A Zones with the bottom of the lowest horizontal supporting member above the base flood level. --Require freeboard for all structures in all flood hazard zones with the amount varying with building importance (see ASCE 7-05 and ASCE 24-05 for building importance classification and freeboard requirements) and anticipated exposure to wave effects. --Require V-Zone design and construction for new construction in coastal A Zones subject to erosion, scour, velocity flow, and/or wave heights greater than 1.5 feet. --Use a deep pile and/or column foundation anywhere on a barrier island, if erosion/or scour are possible. --For sites near bay or sound shorelines, foundation selection should be based on several factors: erodibility of the soil; exposure to “damaging” waves (> 1.5 ft high); potential for velocity flow; potential for floodborne debris; and required resistance to lateral flood and wind forces. --Use pier foundations only where soil characteristics and flood conditions permit. If there are any doubts as to the appropriate foundation to use near bay and sound shorelines, elevate the building at least one story above grade on piles or another deeply embedded open foundation, and leave the area below free of obstructions or enclose it with breakaway walls. --Design foundations and structures to withstand loads from floodborne debris during a base flood event (100-year). --For barrier island sites outside the V Zone, the ground level floor of a multi-story building (typically used for vehicle parking and building access) should either: 1) use a lowest floor slab or floor system that will not collapse and can support all design loads, if undermined, or 2) use a slab or floor system that will collapse and break into small pieces if undermined. --Elevate heating, ventilation, and air conditioning equipment above the BFE, and preferably to the same elevation as the lowest floor of a building. The equipment should be supported to prevent damage from flooding and fastened to resist blow-off from high winds. The preferred approach is a cantilevered platform. --Ensure that breakaway walls are designed and built to break away cleanly and do not cause additional damage to the building. Minimize the size of any enclosure to the amount necessary for parking and building access. --Either elevate pools above the BFE on a pile foundation (and design the pool without side support from soil), or install a frangible (breakaway) pool at grade level and consider it expendable. Do not rely on a bulkhead to protect the pool during a severe storm. --Subject to local and state regulations for coastal armoring, assume that only heavy walls will provide protection during a severe storm, and note that even those may be overtopped by surge and waves. Consider lightweight bulkheads as temporary structures that may provide protection during minor storms, but which will likely fail during a major storm. Wind-related --Design and construct facilities to at least the minimum design requirements in the 2003 IBC in Alabama and the 2001 FBC and the 2004 FBC (after it becomes effective in the fall of 2005) in Florida. --When renovating or remodeling for structural or building envelope improvements (both residential and commercial), involve a structural engineer/design professional/licensed contractor in the design and planning. --Assure code compliance through increased enforcement of construction inspection requirements such as the Florida Threshold Inspection Law or the IBC Special Inspections Provisions. --Perform follow-up inspections after a hurricane to look for moisture that may affect the structure or building envelope. --Use the necessity of roof repairs to damaged buildings as an opportunity to significantly increase the future wind resistance of the structure. The following recommendations are specifically provided for state and Federal government agencies: --Re-evaluate the methodology to determine flood zones and flood elevations in coastal areas to address the inconsistencies between observed flood elevations (and damages) and BFEs (and anticipated damages). --Re-evaluate the storm surge data and modeling procedures that served as the basis for the effective FIRMs. --Use Hurricane Ivan tide levels, inundation limits, and areas subject to wave effects as proxies for reconstruction guidance until such time as new, up-to- date regulatory studies and maps can be prepared and adopted. --Allocate resources to hardening, providing backup power and data storage to NOAA/NWS’s surface weather monitoring systems, including the Automated Surface Observing System (ASOS) located in hurricane-prone regions. --Continue to fund the development of several different tools for estimating and mapping wind fields associated with hurricanes and for making these products available to the public as quickly as possible after a hurricane strikes. Additional recommendations and mitigation measures for design professionals, building officials, contractors, homeowners, and business owners are presented in Chapter 8, including: --Improving the performance of building structural and envelope systems through proper design of the continuous load path --Improving quality control and inspections --Retrofitting existing residential and commercial buildings from the roof decks to the foundations --Improving the performance of critical and essential facilities (including shelters) --Improving design and construction guidance --Improving public education and outreach [End of Executive Summary] Table of Contents Executive Summary i 1 Introduction 1-1 1.1 Hurricane Ivan – The Event 1-1 1.1.1 Storm Surge Analysis and Discussion 1-6 1.1.2 Wind Analysis and Discussion 1-22 1.2 Historical Hurricanes (Frequency of Hurricanes and Tropical Storms in Eastern Coastal Alabama