The New Orleans Hurricane Protection System Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness (2009) / Chapter Skim
Currently Skimming:
3 Lessons Learned in Hurricane Katrina and Its Aftermath
3 Lessons Learned in Hurricane Katrina and Its Aftermath
Pages 21-36
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From page 21... ...
Careful appraisal of the root causes of those impacts, and the identification of viable actions for improving preparedness, are essential for reducing the prospects of the recurrence of such an event in the future. This chapter offers technical, organizational, and policy recommendations for improving hurricane preparedness for New Orleans and southeastern Louisiana and responds to the portion of this committee's statement of task to "determine lessons learned from the Katrina experience and identify ways that hurricane protection system performance can be improved in the future at the authorized level of protection." The chapter is based on 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.
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From page 22... ...
Modern protective structures and diligent maintenance and repair efforts can help reduce the risks of hurricanes and storm surge. In fact, the ability of these structures to help protect against storm surge was demonstrated in New Orleans during Hurricane Gustav in early September 2008.
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From page 23... ...
In fact, in many cases, they can create significant and potentially catastrophic residual risk that may increase if conditions in the region change, if levees are affected by natural events, or if the levees are not properly maintained" (Interagency Levee Policy Review Committee, 2006; italics in original)
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From page 24... ...
. Other relevant quotes from the ASFPM paper for this committee's report and hurricane and storm surge protection in New Orleans are: In those cases in which a levee is found to be an appropriate mea sure to protect urban areas or to be credited for protection, the levee should be constructed to a high level of protection.
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From page 25... ...
As with many structures built to protect against riverine or coastal flooding, the Lake Pontchartrain and Vicinity Hurricane Protection Project promoted a false sense of security that areas behind the structures were absolutely safe for habitation and development. Unfortunately, there were substantial "residual" risks in these areas behind the protective structures that never were adequately communicated to the public and that were not adequately considered in the settlement of many of these areas.
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From page 26... ...
Furthermore, regardless of the level of investments, the residual risks of hurricane storm surge always will be significant for some areas behind these protective structures. LESSON: The pre-Katrina footprint of the New Orleans HPS consisted of roughly 350 miles of protective structures including levees, I-walls, and T-walls.
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From page 27... ...
For those many structures and residents in vulnerable areas that are not amenable to relocations, major floodproofing measures are recommended in order to improve public safety from hurricane storm surge. This committee especially endorses the practice of elevating the first floor of building to at least the 100-year flood level, and preferably to a more conservative elevation.
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From page 28... ...
LESSON: 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.
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From page 29... ...
Finding the correct balance between public safety concerns and the issuance of evacuation orders as a storm approaches, while trying to minimize possible evacuation fatigue, is a challenging decision process for elected officials and emergency managers. As no structure can ensure complete protection against all floods and storm surges, an efficient evacuation program will be a part of comprehensive hurricane protection.
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From page 30... ...
To ensure public safety, residents must be evacuated well in advance of approaching hurricanes, and considering uncertainties in storm paths, the decision heavily favors issuing an evacuation order "better safe than sorry." This means that there will be evacuations in areas and cities that ultimately are not affected by a given storm, and a city or region may have multiple, legitimate evacuations in a single season with no actual storm damage. Evacuation fatigue can result from repeated evacuation orders and will affect the decision making of public officials and the effectiveness of future evacuations.
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From page 31... ...
. Effective communication of the vulnerabilities of the New Orleans region to hurricanes and storm surge will encompass many of the concepts discussed in this report and evaluated in the IPET report, such as uncertainties of storm surge inundation estimates, changes in vulnerabilities over time, effective evacuation planning, and so on.
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From page 32... ...
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 heavilypopulated urban areas, where the failure of protective structures would be catastrophic -- such as New Orleans -- this standard is inadequate.
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From page 33... ...
LESSON: 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.
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From page 34... ...
This level of protection was derived from the standard project hurricane stillwater design storm surge used in 1962 (Ibid.)
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From page 35... ...
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.
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From page 36... ...
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.
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