It is time to swim against the tide. The direction of public discourse in the wake of Katrina goes like this: First we save lives and provide some basic assistance to the victims. Then we clean up New Orleans. And then we rebuild the city. Most will rightly agree on the first two. But should we rebuild New Orleans, 10 feet below sea level, just so it can be wiped out again?
Some say we can raise and strengthen the levees to fully protect the city. Here is some unpleasant truth: The higher the defenses, the deeper the floods that will inevitably follow. The current political climate is not conducive to having scientific arguments heard before political decisions are made. But not doing so leads to the kind of chaos we are seeing now.
This is not a natural disaster. It is a social, political, human and -- to a lesser degree -- engineering disaster. To many experts, it is a disaster that was waiting to happen. In fact, Katrina is not even the worst-case scenario. Had the eye of the storm made landfall just west of the city (instead of to the east, as it did) the wind speeds and its associated coastal storm surge would have been higher in New Orleans (and lower in Gulfport, Miss.). The city would have flooded faster, and the loss of life would have been greater.
What scientific facts do we need before making fateful political, social and economic decisions about New Orleans's future? Here are just two:
First, all river deltas tend to subside as fresh sediment (supplied during floods) compacts and is transformed into rock. The Mississippi River delta is no exception. In the early to mid-20th century, the Army Corps of Engineers was charged with protecting New Orleans from recurring natural floods. At the same time, the Corps kept the river (and some related canals) along defined pathways. These well-intended defensive measures prevented the natural transport of fresh sediments into the geologically subsiding areas. The protected land and the growing city sank, some of it to the point that it is now 10 feet below sea level. Over time, some of the defenses were raised and strengthened to keep up with land subsidence and to protect against river floods and storm surges. But the defenses were never designed to safeguard the city against a direct hit by a Category 5 hurricane (on the Saffir-Simpson scale) or a Category 4 hurricane making landfall just west of the city.
Second, global sea levels have risen less than a foot in the past century, and will rise one to three feet by the end of this century. Yes, there is uncertainty. But there is no doubt in the scientific community that the rise in global sea levels will accelerate.
What does this mean for New Orleans's future? Government officials and academic experts have said for years that in about 100 years, New Orleans may no longer exist. Period.
It is time to face up to some geological realities and start a carefully planned deconstruction of New Orleans, assessing what can or needs to be preserved, or vertically raised and, if affordable, by how much. Some of New Orleans could be transformed into a "floating city" using platforms not unlike the oil platforms offshore, or, over the short term, into a city of boathouses, to allow floods to fill in the 'bowl' with fresh sediment.
If realized, this "American Venice" would still need protection from the worst of storms. Restoration of mangroves and wetlands between the coast and the city would need to be carefully planned and executed. Much engineering talent would have to go into anchoring the floating assets to prevent chaos during storms. As for oil production, refining and transshipment facilities, buffer zones would have to be established to protect them from the direct onslaught of coastal storm surges.
Many ancient coastal cities of great fame have disappeared or are now shells of their former grandeur. Parts of ancient Alexandria suffered from the subsidence of the Nile delta, and earthquakes and tsunamis toppled the city's famed lighthouse, one of the "Seven Wonders of the Ancient World."
It is time that quantitative, science-based risk assessment became a cornerstone of urban and coastal land-use planning to prevent such disasters from happening again. Politicians and others must not make hollow promises for a future, safe New Orleans. Ten feet below sea level and sinking is not safe. It is time to constructively deconstruct, not destructively reconstruct.
The writer, a geophysicist, is an adjunct professor at Columbia University's School of International and Public Affairs. He teaches and does research on disaster risk management.