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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness Summary The Interagency Performance Evaluation Task Force (IPET) was established in October, 2005 by the U.S. Army Corps of Engineers to evaluate the performance of the New Orleans hurricane protection system during Hurricane Katrina. In December, 2005 the National Academy of Engineering/National Research Council (NAE/NRC) Committee on the New Orleans Hurricane Protection Projects was established to provide independent, expert advice to the IPET by reviewing a series of IPET draft reports. This is the NAE/NRC committee’s fifth and final report. It provides the committee’s assessment of the IPET draft final report that was issued in June, 2008. It also summarizes the committee’s views on key lessons learned from the Katrina experience and their implications for future hurricane preparedness and planning for south Louisiana (the committee’s full statement of task is listed in Appendix A). REVIEW OF THE IPET DRAFT FINAL REPORT IPET Study Objectives and Key Contributions The IPET conducted its evaluations in five areas: design and status of the hurricane protection system pre-Katrina; storm surges and waves generated by Hurricane Katrina; performance of the hurricane protection system during and after the storm; societal-related consequences of Katrina-related damage; and, risks to New Orleans and the region posed by future tropical storms. The IPET studies and draft final report represented important advances in characterizing and understanding the nature of Gulf hurricanes, and the storm surge response along the northern Gulf coast and the greater New Orleans area hurricane protection system. The IPET studies also have made significant contributions to simulating hurricane impacts and characterizing the collective effects of hurricane damage. The modeling procedures developed by IPET to help visualize and manage risk in communities impacted by Hurricane Katrina
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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness have improved knowledge of regional vulnerability to hurricanes and storm surge. This NAE/NRC committee compliments the IPET on the extensive work that went into completing this study. It is crucial that the IPET work be easily accessible and understandable to the public and that the IPET makes a strong effort to present its key findings in as clear and organized a manner as possible. This is all the more important given the multi-year delay in completing this study as compared to the original study time table, and the implications this time lapse has had in removing the experience with Hurricane Katrina from the public’s consciousness. Limitations and Key Areas for Improvement The IPET draft final of June 2008 includes eight volumes, a ninth volume of general appendices, and covers roughly 7,500 pages. The report’s eight main volumes naturally are of different sizes and they were produced on different schedules. Some of these volumes were essentially completed in 2006 or 2007 and changed little or not at all since then. In many ways, the IPET report Volume VIII, entitled “Engineering and Operational Risk and Reliability Analysis,” became the most important and prominent volume of the entire study. The research and development entailed in creating the June 2008 version of Volume VIII probably exceeded the IPET team’s original expectations. This NAE/NRC committee’s previous (fourth) report was a specific review of a draft of Volume VIII only, and much of the IPET effort in 2007-2008 was devoted to additional analyses within Volume VIII. It thus is appropriate that this section begin with comments regarding the IPET Volume VIII. It also contains a recommendation regarding interagency cooperation, and concludes with recommendations regarding organization and presentation of the entire IPET draft final report. Volume VIII Among the important findings from Volume VIII is a set of inundation maps for the New Orleans metro region. The results conveyed in these maps are of great importance and interest to citizens, businesses, and government agencies that are making plans for resettlement and redevelopment in this region. Volume VIII presents these important inundation maps, but there is only limited discussion of their implications. Volume VIII would be strengthened by adding an explicit, detailed discussion of the inundation maps and their implications for the spatial distribution of risk across the city and the region.
