Structural Performance of the New Orleans Hurricane Protection System During Hurricane Katrina Letter Report (2006) / Chapter Skim
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Letter Report
Letter Report
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Although most of the protection structures along Lake Pontchartrain were not overtopped, hydraulic forces caused breaches of floodwalls along New Orleans' 17th Street Canal and the London Avenue Canal. Flooding in the New Orleans region resulted in the loss of hundreds of lives and catastrophic property and infrastructure damage, ranking it among the largest natural disasters in U.S.
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, supplemented by information presented by IPET team members and by representatives of the ASCE ERP at our committee's first meeting, held in New Orleans on January 18, 20061. CONTEXT OF THE INTERAGENCY PERFORMANCE EVALUATION TASK FORCE STUDIES The New Orleans and southeastern Louisiana hurricane protection system includes many engineering, geologic, hydraulic and hydrologic, administrative, and economic and cultural features that interact in complex ways.
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The work required to identify, recruit, and coordinate the efforts of federal and non-federal engineers and scientists, lay out an overall study structure and work plan, convene numerous meetings and conference calls, and begin data analysis and model construction on many fronts, has been considerable. Our committee is impressed with the extent of the IPET efforts and commends the IPET for the energy devoted to its tasks and for the progress achieved in a short amount of time.
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Systems-wide Perspectives Data collection and analytical efforts to date appear to be focused on particular aspects of the event and specific sites, as opposed to system-wide analyses. For example, the IPET first report has a strong focus on analyzing conditions at specific breach sites, with less emphasis on 2These 10 study areas are: data collection and management; geodetic vertical and water level datum assessment; hurricane surge and wave analysis; hydrodynamic forces analysis; geotechnical structure performance analysis; floodwall and levee system performance analysis; pumping station performance analysis; interior drainage/flooding analysis; consequence analysis; and risk and reliability analysis.
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" As noted, the IPET program includes extensive data collection efforts and a great deal of highly technical analysis. Some IPET study stakeholders may have unclear expectations about the quality and completeness of the information that will ultimately result from the IPET effort.
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The final IPET products are scheduled to be completed by June, 2006, which represents a nine-month time period for the entire study. The time constraints imposed on the IPET are not conducive to thoughtful and comprehensive analysis and may force IPET team members, many of whom appear to be working around the clock, to make hasty decisions with little time to learn and to make appropriate mid-course corrections.
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Discussions with IPET team members suggest that IPET is working to develop and present this picture of overall regional geology, and the IPET is encouraged to continue developing this portrayal of regional geologic conditions. Data Gathering The Data Repository, described in Appendix G in the first IPET report, is organized to be comprehensive, with detailed information for each part of the New Orleans levee and flood wall system, including base maps, climate, design criteria, field investigations, geology, hydrology, lab test data, modeling, soil conditions, and other data.
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To the extent that the IPET team may have made post-January 18 progress on this front, they should be encouraged to continue to do so. 17th Street and London Avenue Breaches Foundation conditions are of particular importance at the sites of the breaches at 17th Street and London Avenue Canals (where there is no evidence of overtopping)
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The IPET first report provided little information on the likely failure mechanisms at either the 17th Street or London Avenue breaches. And although the limit equilibrium and finite element analyses listed in the IPET report are reasonable, accepted engineering practice would entail a summary of current and estimated soil properties and an initial evaluation of potential failure mechanisms at these key breaches.
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Fulfillment of IPET objectives to assess storm-related conditions during Hurricane Katrina and the future risks associated with the current protection system require that the storm surge and wave models capture the dominant features and processes of the study area The IPET has placed a strong emphasis on hurricane surge and wave analysis and has made good progress in this area. Future efforts should include clearly documenting how the dominant physical processes are represented and parameterized in the corresponding models.
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· There should be stronger emphasis on explaining connections between data collection efforts and overall study objectives, and in explaining linkages and transitions among the 10 study topics. · There should be stronger emphasis on evaluating overall, regional hurricane protection system strength and vulnerabilities.
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· The IPET study would be enhanced by some explanation of how IPET activities fit into the larger context of overall recovery. · Efforts at gathering data on in situ soil properties and on soil and geologic profiles, and on conducting comprehensive studies of soil properties, should be strongly emphasized.
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13 Committee Membership G Wayne Clough, Chair, Georgia Institute of Technology, Atlanta Rafael L
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, interior drainage systems models, numerical models of the Hurricane Katrina surge and wave environment, storm surge and wave physical modeling of hydrodynamic forces and centrifuge breaching, geodetic vertical survey assessment, and the analysis of floodwall and levee performance.
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