and Florida Panhandle) 1-29 1.3 FEMA Mitigation Assessment Teams 1-31 1.3.1 Methodology 1-31 1.3.2 Team Composition 1-32 2 Floodplain Management Regulations and Building Codes and Standards 2-1 2.1 Floodplain Management Regulations 2-1 2.1.1 Flood Studies, Flood Maps, and Floodplain Management Regulations 2-3 2.1.2 Higher Regulatory Standards 2-5 2.1.3 Relating Observed Flood Damages to the FIRMs 2-5 2.1.3.1 Baldwin County, Alabama 2-6 2.1.3.2 Santa Rosa County, Florida 2-10 2.2 Building Codes and Standards 2-17 2.2.1 Flood Requirements in Building Codes and Standards-Alabama 2-17 2.2.1.1 Flood Provisions in the IBC (2003) 2-18 2.2.1.2 Flood Provisions in the IRC (2003) 2-18 2.2.1.3 Flood Requirements in ASCE 7 2-18 2.2.1.4 Flood Requirements in ASCE 24 2-18 2.2.1.5 Coastal Construction Control Line (Alabama) 2-19 2.2.2 Flood Requirements in Building Codes and Standards – Florida 2-20 2.2.2.1 Flood Provisions in the FBC (2004 Edition) 2-20 2.2.2.2 Coastal Construction Control Line (Florida) 2-20 2.2.3 Wind Requirements in Building Codes and Standards – Alabama 2-22 2.2.3.1 Comparing Design Wind Speeds 2-22 2.2.3.2 Comparing Design Wind Pressures 2-24 2.2.4 Wind Requirements in Building Codes and Standards – Florida 2-26 2.2.4.1 Comparing Design Wind Speeds 2-28 2.2.4.2 Comparing Calculated Wind Pressures 2-30 2.2.4.3 Comparing Debris Impact Requirements 2-32 2.2.4.4 High-Wind Elements of the Code 2-33 3 GENERAL CHARACTERIZATION OF DAMAGE 3-1 3.1 Flood Effects 3-1 3.1.1 Flood Effects on One- and Two-Family Housing 3-2 3.1.2 Flood Effects on Multi-Family Housing 3-9 3.2 Wind Effects 3-13 3.2.1 Summary of Damage Types 3-13 3.2.2 Wind Effects on One- and Two-Family Housing 3-15 3.2.3 Wind Effects on Multi-Family Housing 3-16 3.2.4 Wind Effects on Commercial Buildings 3-18 3.2.5 Wind Effects on Critical/Essential Facilities 3-19 3.3 Lessons Learned and Best Practices 3-20 4 STRUCTURAL SYSTEMS PERFORMANCE 4-1 4.1 Flood 4-1 4.1.1 Single-Family Residential Buildings 4-1 4.1.1.1 Pile Foundations 4-2 4.1.1.2 Slab on Grade 4-12 4.1.1.3 Stem Walls 4-15 4.1.1.4 Piers 4-17 4.1.2 Multi-Family Residential Buildings 4-21 4.1.2.1 Shallow Foundations 4-21 4.1.2.2 Pile Foundations 4-27 4.1.3 Miscellaneous Structures 4-32 4.1.3.1 Bulkheads 4-32 4.1.3.2 Non-Structural Slabs 4-35 4.1.3.3 Breakaway Walls 4-37 4.1.3.4 Utilities 4-39 4.1.3.5 Stairs 4-44 4.1.4 Debris Impacts 4-45 4.2 Wind 4-50 4.2.1 Wood Frames 4-50 4.2.2 Concrete Buildings 4-59 4.2.3 Commercial Buildings 4-59 4.2.4 Pre-Engineered Metal Buildings 4-60 4.2.5 Accessory Structures 4-62 5 BUILDING ENVELOPE PERFORMANCE 5-1 5.1 Sheathing on the Underside of Elevated Buildings 5-2 5.2 Doors 5-4 5.2.1 Personnel Door Damage 5-4 5.2.2 Garage Door Damage 5-6 5.2.3 Rolling and Sectional Door Damage 5-7 5.3 Non-Load-Bearing Walls, Wall Coverings, and Soffits 5-7 5.3.1 Non-Load-Bearing Walls 5-7 5.3.2 Wall Coverings and Soffits 5-23 5.4 Roof Systems 5-33 5.4.1 Asphalt Shingles 5-33 5.4.2 Tile 5-36 5.4.3 Metal Panel and Shingle Roofs 5-44 5.4.4 Low-slope Membrane Systems 5-46 5.5 Windows, Shutters, and Skylights 5-51 5.5.1 Unprotected Glazing 5-51 5.5.2 Protected Glazing 5-54 5.5.3 Skylights 5-56 5.6 Exterior Mechanical and Electrical Equipment Damage 5-57 5.6.1 Rooftop HVAC Equipment 5-58 5.6.2 Electrical and Communications Equipment 5-62 6 PERFORMANCE OF CRITICAL AND ESSENTIAL FACILITIES 6-1 6.1 Emergency Operation Centers 6-2 6.1.1 General Damage 6-2 6.1.2 Functional Loss 6-3 6.2 Hospitals 6-4 6.2.1 General Damage 6-4 6.2.2 Functional Loss 6-5 6.2.3 Best Practices - Hospitals 6-7 6.3 Schools 6-7 6.3.1 General Damage 6-8 6.3.2 Functional Loss 6-10 6.4 Shelters 6-10 6.4.1 General Damage 6-10 6.4.2 Functional Loss 6-11 7 CONCLUSIONS 7-1 7.1 Flood Hazard Conclusions 7-1 7.1.1 Lowest Floor Elevations 7-4 7.1.2 Foundations and Structures 7-6 7.1.3 Piers and Docks 7-6 7.1.4 Construction Features beneath Elevated Buildings 7-7 7.1.5 Pools and Bulkheads 7-8 7.1.6 Utilities 7-9 7.2 Wind Hazard Conclusions 7-10 7.2.1 Building Performance and Compliance with the Building Codes, Statutes, and Regulatory Requirements of the States of Alabama and Florida 7-12 7.2.2 Performance of Structural Systems (Residential and Commercial Construction) 7-15 7.2.2.1 Internal Pressures 7-15 7.2.2.2 Wind Mitigation for Existing Buildings 7-17 7.2.3 Performance of Building Envelope, Mechanical and Electrical Equipment 7- 18 7.2.4 The Need for High-Wind Design and Construction Guidance 7-27 7.2.5 Performance of Critical and Essential Facilities (Including Shelters) 7- 27 8 RECOMMENDATIONS 8-1 8.1 Flood Related Recommendations 8-1 8.1.1 General Hazard Identification Recommendations 8-1 8.1.2 Design Guidance 8-2 8.1.3 Foundation Recommendations 8-2 8.1.4 Building Utilities 8-6 8.1.5 Building Access Structures and Enclosures beneath Elevated Buildings 8- 7 8.1.6 Pools and Bulkheads 8-8 8.1.7 Public Outreach and Education 8-8 8.2 Wind Recommendations 8-14 8.2.1 Proposed Changes to Codes and Statutes 8-15 8.2.1.1 Statutory Building Code Provisions—Alabama 8-15 8.2.1.2 Statutory Building Code Provisions—Florida 8-16 8.2.1.3 Reference Standards—ASCE 7 8-17 8.2.2 Architectural, Mechanical, and Electrical 8-17 APPENDICES Appendix A References Appendix B Acknowledgments Appendix C Acronyms and Abbreviations Appendix D FEMA Recovery Advisories Appendix E Ivan Flood Recovery Maps Appendix F Orange Beach High-Rise Study TABLES Chapter 1 Table 1-1. Wind Speeds of the Saffir-Simpson Hurricane Scale 1-6 Table 1-2. Comparison of HWMs and BFEs for MAT Investigation Sites 1-8 Table 1-3. Estimated Maximum 3-Second Gust Wind Speeds at 10-Meters for MAT Investigation Sites (variations for terrain are provided) 1-23 Table 1-4. Notable Wind Speeds Recorded for Hurricane Ivan 1-28 Chapter 2 Table 2-1. Baldwin County Stillwater Elevations