Hearings - Testimony
 
Field Hearing
Oversee the Ongoing Rebuilding and Restoration Efforts of Hurricane and Flood Protection by the Army Corps of Engineers
Tuesday, April 18, 2006
 
Dr. Lewis E. Link
Director, Interagency Performance Evaluation Task Force (IPET)

Mr. Chairman and distinguished members of the committee, I am Dr. Lewis E. Link, Senior Research Engineer in the Department of Civil and Environmental Engineering, University of Maryland and Project Director, Interagency Performance Evaluation Task Force. It is with great respect and appreciation that I submit this testimony concerning the activities of the Interagency Performance Evaluation Task Force, IPET. The IPET was commissioned by the Chief of the U.S. Army Corps of Engineers shortly after Hurricane Katrina devastated southeast Louisiana and southern Mississippi. The task force was charged to determine the facts concerning the performance of the southeast Louisiana hurricane protection system during Katrina, to report those facts to the public and to quickly facilitate the integration of these facts into the repair and reconstitution of the hurricane protection system.

 

To accomplish this mission, the IPET has assembled a broad array of national experts from federal and state agencies, academia and industry. More than 150 recognized experts from over 50 organizations comprise the IPET teams. Leadership is provided from within and external to the Corps of Engineers for each major task area. The American Society of Civil Engineers External Review Panel is providing direct peer review of IPET activities as we proceed. Also, the National Research Council Committee on New Orleans Regional Hurricane Protection Projects is providing strategic oversight and independent review of IPET work as well as information from other sources studying Katrina.

IPET information and analysis is provided to the public through a public web site (https://IPET.wes.army.mil) that currently provides over 3900 documents and reports on the New Orleans Hurricane Protection System and the IPET work. This web site is also used to solicit feedback and input from the public on IPET documents and for information needed such as eye-witness accounts of when specific breaching events occurred. IPET Report 1, Performance Evaluation Plan and Interim Status, posted on the web site on January 10, 2006, provides a detailed scope of work and plan for the IPET activities. IPET Report 2, Performance Evaluation Status and Interim Results, posted on the web site on March 10, 2006, provides the most recent documentation of the IPET analyses and the emerging results. The IPET final draft report, Report 3, Performance Evaluation of the New Orleans and Vicinity Hurricane Protection System, is scheduled to be available as a final draft on June 1, 2006. Following a review of this final draft report by both the ASCE ERP and the National Academies, a final IPET report will be released in the fall of 2006.

The IPET effort has been directly tied to the efforts of Task Force Guardian, the Corps team managing the rapid repairs of the protection system, and other Corps elements. Over 20 individuals from Task Force Guardian and the New Orleans District participate in the various IPET teams, providing direct access to critical knowledge and information needed for the IPET analysis. This coordination also provides a direct pipeline to transfer emerging IPET results and lessons learned immediately into the design and construction of repairs to the Hurricane Protection System. The last section of this written testimony includes a summary of the types of products IPET has provided to Task Force Guardian. It is critical that these lessons learned are incorporated immediately into the design and construction process as they are established to ensure we have the optimum repair designs to address IPET identified problems. The IPET lessons learned are also being provided to the Corps to provide a basis for future design and construction to recover the system to authorized protection levels and to complete the authorized Hurricane Protection System. The IPET results and methods will also provide a basis for Corps Headquarters efforts to review and renew engineering policy and practice as well as providing a new level of capabilities for studying future alternative protection measures for New Orleans and the vicinity. IPET results will ultimately help provide better and stronger designs for future protection projects in Louisiana and possibly other protection systems nation wide.

The following paragraphs describe the IPET efforts ongoing to answer the major questions that comprise the mission of the task force.

1. Geodetic Datum: The complex geology of southeast Louisiana provides the additional challenge of variable and relatively rapid subsidence. To accomplish the IPET analysis, it was essential to have an up-to-date geodetic and water level reference system to accurately measure the vertical elevations of all significant structures relative to local mean sea level. IPET accelerated the efforts of the Corps and National Geodetic Survey to update the local and regional reference datum using Global Positioning System, or GPS, technology. IPET also established the accurate elevations of the levees, floodwalls, pumping stations and other relevant structures to support the performance analysis. This provided an accurate reference system for all entities working on the analysis and reconstruction of the hurricane protection system. It also provided an accurate definition of the heights of the protection system structures at the time of Katrina. These revised and accurate elevations will aid future work to achieve the original authorized levels of protection or to any new levels prescribed by future policy or congressional authorizations. They will also be used by the construction industry and others in southern Louisiana for projects that rely on correct elevations relative to the local water surface.

2. Hurricane Protection System Characterization: The Hurricane Protection System is comprised of over 350 miles of levees and floodwalls. To understand the system’s performance, it is necessary to understand the design criteria, the design assumptions and the “as built” characteristics of the individual structures. To accomplish this, the IPET has done a systematic examination of the documents concerning design and construction of the system to include the Standard Project Hurricane definition, the translation of the Standard Project Hurricane into surge and wave levels to develop design elevations, the fundamental design of the structures and the intent of the designers and the character of the structures as built. These results are the fundamental inputs to the performance analysis. With the exception of some systematic differences in elevations due to broad misinterpretations of local mean sea level, to date, this comprehensive review and analysis has not found any significant disparities between the fundamental designs and the as-built character of the system.

