Wetland restoration could prevent disastrous flooding.
Tropical storms and hurricanes have surged through much of the Caribbean this month, leaving hundreds dead in flooded Haiti, devastating several other islands and causing havoc along parts of the US coast.
But scientists say that another disaster was only narrowly avoided — Hurricane Ivan missed the deeply vulnerable city of New Orleans by a tiny margin. In the face of future such storms, they are calling for action to restore the area's wetlands, to act as a barrier against flooding.
The Louisiana city was directly in Ivan's path on 14 September, when the storm was classed as ‘Category 5’ with winds upward of 240 kilometres per hour. Almost a million people were evacuated. But Ivan's centre came ashore more than 160 kilometres east of New Orleans on 16 September, and no major flooding was reported in the city.
Scientists warn that a storm is bound to hit New Orleans at some point in the near future, however. Simulations run by the Center for the Study of Public Health Impacts of Hurricanes at Louisiana State University in Baton Rouge show that direct hits by even Category 3 storms would have disastrous consequences. Storm surges could flood the city, which lies in a basin mostly below sea level, to a depth of six metres. This would take weeks to drain. “You're talking about total destruction,” says the centre's director Ivor van Heerden, claiming that deaths could be in the tens of thousands.
Greg Stone, director of the Coastal Studies Institute at Louisiana State University, thinks the city's levees would hold after an assault from a Category 3 hurricane — but not from a Category 4 or 5 storm. Both scientists agree that the mayor was correct in urging the city's 1.3 million residents to flee.
Restoring barrier reefs and marshlands in the delta between the city and the Gulf of Mexico is the best way to mitigate the threat, the researchers say. The wetlands have been steadily eroded since the 1930s owing to extensive embankments built to control flooding of the Mississippi river. These prevent water and sediment from reaching the delta. “We are literally starving our wetlands to death,” says van Heerden.
A 30-year restoration plan, called Coast 2050, was published in 1998. But arguments over who should foot the $14-billion bill have stalled the plan in Congress ever since. Stone and other scientists were planning to brief Louisiana's congressional delegation on coastal restoration this week.
The hurricane season, which is currently at the peak of a 30–40 year cycle, is expected to continue for a few more months.
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Reichhardt, T. Hurricane Ivan highlights future risk for New Orleans. Nature 431, 388 (2004). https://doi.org/10.1038/431388b
Integrated Environmental Assessment and Management (2011)