and BFEs (2002) 2-6 Table 2-2. Santa Rosa County Stillwater Elevations 2-11 Table 2-3. Basic Design 3-Second Gust Wind Speeds (For Baldwin and Mobile Counties, Alabama) 2-23 Table 2-4. Typical Single-Family Residence in Gulf Shores, Alabama 2-25 Table 2-5. Basic Design 3-Second Gust Wind Speeds (Ranges for Each County) 2- 29 Table 2-6. Wind Pressures on a Single-Family Residence in Pensacola, Florida 2-31 Chapter 7 Table 7-1. Design Wind Pressures Building Code 7-14 Chapter 8 Table 8-1. Recommended Foundations for Coastal Areas near Bay/Sound Shorelines and Not Mapped as V Zone 8-4 Table 8-2. Design and Construction Recommendations 8-10 Table 8-3. Hazard Identification and Regulations Recommendations 8-11 Table 8-4. Public Outreach Recommendations 8-12 Table 8-5. Recommendations Specific to Critical and Essential Facilities 8- 14 Table 8-6. Design and Construction Recommendations 8-19 Table 8-7. Building Code Recommendations 8-22 Table 8-8. Public Outreach Recommendations 8-25 Table 8-9. Recommendations Specific to Critical and Essential Facilities 8- 27 Appendix F Table F-1. Summary of Orange Beach, Alabama, High-Rise Buildings Inspected F- 2 Table F-2. Description of Damage States Used in the Orange Beach High-Rise Study F-6 Table F-3. Orange Beach High-Rise Buildings (n = 41) Classified by Lowest Floor Living Unit Damage States F-7 Table F-4. Numbers of Lowest Floor Living Units Classified by Damage States (n = 233) for 41 Orange Beach High-Rise Buildings F-8 Table F-5. Damage States versus Top of Lowest Floor Elevation F-10 Table F-6. Damage States versus Average Erosion Depth F-12 FIGURES Chapter 1 Figure 1-1. Path of Hurricane Ivan 1-4 Figure 1-2. Surge elevation contours in Baldwin County, Alabama 1-10 Figure 1-3. Surge elevation contours in Escambia County, Florida 1-10 Figure 1-4. Surge elevation contours in Santa Rosa County, Florida 1- 11 Figure 1-5. Surge elevation contours in Okaloosa County, Florida 1-12 Figure 1-6. The SLOSH model Envelope of High Water (EOHW) for Pensacola Bay, Florida 1-13 Figure 1-7. CHWM surveyed elevations for Dauphin Island area 1-14 Figure 1-8. CHWM surveyed elevations for Upper Mobile Bay area 1-14 Figure 1-9. CHWM surveyed elevations for West Beach/Fort Morgan area 1- 15 Figure 1-10. CHWM surveyed elevations for Orange Beach/Ono Island 1-16 Figure 1-11. CHWM surveyed elevations for Innerarity Point and Perdido Key areas 1-17 Figure 1-12. CHWM surveyed elevations for Pensacola/Gulf Breeze area 1- 18 Figure 1-13. CHWM surveyed elevations for Upper Escambia Bay area 1-18 Figure 1-14. CHWM surveyed elevations for Blackwater Bay area 1-19 Figure 1-15. CHWM surveyed elevations for Holley Navarre area 1-19 Figure 1-16. CHWM surveyed elevations for Fort Walton area 1-20 Figure 1-17. CHWM surveyed elevations for Destin area 1-21 Figure 1-18. Extent of hurricane and tropical storm force winds for Hurricane Ivan 1-24 Figure 1-19. Maximum recorded wind speeds from Hurricane Ivan normalized to 3-second peak gust at 10 meters, Exposure C 1-25 Figure 1-20. Wind swath contour plot (1-minute sustained winds at 10 meter elevation) based on H*wind analysis 1-26 Figure 1-21. Wind swath contour plot (3-second gust at 10-meter elevation) based on HAZUS-MH wind field methodology (ARA) 1-27 Figure 1-22. Historical hurricane and tropical storm paths 1-30 Figure 1-23. Some of the locations visited by the MAT 1-32 Chapter 2 Figure 2-1. Floodplain Management Regulations and Building Design, Alabama 2-2 Figure 2-2. Floodplain Management Regulations and Building Design, Florida 2-3 Figure 2-3. Baldwin County location near the State Park/Orange Beach boundary where the historical FIRMs were reviewed. 2-7 Figure 2-4. Comparison of FIRMs over time, at the State Park boundary, west end of Orange Beach (Orange Beach, Baldwin County, Alabama) 2-8 Figure 2-5. Ivan damage at the west boundary of Orange Beach. Houses are missing from piles and piles are broken near the ground level. (Orange Beach/State Park boundary) 2-9 Figure 2-6. Ground photo of the same area as Figure 2-5. At this location, all houses seaward of the blue house (circled) were destroyed. 2-9 Figure 2-7. Building on the right side of Figure 2-5 survived, although it sustained destruction of the lower enclosed area and suffered extensive internal damage due to wind. 2-10 Figure 2-8. Santa Rosa County locations where historical FIRMs were reviewed 2-11 Figure 2-9. Santa Rosa County: Comparison of FIRMs at the centerline of the intersection of Bay Street and Harrison Avenue 2-12 Figure 2-10. Typical houses at Birdseye Circle, which had 2 to 4 feet of flooding inside the houses. 2-13 Figure 2-11. Typical damage to houses along Bay Street that were impacted by surge and wave effects from Santa Rosa Sound. (Santa Rosa County) 2-13 Figure 2-12. Aerial view of houses along Bay Street and Santa Rosa Sound that were heavily damaged by storm surge and wave impacts. 2-14 Figure 2-13. The house in the foreground was constructed on piles and had minimal flood damage during Ivan, although it lost a pile support for the deck. 2-15 Figure 2-14. The house on the right (circled), which is at the west end of Del Mar Drive, south of Bay Street, along the Santa Rosa Sound, was heavily damaged by storm surge and wave and debris impacts. 2-15 Figure 2-15. This house, located on Santa Rosa Sound and circled in Figure 2-14, was severely damaged by surge, wave, and debris impacts. 2- 16 Figure 2-16. Design Wind Speeds from IBC 2003 and ASCE 7-98 and 02 2-23 Figure 2-17. Wind speed and windborne debris region map (Courtesy of the Florida Building Commission, 2001) 2-29 Chapter 3 Figure 3-1. Buildings constructed on deep pile foundations performed well; however, significant damage occurred to lower-level enclosed areas and to stairways, utilities, and non-structural parking slabs below the elevated portion of the building. 