BY HENRY PETROSKI

Putting New Orleans on higher ground could help prevent future flood disasters.

THE PHENOMENON OF Grade inflation has been widely discussed among academics in recent years, but there is another kind of grade raising there that may have more relevance after Hurricane Katrina's disastrous flooding in New Orleans. There are some historical precedents that suggest grade raising as a possible solution to the city's chronic vulnerability due to its below-sea-level location.

In the mid-nineteenth century, Chicago was prone to flooding, which caused epidemics of cholera and dysentery. To improve drainage, Boston engineer Ellis Chesbrough recommended that Chicago construct a large-capacity sewer system, laying the pipe directly on the existing street grade and covering it with 6 to 10 feet of dirt. This raised the grade of the city, of course, and buildings had to be jacked-up to conform to it.

Unfortunately, whatever the sewers carried, including waste from Chicago's large meat-packing industry, was dumped directly into the Chicago River, which carried it into Lake Michigan, the source of the city's water supply. To protect the lake, the direction of the flow of the river was reversed. This and the grade raising were enormous undertakings at the time, but they show what can be done by a city with the will to do it.

Galveston, Texas, was struck by a huge storm surge in 1900, which inundated the island city and killed at least 6,000 people. An engineering committee recommended building a large sea wall and raising the grade of the city to prevent such a disaster in the future. To raise the city, buildings and walkways were supported on stilts while dredged-up sand was pumped beneath them.

Moving large quantities of sand, dirt, rocks or stones are familiar construction tasks. It is how the Egyptian pyramids were built. Even today, structures large and small begin with digging a foundation. Similarly, large quantities of material have to be moved in tunneling, canal digging and other great projects, such as Boston's Big Dig.

It would not take any great advances in technology to raise the grade of New Orleans. And given the recent devastation caused by flooding, this might be the time to do it. Since the vast majority of the population has been relocated and great numbers of houses may have to be rebuilt, a grade raising could proceed without much additional disruption.

But what is technically possible and logistically practical is not necessarily the right thing to do at a given time. The idea of raising the grade of New Orleans may be appealing to engineers, but it will be politicians, civic leaders and the citizens themselves who will have the most to say about how the city should be rebuilt.

Such extratechnical considerations as the historical nature of the city, its familiar grades and elevations and even its cachet as a city that parties below sea level are likely to influence decision making at least as much as technical assessments.

Just as there is no easy way to resolve the debate over grade inflation at colleges and universities, so it would not be an easy matter to get all interested parties in New Orleans to agree on whether to raise its street grade in low-lying areas. Engineers know this, of course, but it is still in their nature to put all possible solutions on the table.

Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His latest book is "Pushing the Limits: New Adventures in Engineering."