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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness Volume VIII also would be strengthened by adding an objective, candid discussion of the main limitations of the risk and reliability models used therein, and areas for future improvement. More thorough discussion of all of Volume VIII’s main findings about future vulnerability to the New Orleans region—especially in layman’s terms that are understandable to most decision makers, citizens, and business owners who wish to read the document—is necessary to help them better understand future vulnerabilities and to assist them in their relocation and reconstruction decisions. Interagency Coordination on Flood Inundation Maps In addition to flood inundation maps contained in IPET Volume VIII, the Federal Emergency Management Agency (FEMA) and the National Oceanic and Atmospheric Administration’s (NOAA) National Hurricane Center also produce flood inundation maps for U.S. coastal regions. Although IPET, FEMA, and NOAA have different objectives and product needs, these agencies should engage in ongoing communication and coordinate to ensure consistency among their methods and the resulting products. Full Draft Final Report Volume I of the IPET report, entitled Executive Summary and Overview, contains much interesting and useful information, and readers will turn to it expecting to see primary findings and recommendations. The Volume I Executive Summary is well written, interesting, and informative. There are, however, many disconnections between the Executive Summary in Volume I, and the organization and contents of the rest of the report (Vols. II-VIII). This affects the clarity of key findings and conclusions and diminishes the value of the IPET project. The IPET and the Department of the Army should enlist the services of a firm that specializes in technical writing of scientific and engineering reports to produce a final, summary document of the entire IPET report. The summary should be written in layman’s terminology in order to communicate clearly the IPET study results to decision makers and citizens. LESSONS LEARNED FROM THE KATRINA EXPERIENCE Many of the “lessons learned” in the Hurricane Katrina experience, and presented in this report, represent knowledge widely recognized and
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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness recommended for years by experts and practitioners in the fields of natural hazards, emergency preparedness, civil defense, and other related fields. Unfortunately, much of this information had not been adequately implemented as part of comprehensive hurricane planning and preparedness for the greater New Orleans metro region. This section presents this NAE/NRC committee’s views on the primary lessons learned during the Hurricane Katrina experience, as well as advice on how they might be acted upon and responded to. It reflects the committee’s review of the IPET report and the committee’s collective experience in geotechnical engineering, hurricane wave and storm studies and modeling, water resources planning, and natural hazards mitigation and preparedness. This section is presented in the spirit that in the future, these lessons will be more widely appreciated and understood and that hurricane mitigation and preparedness in this region might be enhanced. Hydrologic Realities and the Limits of Protective Structures There are many inherent hydrologic vulnerabilities of living in the greater New Orleans metropolitan region, especially in areas below sea level. Post-Katrina repairs and strengthening have reduced some of these vulnerabilities. Nevertheless, because of the possibility of levee/floodwall overtopping—or more importantly, levee/floodwall failure—the risks of inundation and flooding never can be fully eliminated by protective structures no matter how large or sturdy those structures may be. Future Footprint of the Hurricane Protection System The pre-Katrina footprint of the New Orleans HPS consisted of roughly 350 miles of protective structures including levees, I-walls, and T-walls. There was undue optimism about the ability of this extensive network of protective structures to provide reliable flood protection. Future construction of protective structures for the region should proceed with this point firmly in mind and in the context of a more comprehensive and resilient hurricane protection plan. Nonstructural Aspects and Options Comprehensive flood planning and risk management for the New Orleans metro region will be based on a combination of structural and nonstructural measures, the latter including relocation options, floodproofing and elevation
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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness of structures, and evacuation studies and plans. Better risk communication also must be part of more effective mitigation and an improved state of preparedness. Structural measures such as levees and floodwalls should not be viewed as substitutes or replacements for nonstructural measures, but rather as complementary parts to a multi-tiered hurricane protection solution. Relocation The planning and design for upgrading the current hurricane protection system should discourage settlement in areas that are most vulnerable to flooding due to hurricane storm surge. The voluntary relocation of people and neighborhoods out of particularly vulnerable areas—with adequate resources designed to improve their safety in less vulnerable areas—should be considered as a viable public policy option. Floodproofing Measures When voluntary relocations are not viable, floodproofing measures will be an essential complement to protective structures—such as levees and floodwalls—in improving public safety in the New Orleans region from hurricanes and induced storm surge. This committee especially