3-3 Figure 3-2. Insufficient pile embedment caused displacement of houses (Gulf Shores, West Beach) 3-3 Figure 3-3. This building, which was less than 2 years old, was constructed on piers at the current BFE of 9 feet. It was severely damaged by high storm surge, and wave and debris impacts. (Big Lagoon) 3-4 Figure 3-4. Damage to NFIP-compliant elevated structure in a V Zone (north end of Escambia Bay-Floridatown) 3-5 Figure 3-5. Buildings constructed on piles and elevated several feet above the BFE sustained less flood damage than adjacent buildings at lower elevations. (Big Lagoon) 3-5 Figure 3-6. Surge, wave, and debris damage (Little Lagoon) 3-6 Figure 3-7. Older buildings below the current BFE sustained severe flood damage throughout the back bays. (Little Lagoon) 3-6 Figure 3-8. This new building was constructed to the BFE, but was wiped off its foundation (slab atop stem walls) by Ivan. (Big Lagoon) 3-7 Figure 3-9. Utilities, parking slabs, and enclosed areas under an elevated building were severely damaged by the high flood elevations and wave action. (Gulf Shores) 3-7 Figure 3-10. Large timbers washed from developments on Santa Rosa Island, across Santa Rosa Sound, and into several homes (Santa Rosa Sound – Oriole Beach) 3-8 Figure 3-11. Significant floodborne debris contributed to the severe damage of at-grade enclosed area beneath an elevated building. (Big Lagoon) 3-8 Figure 3-12. Significant floodborne debris contributed to the severe damage of buildings throughout the back bays and sounds in areas mapped as Zone AE. (Oriole Beach – Santa Rosa Sound) 3-9 Figure 3-13. Collapse of 5-story, multi-family buildings on shallow foundations (Orange Beach) 3-10 Figure 3-14. Pile foundations performed well, but non-structural floor slabs collapsed and low-elevation living units were destroyed.(Orange Beach) 3-10 Figure 3-15. Building supported on pile foundation (foreground) survived while building on shallow foundation (background) collapsed. (Orange Beach) 3- 11 Figure 3-16. Foundation and structural floor slab survived but lowest floor non-structural exterior walls were destroyed by surge and waves (Orange Beach) 3-12 Figure 3-17. Destruction of low-elevation living units by surge and waves, while second floor units survived intact (Orange Beach) 3-12 Figure 3-18. Typical wind damage showing loss of roof sheathing and damage to structural roof framing (Ono Island) 3-16 Figure 3-19. Typical roof sheathing and covering loss (Pensacola Beach) 3- 16 Figure 3-20. Typical gable end wall failure and loss of roof sheathing and wall (Perdido Key) 3-17 Figure 3-21. Typical high rise cladding failure (Perdido Key) 3-17 Figure 3-22. Commercial building roof covering failure (Pensacola Beach) 3- 18 Figure 3-23. Commercial building wall cladding and secondary structure failure (Gulf Shores) 3-18 Figure 3-24. Pre-engineered metal building damage (Orange Beach) 3-19 Figure 3-25. Metal wall panel damage to middle school (Gulf Breeze) 3- 19 Figure 3-26. Roof covering and roof deck damage to middle school (Pensacola) 3-20 Figure 3-27. After this building was destroyed by Hurricane Frederic in 1979 (upper photo), it was re-constructed on concrete columns, pile caps, and deep piles. (Gulf Shores) 3-21 Figure 3-28. Severe corrosion of reinforcing steel and spalling of the concrete columns supporting the post-Frederic building shown in Figure 3- 27. 3-22 Figure 3-29. Hurricane Opal (1995) flood damage to one of the four original buildings 3-23 Figure 3-30. 1998 photograph showing the post-Opal replacement (pile supported) building (background) and one of the three remaining older buildings (foreground) 3-23 Figure 3-31. Post-Ivan aerial photograph showing severe flood damage to two of the three older buildings, with newer, pile-supported building intact (left side) 3-24 Figure 3-32. Ivan flood and wind damage to older building (post-Opal building visible at far left) 3-24 Figure 3-33. Hurricane Ivan, non-structural enclosure and deck damage below newer building 3-25 Figure 3-34. Four Orange Beach condominiums before Hurricane Ivan. The lower pair of buildings was newer, having been constructed after the predecessors were destroyed by Hurricane Georges (1998). (USGS) 3-26 Figure 3-35. The four condominiums in Figure 3-34 after Hurricane Ivan (USGS) 3-27 Figure 3-36. Deep foundation exposed by erosion, and collapse of undermined parking slab, as shown in the photo on the right. 3-28 Figure 3-37. Elevated building constructed to newer code that survived Hurricane Ivan (Big Lagoon) 3-29 Figure 3-38. Older, non-elevated building (near building in Figure 3-37) severely damaged in Hurricane Ivan (Big Lagoon) 3-29 Figure 3-39. House on La Paz Street that was not elevated to the current BFEs, and, therefore, was severely damaged by the high coastal flooding and wave impacts. 3-30 Figure 3-40. House on La Paz Street that was elevated on piles, which prevented severe damage from coastal flooding. 3-30 Figure 3-41. House on La Paz that was elevated on piles, which prevented major flood damage 3-31 Figure 3-42. The surviving house was built to incorporate the provisions of the new building code (IRC, IBC) even before it was adopted. (Orange Beach) 3-31 Chapter 4 Figure 4-1. House on a pile foundation that performed well. It experienced 5 feet of erosion that resulted in failure of a non-structural slab.(Gulf Shores) 4-3 Figure 4-2. House on pile foundation, adjacent to breach in the barrier island, that experienced erosion and significant non-structural damage below the lowest floor (Gulf Shores). 4-3 Figure 4-3. These pile-elevated houses in an area mapped as Zone VE at Pensacola Beach successfully resisted flood forces. Loss of breakaway enclosures and garage doors below the lowest floors occurred. (FL DEP Photo). 