New Orleans Sinking Faster than Thought
Parts of New Orleans are sinking an inch a year, according to new findings.
Everyone has known New Orleans is a sinking city. Now new research suggests parts of the city are sinking even faster than many scientists imagined — more than an inch a year. That may explain some of the levee failures during Hurricane Katrina and it raises more worries about the future.
The research, reported in the journal Nature, is based on new satellite radar data for the three years before Katrina struck in 2005. The data show that some areas are sinking four or five times faster than the rest of the city. And that, experts say, can be deadly. “My concern is the very low-lying areas,” said lead author Tim Dixon, a University of Miami geophysicist. “I think those areas are death traps. I don’t think those areas should be rebuilt.”
The blame for this phenomenon, called subsidence, includes overdevelopment, drainage and natural seismic shifts. For years, scientists figured the city on average was sinking about one-fifth of an inch a year based on 100 measurements of the region, Dixon said. The new data from 150,000 measurements taken from space finds that about 10 percent to 20 percent of the region had yearly subsidence in the inch-a-year range, he said. As the ground in those areas sinks, protection from levees also falls, scientists and engineers said. For example, the Mississippi River Gulf Outlet, built more than three decades ago, has sunk by more than 3 feet since its construction, Dixon said, explaining why water poured over the levee and part of it failed.
This may renew the “should we rebuild” debates that followed Katrina. If nothing else, these findings will have to be taken into account when planning.