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The Lessons of Katrina

Jul 1, 2015

Ten years ago this August, Hurricane Katrina tore along the U.S. Gulf Coast, causing more than 1,800 fatalities and more than $100 billion in damage. Nowhere was the hurricane's destruction more catastrophic than in the city of New Orleans, where the levee system proved inadequate against the storm surge. Some 80 percent of the city and its neighboring parishes were submerged in floodwater, and it was here that the death toll was heaviest. This column seeks to highlight a few of the ethical issues raised by one of the deadliest engineering-related disasters in U.S. history.


What ethical lessons can be drawn from the New Orleans levee system failures during Hurricane Katrina?


Many of history's best-known engineering failures can be traced to a single, catastrophic design flaw, for example, the faulty O rings in the space shuttle Challenger and the inadequate connections in the Hyatt Regency walkway collapse in Kansas City, Missouri. Although the engineering causes of the New Orleans levee system failure are far more complex and diffuse, the Katrina disaster bears one distinct similarity with these other engineering failures-namely, that the failure did not occur because of the design flaws alone but because of a series of faulty decisions by the individuals charged with designing and managing the system. These decisions, in combination with the design flaws, led to a tragic result

Canon 1 of ASCE's Code of Ethics is certainly applicable: "Engineers shall hold paramount the safety, health and welfare of the the performance of their professional duties," and category (a) in the guidelines to practice for this canon adds the following: "Engineers shall recognize that the lives, safety, health and welfare of the general public are dependent upon engineering judgments, decisions and practices." The recognition described in this guideline implies more than a mere abstract awareness of the engineer's duty to the public; it requires the engineer to be untiringly vigilant in preserving the interests of the men, women, and children whose lives may be affected by the engineer's actions.

Yet the decades leading up to the Katrina disaster bore witness to a pattern of decisions in which compromises in the safety and reliability of the New Orleans levee system were made for reasons having to do with cost, scheduling, or political pressure. Instead of a single flaw serving as the direct cause of the failures, the hurricane protection system as a whole was significantly underdesigned for its purpose, which represented an overall lapse in vigilance on the part of the engineers and other decision makers in their obligation to protect the residents depending on the levees.

One example of these compromises in safety lay in the U.S. Army Corps of Engineers' calculation of soil strength for the 17th Street Canal levee and floodwall. The Corps engineers based their estimate of soil strength below the canal on boring samples spaced across a 1.5 mi distance, but the New Orleans area is characterized by high variability in soil strength. Although the engineers used a target factor of safety to account for this variation, they chose a value of 1.3, which is at the low end of generally accepted engineering values and below the Corps's own engineering guidelines. While not the key factor in the failure of the 17th Street Canal levee, the combination of a nonconservative interpretation of sample data and a low factor of safety led the engineers to overestimate the average soil strength by some 30 percent in their design

A second example involved the decision to design the levee system for a less severe hurricane. The Corps chose to model its system on what it defined as a standard project hurricane, which incorporated the most severe parameters that were "reasonably characteristic" of the region. On the basis of U.S. Weather Bureau projections of wind speeds of 101 to 111 mph as representative of the area, the engineers once again chose data at the low end of the spectrum and designed the system for Lake Pontchartrain and the vicinity for a surface wind speed of 100 mph. Moreover, when the National Weather Service (as the successor of the U.S. Weather Bureau) later raised its projected maximum wind speeds to 151 to 160 mph, the Corps failed to update its standard project hurricane assumptions or to alter its design to match the new data. Thus, the system modeled for lower wind speeds was incapable of handling Katrina's 125 mph winds and associated storm surge

Still another example of safety compromises involved the heights of the levee structures. The Corps designed the levee system relative to mean sea level, but many structures were built with reference to land-based datums that were incorrectly believed to be equal to local mean sea level. Moreover, despite knowing that the New Orleans region is subsiding at a rate of roughly 0.2 in. per year, the Corps declined to make an allowance for this subsidence in its design, a decision attributed to a congressional restriction on considering water above "authorized levels." In such areas as the Industrial Canal, the combination of improper elevation data and subsidence meant that the structures were a full 2 ft lower than called for in the design

These are a few simple examples of the complex problems affecting the readiness of the New Orleans levee systems for an extreme storm. In fact, the engineering and design issues as a whole are only part of the story behind Katrina's devastating impact. Additional problems brought to light in postdisaster assessments of the hurricane protection system include failures of coordination on the part of federal, state, and local agencies; the absence of a central authority with responsibility for the system; a poor funding mechanism and pressures from government to lower design standards to increase affordability; and the failure of city disaster planners to mitigate the risk with more effective evacuation procedures

Nevertheless, if the engineer's ethical duty is to hold paramount the safety, health, and welfare of the public, then the Katrina disaster demonstrates the costs of failing to be vigilant in honoring that duty. As the persons best qualified by education and experience to understand the ramifications of technical decisions, it is essential that engineers question decisions that compromise safety or reliability and that they clearly communicate risks and consequences when they believe a course of action poses too great a threat to the public. Moreover, as the individuals with the greatest understanding of the limitations of engineered systems, it is crucial that engineers be forthright in acknowledging these limitations and that they ensure that the affected parties understand the risks and are prepared for untoward events

Given the degree of danger posed by extreme storms and the importance of hurricane protection systems, it is essential for engineers to recognize the ethical dimensions of building such systems on the basis of nonconservative judgments and minimal margins of safety. And while the words of canon 1 may not provide all of the answers for preventing another Katrina, the guidance it provides is unquestionably valuable. In its report The New Orleans Hurricane Protection System: What Went Wrong and Why , ASCE's External Peer Review put it this way:

Although the conditions leading up to the New Orleans catastrophe are unique, the fundamental constraints placed on engineers for any project are not. Every project has funding and/or schedule limitations. Every project must integrate into the natural and man-made environment. Every major project has political ramifications. 

In the face of pressure to save money or to make up time, engineers must remain strong and hold true to the requirements of the profession's canon of ethics, never compromising the safety of the public. Organizations must be structured to enable, not to inhibit, this focus on safety. Engineers must continually evaluate the appropriateness of design criteria. They must always consider how the performance of individual components affects the overall performance of a system. 

Thus, whether the project is small or large and whether it affects a limited group or an enormous community, canon 1 serves to remind engineers of their fundamental role as champions for safety in all their professional duties.

Members who have an ethics question or would like to file a complaint with the Committee on Professional Conduct may call ASCE's hotline at (703) 295-6151 or (800) 548-ASCE (2723), extension 6151. The attorneys staffing this line can provide advice on how to handle an ethics issue or file a complaint. Please note that individual facts and circumstances vary from case to case, that some details may have been altered for purposes of illustration or confidentiality, and that the general summary information contained in these case studies is not to be construed as a precedent binding upon the Society.

© ASCE,  Civil Engineering , July 2015