4-4 Figure 4-4. Row of newer houses on pile foundations that experienced significant damages below the lowest floor, but overall the pile foundation systems performed well. (Gulf Shores) 4-4 Figure 4-5. Floor joists were pushed landward when the wave crest elevation was above the floor beam. (Gulf Shores). 4-5 Figure 4-6. Significant erosion caused the non-structural parking slab to fail, and insufficient pile embedment caused the structure to lean. (Orange Beach) 4-5 Figure 4-7. Erosion contributed to loss of the porch, failure of the retaining wall and non-structural parking slab, and destruction of the enclosure below the first floor. (Orange Beach) 4-6 Figure 4-8. The pile foundations in the foreground failed. These houses were washed away (see Figures 3-2 and 4-9). 4-6 Figure 4-9. These houses floated off their pile foundations (shown in Figures 4-8 and 3-2). 4-7 Figure 4-10. House constructed on a pile foundation in a V Zone along Escambia Bay (Floridatown) 4-8 Figure 4-11. Damage to pile-supported house on a bay shoreline, when flooding and waves exceeded the lowest floor elevation (Gulf Breeze, Pensacola Bay) 4-8 Figure 4-12. House at left (circle) was torn from its pile foundation. New houses under construction survived Ivan (Big Lagoon). 4-9 Figure 4-13. Same destroyed house as in Figure 4-12 (circled). Note adjacent pile-elevated houses near shoreline, also destroyed (Big Lagoon). 4-9 Figure 4-14. House constructed on piles several feet higher than the BFE. Floodwater, waves, and debris caused damages to the ground level enclosed area of the house, but not to the elevated portion. (Big Lagoon) 4- 10 Figure 4-15. Area just to the west of the house shown in Figure 4-14. Pile-elevated houses above the BFE (circled) survived, while older houses on slab foundations were destroyed. 4-11 Figure 4-16. Ground view of some of the debris shown in Figure 4-15. 4- 11 Figure 4-17. This house located near Sinton Drive successfully resisted flood forces since it was elevated higher than the BFE on piles. (Big Lagoon) 4-12 Figure 4-18. This photo shows the destroyed building adjacent to the house in Figure 4-17. (Big Lagoon) 4-12 Figure 4-19. The pre-FIRM building constructed on a slab foundation (foreground) was completely destroyed. (Big Lagoon) 4-13 Figure 4-20. Destruction of slab-on-grade house (circled) in the Grande Lagoon neighborhood (Big Lagoon) 4-13 Figure 4-21. The unreinforced masonry pre-FIRM building in the foreground was swept off its slab foundation during Ivan. (Oriole Beach) 4-14 Figure 4-22. This slab-on-grade building located on the back side of the barrier island but directly on the sound was heavily damaged by wave action. (Pensacola Beach) 4-14 Figure 4-23. The slab-on-grade building located near the back side of the barrier island was protected from wave action by other houses, but had 4 to 5 feet of water inside. (Pensacola Beach) 4-15 Figure 4-24. House constructed in a Zone AE on a stem wall foundation, which survived, although high floodwaters with debris and wave action caused major damage (Big Lagoon) 4-16 Figure 4-25. Stem wall foundation where floodwater exceeded required flood elevation by approximately 4 feet (Garcon Point, Escambia Bay) 4- 16 Figure 4-26. This stem foundation elevated the house above the BFE and performed well. (Tiger Point, Santa Rosa Sound) 4-17 Figure 4-27. Unreinforced pier foundations failed due to scour at the footing and flood levels exceeding the floor elevation Oriole Beach). . 4- 18 Figure 4-28. Center pier failed causing the elevated floor to collapse. (Santa Rosa Sound) 4-18 Figure 4-29. Tall, lightly reinforced masonry piers failed due to lateral loads from surge and wave action. (Big Lagoon). 4-19 Figure 4-30. Manufactured home park where houses experienced storm surge, scour, and foundation collapse (Orange Beach) 4-19 Figure 4-31. Unreinforced, dry-stacked block piers slid off of footings. (Orange Beach) 4-20 Figure 4-32. Dry-stacked pier failure (Orange Beach) 4-20 Figure 4-33. Total collapse of 5-story building on a shallow foundation (Orange Beach) 4-22 Figure 4-34. Close-up of building shown in Figure 4-33 (Orange Beach) 4- 22 Figure 4-35. Shallow foundation failure (Orange Beach - Perdido Key) 4- 23 Figure 4-36. Collapse of a 5-story building constructed on a shallow foundation (Orange Beach) Photo courtesy of USGS 4-24 Figure 4-37. Collapse of the seaward portion of a high-rise building supported by a shallow foundation (Perdido Key) 4-25 Figure 4-38. Older buildings constructed on masonry columns and walls atop shallow footings (Pensacola Beach). 4-25 Figure 4-39. This building has been flooded by Hurricane Ivan and four prior storms. (Pensacola Beach) 4-26 Figure 4-40. Multi-family building on a bay shoreline, heavily damaged by surge, waves and floating debris (Oriole Beach, Santa Rosa Sound) 4-27 Figure 4-41. Aerial view of building in Figure 4-40 4-27 Figure 4-42. Multi-story buildings on piles, impacted by storm surge, waves, and erosion, which damaged many lower area walls and floors (Orange Beach) 4-28 Figure 4-43. Although the pile foundation and structural elements survived, damage to lowest floor exterior walls, interior partitions, and floor slabs occurred during Ivan. (Orange Beach) 4-28 Figure 4-44. The building on the left shows minimal damage, while the building on the right with the lower-level living units experienced significant non-structural damage. (Orange Beach) 4-29 Figure 4-45. This condominium on a deep foundation is located on the back side of the barrier island, north of Ft. Pickens Road. (Pensacola Beach) 4- 30 Figure 4-46. Aerial view of the building shown in Figure 4-45 (FL DEP photo) (Pensacola Beach) 4-30 Figure 4-47. Building with flood and wave damage to the lowest floor living units (Perdido Key) 4-31 Figure 4-48. Most of the first floor units in these buildings were severely damaged (see Figures 4-53 and 4-54). (Orange Beach) 4-31 Figure 4-49. Pile support buildings performed much better than buildings constructed on shallow foundations. (Orange Beach) 4-32 Figure 4-50. Typical pool failure (Pensacola Beach) 4-33 Figure 4-51. Retaining wall failure (Gulf Shores) 4-33 Figure 4-52. Failure of vinyl bulkhead with concrete cap (Orange Beach) 4- 34 Figure 4-53. Bulkhead remained intact, but short return wall allowed erosion behind the wall (Orange Beach). 