3. Storm Analysis: Katrina was a very large storm, generating perhaps the largest storm surge measured for the North American Continent and the largest waves on our continental coast measured by a NOAA buoy, approximately 55 feet. This created a hydrodynamic environment that was in some cases significantly greater than the Hurricane Protection System was designed to handle. This was particularly the case for the areas along the Mississippi River Gulf Outlet and the levees in Plaquemines Parish. The water elevations within the Inner Harbor Navigation Canal also exceeded the design levels. Coupled with the fact that many of these areas had actual levee elevations below authorized/design levels, resulted in significant overtopping of levees in these locations. Of particular significance was the fact that the waves striking the MRGO and Plaquemines levees had wave periods of up to three times the design criteria, essentially representing ocean waves, leading to much more wave run up and much more destructive force than anticipated by the original design. The IPET simulations of Katrina surge and wave levels were run on some of our nation’s most powerful supercomputers are some of the most advanced modeling efforts in engineering. These simulations resulted in a high resolution definition of the surge water levels and wave environments experienced by each section of levee or floodwall as a function of time. IPET coupled these data with the definition of the times of the breaching events, which allow determination of the specific water levels and wave forces that the individual structures experienced during the breaching process. One of the primary lessons learned here was the need for very accurate wind information and very high resolution computer grids for accurately modeling the storm and the resulting surge and wave conditions in the vicinity of the actual structures. High water marks were used as the primary calibration for these modeling efforts.

4. Performance Analysis: The IPET performance analysis uses a combination of approaches to achieve an understanding of the most likely breaching mechanisms for the individual breach sites. The approaches include detailed field investigations, finite element or other computer simulations, conventional seepage or stability analysis, and physical modeling, both in centrifuges and a 1:50-scale hydraulic model of the 17th Street Canal. The performance analysis of the 17th Street Canal breach, as reported in IPET Report 2, provides an example of the level of detail and analysis methods used. Additional finite element analysis has been accomplished for the 17th Street site that will be released in the near future. The detailed definition of the breaching mechanism is necessary to determine the appropriate repair and reconstruction needed to make these sections more resilient in the future and to determine how to assess the integrity of similar structures that were not severely damaged by Katrina. Similar analyses are being completed for the London Avenue and Inner Harbor Navigation Canal breach sites. A separate analysis is ongoing to understand the performance of the levee sections along MRGO and Plaquemines Parish, focusing on the surge and wave levels experienced, the degree of scour and erosion experienced, the character of the materials in the levee and their placement and the true elevation of each section. These results will be documented and reported within the next month. The breaching mechanisms, and the understanding of why other similar sections did not fail, are vitally important. This information is being directly input in the assessment of the remaining sections of the Hurricane Protection System and to define the probability of different levels of performance of different component structures for the IPET risk and reliability analysis.

5. Consequences: The amount of flooding resulting from the overtopping and breaching of the system during Katrina is being modeled for each drainage area. This capability, along with the characterization of the performance of the pumping stations, provides an ability to examine other scenarios. An example of such a scenario is the extent of flooding if there had been no catastrophic breaching in the system. The losses experienced during and as a result of Katrina are being characterized on a zip code and census block basis. Economic (domestic and commercial), environmental, life and safety and historical/social losses are being characterized. This information will allow correlation of consequences to physical performance. The life and safety and economic losses are also being incorporated into the IPET risk and reliability assessment. The completed consequence products will be released in the IPET final report on June 1.

6. Risk and Reliability: A risk and reliability assessment is being accomplished to provide a system– wide examination of the relative vulnerability of the various drainage basins (polders or parishes) to flooding and losses, given the condition and character of the components of the hurricane protection system on June 1. This work incorporates both stage - frequency and stage - damage relationships that offer the opportunity to examine risk individually at the zip code or census block level or consolidated up to sub basins, basins or polders, parish or system-wide levels. It also allows examination of the impact of changing the character of the protection for a given reach, providing a means to examine how alternative approaches to protection can reduce risk. The risk information for Katrina and for the repaired system as of June 1, 2006, will be provided for the East Bank Polders in the IPET final report.

The vast bulk of the IPET analyses are expected to be completed on time and reported by June 1, 2006. The final draft of Report 3 will remain subject to revision until the final comments of the ASCE External Review Panel around July and the NRC Committee on New Orleans Regional Hurricane Protection Projects are received in September and incorporated into the report.

I appreciate the opportunity to provide this information and pledge the continued dedication of the IPET efforts to the objective analysis of the performance of the hurricane protection system. We are all working toward the common goal of applying lessons learned to the repair, reconstruction and improvement of hurricane protection in New Orleans and southeast Louisiana.

 

 

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