endorses the practice of elevating the first floor of buildings to at least the 100-year flood level, and preferably to a more conservative elevation. The more conservative elevation reflects a subsequent finding in this report regarding the inadequacy of the 100-year flood as a flood protection standard for a large urban center such as New Orleans. Critical public and private infrastructure—electric power, water, gas, telecommunications, and flood water collection and pumping facilities—should be strengthened through reliable construction, and ensuring reliable interdependencies among critical infrastructure systems. Evacuation The disaster response plan for New Orleans, although extensive and instrumental in successfully evacuating a very large portion of the New Orleans metropolitan area population, was inadequate for the Katrina event. Thus, there is a need for more extensive and systematic evacuation studies, plans, and communication of evacuation plans. A comprehensive evacuation program should include not only well designed and tested evacuation plans, protocols, and criteria for evacuation warnings, but also alternatives such as improved local
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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness and regional shelters that could make evacuations less imposing. It also should consider longer-term strategies that can enhance the efficiency of evacuations, such as locating facilities for the ill and elderly away from more vulnerable areas that may be subject to frequent evacuations. Risk Communication Before Katrina, there was a limited understanding and appreciation of the residual risks of living behind levees. Improvements in future hurricane preparedness and response will depend partly upon improved public understanding of these risks. In order to enhance the communication and appreciation of these risks, it will be important to extend the efforts of the IPET and to refine, simplify, and communicate consistently the risks of hurricanes and storm surge to the region’s residents, including how those risks vary across the region. Effective communication of the risk-based findings from the entire IPET report will be enhanced by creating a professional summary and compilation of the entire IPET draft report with layman’s terminology (see earlier recommendation in this report). The 100-Year Level of Flood Protection The 100-year level of flood protection is a crucial flood insurance standard. It has been applied widely across the nation and it is being used in some circumstances in reconstruction and planning activities in the New Orleans region. For areas in which catastrophic levee failure is not a major public safety concern, and where large floods would not imperil evacuation routes, the 100-year standard may be appropriate. For heavily-populated urban areas, where the failure of protective structures would be catastrophic—such as New Orleans—this standard is inadequate. Independent Review for Engineering and Design It is important to enlist periodic external review in the design, construction and maintenance of large, complex civil engineering projects such as the New Orleans hurricane protection system. A “second opinion” allows an opportunity to ensure that calculations are reliable, methods employed are credible and appropriate, designs are adequate and safe, potential blind spots are minimized, and so on. An outside external review group also may be able to state politically sensitive findings or facts that a government agency may be reluctant to. Such a review team should be adequately independent of the authority that identified it.
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The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness Periodic Assessments and Updates of Concepts, Methods, and Data Changing environmental conditions can affect the performance and operation of large hurricane and flood protection projects. Advances in scientific and engineering theories and methods may render assumptions on which these projects were based partly or fully obsolete. Because of these changes and the important implications they may have for expected performance of protective structures, a process should be implemented to ensure periodic review of underlying environmental, scientific, and engineering factors that affect New Orleans hurricane protection system performance. The process for incorporating new scientific information into large flood protection projects, like the New Orleans hurricane protection system, can be affected by congressional reauthorization requirements. Changes or clarifications to congressional policies and reauthorizations as they relate to large construction projects may be necessary to effectively implement findings of periodic scientific reviews. The Future of Hurricane Risk Analysis for New Orleans and the Gulf Coast Region The IPET has conducted a landmark assessment of the New Orleans HPS that could serve as a platform for future and ongoing assessments of vulnerability, levels of protection, subsidence rates, geological studies, risk assessments, and so on. As the IPET investigations come to an end, many of the external experts that participated in the studies will return to their respective careers outside the Corps of Engineers. Much of the IPET “institutional memory” therefore may not be infused into Corps of Engineers New Orleans District office, the State of Louisiana, or the City of New Orleans. It is essential that these analyses be extended and subsequently built upon by the Corps of Engineers and others, including the FEMA, NOAA, the State of Louisiana, New Orleans regional municipalities, and the region’s universities, engineers, and scientists. To facilitate future work that builds on the IPET studies, a publicly accessible archive of all data, models, model results, and model products from the IPET project should be created.