4-34 Figure 4-54. Bulkhead shown in Figure 4-53 remained in-place, but surge and wave overtopping, coupled with erosion at the short return wall, led to deck and retaining wall failure. (Orange Beach) 4-35 Figure 4-55. Sand below slab completely eroded away, causing the total failure of slab, but grade beams remained intact. (Gulf Shores) 4-35 Figure 4-56. Concrete slab partially separated from the pile even though it had been connected with a nail. (Gulf Shores) 4-36 Figure 4-57. Typical non-structural concrete slab failure. Horizontal line indicates previous location of soil level and slab. (Orange Beach) 4- 36 Figure 4-58. This slab failed but did not break into small pieces due to the reinforcing steel. (Orange Beach) 4-37 Figure 4-59. Failure of breakaway walls as designed (Gulf Shores) 4-38 Figure 4-60. Poor detailing of the joint between the breakaway wall and the wall above contributed to loss of wall covering above the floor beam. (Pensacola Beach). 4-38 Figure 4-61. Failure of interior partition to break away cleanly due to the attachment of utilities (Gulf Shores) 4-39 Figure 4-62. Breakaway walls were nailed over the piles and floor beam, preventing a clean break. (Gulf Shores) 4-39 Figure 4-63. Loss of condenser platform support. A cantilevered condenser support is recommended. (Pensacola Beach) 4-40 Figure 4-64. Diagonal condenser platform members are susceptible to wave and waterborne debris damage. (Gulf Shores) 4-40 Figure 4-65. Elevator system severely damaged by surge, waves, and debris (Gulf Shores) 4-41 Figure 4-66. Loss of platform supports and air conditioning unit due to erosion and flood forces (Gulf Shores) 4-41 Figure 4-67. House under construction at the time of Ivan (Big Lagoon) 4- 42 Figure 4-68. Erosion and flood damage to multi-family electrical transformer and interior mechanical room (Perdido Key) 4-42 Figure 4-69. Debris and sand in low-elevation mechanical room (Perdido Key) 4-43 Figure 4-70. Damage to the electrical panel, but utility lines were located appropriately (beside an interior pile) (Pensacola Beach) 4-43 Figure 4-71. Drain lines constructed between interior piles (which helped to protect them from flood forces), although electrical box was connected to plywood panel and was destroyed (Pensacola Beach) 4-44 Figure 4-72. Massive stairs that will obstruct flows could deflect waves and debris into the elevated building. (Gulf Shores) 4-45 Figure 4-73. Stairway structures (circled) that will minimize obstructions to flow and potential adverse effects on the elevated building (Gulf Shores) 4-45 Figure 4-74. Large accumulation of debris trapped between house and dune walkover (Gulf Shores) 4-46 Figure 4-75. Ground level photograph of debris shown in Figure 4-74 (Gulf Shores) 4-46 Figure 4-76. Marine pile debris washed into this house in the back bay. (Oriole Beach) 4-47 Figure 4-77. Same marine pile as shown in Figure 4-76. (Oriole Beach) 4-47 Figure 4-78. Boats and dock debris from a marina struck this pile-elevated building, deforming floor beams, breaking joist connections, and scarring pilings. (Big Lagoon) 4-48 Figure 4-79. Typical view of destroyed docks contributing to floodborne debris (Big Lagoon) 4-48 Figure 4-80. Small stones from a nearby revetment were likely propelled by waves into this north-facing sound side house, breaking windows and sliding glass doors. (Gulf Breeze) 4-49 Figure 4-81. The small stone revetment contributed stones which were propelled by waves and struck the house shown in Figure 4-80 (Gulf Breeze) 4-49 Figure 4-82. Load path of a two-story building with a primary wood-framing system: walls, roof diaphragm, and a floor diaphragm 4-51 Figure 4-83. Storm surge damaged the lower portion of this house, but no wind damage was observed. (Gulf Shores) 4-52 Figure 4-84. Progressive failure of wood roof framing (Perdido Key) 4- 53 Figure 4-85. Gable end wall framing diagram 4-54 Figure 4-86. Roof truss with 2x4s oriented in the weak direction resisting the wind loads on a gable end wall (Ono Island) 4-54 Figure 4-87. Gable end wall failure due to lack of bracing at hinge point in wall (see arrow) (Perdido Key) 4-55 Figure 4-88. Roof framing damage due to lack of connections from roof to wall (Orange Beach) 4-56 Figure 4-89. Roof framing damage due to lack of connections from roof to wall (Pensacola Beach) 4-56 Figure 4-90. Roof framing damage due to lack of connections from roof to wall (Ono Island) 4-57 Figure 4-91. Improper use of a wood truss press plate connector to substitute for stud hold-downs (Oriole Beach) 4-57 Figure 4-92. Already corroded anchor bolt in new construction (Oriole Beach) 4-58 Figure 4-93. Improper strapping (Ono Island) 4-58 Figure 4-94. Wall studs between garage doors with inadequate hold-downs (Ono Island) 4-59 Figure 4-95. Metal roofing failure (Foley) 4-60 Figure 4-96. Heavily damaged pre-engineered boat storage building (Orange Beach) 4-61 Figure 4-97. Heavily damaged pre-engineered boat storage building (Orange Beach) 4-61 Figure 4-98. Collapsed metal canopy at a middle school (Pensacola) 4-62 Chapter 5 Figure 5-1. Loss of vinyl siding panels from the underside of an elevated residence in Gulf Shores (Laguna Key) 5-2 Figure 5-2. Loss of gypsum board from the underside of an elevated residence in Gulf Shores (Laguna Key) 5-3 Figure 5-3. Loss of plywood from the underside of an elevated residence in Gulf Shores (West Beach) 5-3 Figure 5-4. Tempered glass door broken by debris from a mortar-set tile roof (Pensacola) 5-5 Figure 5-5. Sliding glass door frame blown from the wall 5-5 Figure 5-6. Floodwater collapsed the garage door at the left end of this residence. (Laguna Key) 5-6 Figure 5-7. Typical EIFS assembly 5-8 Figure 5-8. Typical stucco assembly 5-9 Figure 5-9. Vertical peeling on a home in Gulf Shores due to lack of a projecting band or reveal after the breakaway wall failed (Laguna Key) 5-10 Figure 5-10. All gypsum board blown off and two windows broken by debris. Note the missing studs. (Pensacola Beach) 5-11 Figure 5-11. Severely deteriorated studs and corroded metal connectors 5- 11 Figure 5-12. Blown off EIFS revealed severely rotted oriented strand board (OSB) due to water infiltration at windows and wall penetration. 5-12 Figure 5-13. Loss of EIFS on a commercial building 5-13 Figure 5-14. Multi-story building showing severe EIFS damage. The gypsum board typically detached from the studs. 5-13 Figure 5-15. The gypsum board detached from the studs at the penthouse. Rainwater infiltration damaged the elevator controls. (Pensacola) 5-14 Figure 5-16. EIFS blew off the hospital building in the background (see red circle and Figures 5-18 and 6-2). (Pensacola) 5-15 Figure 5-17. Looking down at the one-story roof to the right of the MOB in Figure 5-16 5-15 Figure 5-18. Close up of the damaged EIFS at the hospital 5-16 Figure 5-19. Wood studs and gypsum board had been temporarily installed after the hurricane. 5-17 Figure 5-20. Hospital with EIFS blown off a cast-in-place wall. Note the damaged rooftop ductwork. (Pensacola) 5-17 Figure 5-21. Close-up of Figure 5-20. The light colored round marks indicate where adhesive had been applied. (Perdido Key) 5-18 Figure 5-22. Failure of non-load-bearing stucco wall (see close-up of Figure 3-21) 5-20 Figure 5-23. Close-up of Figure 3-21. With complete loss of the walls, the residents could have inadvertently fallen from the building. 5-21 Figure 5-24. Six-year old, stucco-sheathed residence with severely rotted plywood (Pensacola Beach) 5-22 Figure 5-25. At the end wall of the center building, stucco blew off the concrete substrate. 5-22 Figure 5-26. Brick veneer failure on an office building (Pensacola). 5- 24 Figure 5-27. Wood-frame residence has several corrugated ties that were never embedded into the mortar joints (see inset) 5-25 Figure 5-28. These panels were attached with concealed fasteners. They unlatched at the standing seams. 5-26 Figure 5-29. The green fascia panels had been installed over a previous metal panel system. 5-27 Figure 5-30. Loss of vinyl soffits was common. 5-28 Figure 5-31. Although a high-wind panel was used, extensive loss of siding and housewrap underlayment occurred. See Figure 5-32. 5-29 Figure 5-32. A double thickness of vinyl occurred at the nailing flange. However, many of the panels pulled over the nail heads. 5-29 Figure 5-33. When a panel becomes unlatched, it becomes very susceptible to blow-off. 5-30 Figure 5-34. Failure of wood framed exterior walls covered with the wood siding 5-32 Figure 5-35. Vinyl siding had been installed over textured plywood siding. 5-32 Figure 5-36. The vertical lines of missing shingle tabs are indicative of installation via the raking method. 5-34 Figure 5-37. Partial blow-off of ridge vent. When the plywood was slotted, the trusses and truss plates were cut. 5-35 Figure 5-38. Missing tabs 5-35 Figure 5-39. This roof is indicative of tile failure at modest wind speeds, wherein failure of eave, hip, and rake tiles were most common. 5-36 Figure 5-40. Direct-to-deck mechanically attached clay tile 5-37 Figure 5-41. Both nails were located in the right corner. 5-38 Figure 5-42. The fastener heads on this direct-to-deck mechanically attached tile roof had corroded. 5-38 Figure 5-43. Loss of several batten-attached tiles from a mid-rise building 5-39 Figure 5-44. Although some of these batten-attached tiles were damaged by wind pressure, the majority were damaged by windborne debris. 5-40 Figure 5-45. The majority of these batten-attached tiles were displaced by wind pressure. 5-40 Figure 5-46. The majority of these batten-attached tiles were displaced by wind pressure. 5-41 Figure 5-47. The tiles on the lower sloped roof were foam-set. The damage on this roof was due to a combination of wind pressure and windborne debris. 5- 41 Figure 5-48. These tiles were foam-set. See Figures 5-49 and 5-50. 5-42 Figure 5-49. A minuscule amount of foam was installed. Note that one tile slid down-slope about 2" (red arrow). See Figure 5-50. 5-42 Figure 5-50. View of the underside of the tile that slid in Figure 5-49. 5- 43 Figure 5-51. Significant loss of hip and ridge tiles 5-43 Figure 5-52. These hip and ridge tiles were foam-set. 5-44 Figure 5-53. Loss of standing seam metal panels. See Figure 5-54. (Pensacola) 5-44 Figure 5-54. These panels nearly blew away. The seams on three of the panels opened up. (Pensacola) 5-45 Figure 5-55. This 5-V crimp metal panel roof performed very well. 5-45 Figure 5-56. This residence had metal shingles that simulated the appearance of tile. 5-46 Figure 5-57. Although the metal edge flashing lifted, a progressive membrane lifting and peeling did not occur. (Pensacola) 5-47 Figure 5-58. The edge nailer on top of an old brick wall was inadequately attached to the wall. (Pensacola) 5-48 Figure 5-59. Loss of a mineral-surfaced BUR installed over LWIC. (Pensacola) 5-49 Figure 5-60. Minor base flashing displacement on a new hospital roof (Gulf Breeze) 5-49 Figure 5-61. Single-ply membrane torn by windborne debris (Pensacola) 5- 50 Figure 5-62. This hospital roof had been punctured in several locations by windborne debris. (Pensacola) 5-50 Figure 5-63. Several windows on this ocean-front home were broken by windborne debris. 5-53 Figure 5-64. The outer pane of this tempered glass window was broken by windborne debris. (Pensacola) 5-53 Figure 5-65. This shutter was impacted by high-energy debris. 5-54 Figure 5-66. Shutters had been retrofitted on this school, but the glazing above and below the window air conditioners and the glass entry doors were not protected. (Pensacola) 5-55 Figure 5-67. These panels did not completely cover the glazing. 5-55 Figure 5-68. It was unclear whether some panels blew away, or the glazing was not fully protected. 5-56 Figure 5-69. Several laminated glass panes were broken, but they remained in their frames. (Pensacola) 5-57 Figure 5-70. Loss of two fan cowlings on an EOC (Pensacola) 5-58 Figure 5-71. Loss of the hood at this relief air vent allowed rainwater to directly enter the school. (Pensacola) 5-59 Figure 5-72. At this hospital, the condenser moved off the sleepers and a nearby relief air hood was blown away. (Pensacola) 5-59 Figure 5-73. This large HVAC unit blew off a new medical office building. (Gulf Breeze) 5-60 Figure 5-74. Sheet metal access panels and shrouds were blown off this equipment at a hospital. (Pensacola) 5-61 Figure 5-75. Ductwork and fan units on this hospital were damaged in several locations. (Pensacola) 5-61 Figure 5-76. Damaged ductwork at a hospital (Pensacola) 5-62 Figure 5-77. Damaged ductwork at an EOC (Pensacola) 5-62 Figure 5-78. The LPS on this hospital became detached. (Pensacola) 5-63 Figure 5-79. The LPS conductor on this hangar became detached and punctured the roof membrane in several locations. (Pensacola) 5-63 Figure 5-80. The antennas at this hospital were damaged when the roof membrane blew off. (Pensacola) 5-64 Figure 5-81. The antenna at this hospital collapsed. (Pensacola) 5-64 Figure 5-82. Collapsed light fixtures at a hospital (Pensacola) 5-65 Chapter 6 Figure 6-1. General view of the roof membrane and rooftop equipment damage at the Escambia County Sheriff’s Office/EOC. (Pensacola) 6-3 Figure 6-2. View of EIFS damage at hospital building (Pensacola) 6-4 Figure 6-3. General view of upper roof of the Pensacola Naval Hospital (Pensacola) 6-5 Figure 6-4. View of a portion of the lowest floor roof showing broken 2nd and 3rd floor windows and debris from the roof above shown in Figure 6-3 6- 6 Figure 6-5. Walkway canopy collapse at Bellview Middle School (Pensacola) 6-8 Figure 6-6. Loss of cementitious wood-fiber roof deck panels at Workman Middle School (Pensacola) 6-9 Figure 6-7. Loss of the roof structure and rear portion of the CMU load-bearing wall at the George Stone Career Center auto shop (Pensacola) 6-9 Figure 6-8. Loss of asphalt shingles and underlayment at the Jim C. Bailey Middle School (Pensacola) 6-12 Chapter 7 Figure 7-1. Newly constructed house in Zone AE, which was damaged due to high flood levels and impacts from waves and floodborne debris. (Big Lagoon) 7- 3 Figure 7-2. Barrier island on Santa Rosa Island, east of Pensacola Beach, which was completely overwashed by storm surge. 7-3 Figure 7-3. Lowest floor elevation was one of the most important factors in determining building damage during Ivan (Gulf Shores, Little Lagoon) 7-5 Figure 7-4. Docks along back bays contributed to flood debris causing extensive damage. 7-7 Figure 7-5. Access stairs and enclosures that were constructed below the lowest floor were severely damaged. 7-8 Figure 7-6. Typical failure of swimming pools and bulkheads (Gulf Shores) 7-9 Figure 7-7. Inappropriately mounted condensers for a coastal residential site 7-10 Figure 7-8. Window damage caused exterior wall failure (Gulf Shores) 7- 16 Figure 7-9. Partition walls destroyed by interior pressurization due to window damage (Gulf Shores) 7-17 Figure 7-10. Although this was a structural success, this building was an envelope failure. . 7-20 Figure 7-11. In this EIFS failure, the majority of the gypsum board detached from the studs. 7-21 Figure 7-12. Rather than cutting off the tabs, the starter course on this new roof was turned 180 degrees. 7-22 Figure 7-13. These batten-attached tiles were damaged by windborne debris. 7-23 Figure 7-14. Glazing at the top two window units broken by debris, while the entire middle window unit was blown away. 7-25 Figure 7-15. A few of the upper level windows were broken. 7-26 Figure 7-16. An older hospital that experienced blown off roof coverings, gutters, downspouts, rooftop equipment, and broken glazing 7-28 Figure 7-17. Rooftop mechanical equipment damage at a hospital 7-29 Chapter 8 Figure 8-1. Freeboard and open foundations are recommended for V Zones and coastal A Zones. 8-3 Figure 8-2. Recommended design details for masonry piers where this foundation type is appropriate 8-5 Figure 8-3. A cantilevered platform. 8-7 Appendix E Figure E-1. Sample Flood Recovery Map A9 for Gulf Shores, Alabama. E-2 Appendix F Figure F-1. Sample data sheet for Orange Beach high-rise study F-3 Figure F-2. Locations of 43 high-rise buildings inspected in Orange Beach, Alabama (numbers are code numbers assigned during inspections) F-4 Figure F-3. Top of lowest floor elevations for Orange Beach high-rise buildings F-5 Figure F-4. Lowest floor living unit elevations F-5 Figure F-5. Floor intact, wall intact damage state F-8 Figure F-6. Floor intact, wall destroyed damage state F-9 Figure F-7. Floor destroyed, wall destroyed damage state F-9 Figure F-8. Floor intact, wall intact damage state versus top of lowest floor elevation F-11 Figure F-9. Floor destroyed, wall destroyed damage state versus top of lowest floor elevation F-11 [End of Table of Contents]