. Earth Science News .
Subsidence in New Orleans abetted hurricane disaster: study

Scientists discovered after Hurricane Katrina that water levels exceeded those expected for the storm by between 90cm (35 inches) and 1.7m (66 inches). Photo courtesy of AFP.
by Staff Writers
Paris (AFP) May 31, 2006
Areas of New Orleans had been sinking for years before Hurricane Katrina flooded the city, and the worst subsidence occurred at levees that were easily breached by the storm's surge, a study says.

"Parts of New Orleans underwent rapid subsidence in the three years before Hurricane Katrina struck in August 2005," says the paper, published in the British science journal Nature and authored by a University of Miami team.

The evidence comes from radar images taken from 2002 to 2005 by a Canadian satellite, RADARSAT.

Carefully overlaid, the 33 images show that, overall, the city sank by an average of 5.6 millimetres (0.22 inches) a year during this time.

As global sea levels, driven by the greenhouse effect, are rising by around 2mm (0.07 inches) a year, this means the city was subsiding relative to the sea at around 8mm (0.3 inches) annually.

But the study says the subsidence is likely to have carried on over a much longer term -- and some parts of the city had been sinking much faster than others.

It cited the districts of Lakeview, on the south shore of Lake Pontchartrain; Kenner, near Louis Armstrong New Orleans International Airport in east New Orleans; and regions bordering St. Bernard Parish, west of Lake Borgne.

In this latter area, subsidence ran at at more than 20mm (0.8 inches) a year from 2002 to 2005, especially at the levee system along the Mississippi River-Gulf Outlet (MRGO), a canal where some of the worst breaches in flood protection occurred.

Stealthy subsidence over many years would mean that the levees could be easily topped by the storm surge without engineers being aware of the problem.

Scientists discovered after Katrina that water levels exceeded those expected for the storm by between 90cm (35 inches) and 1.7m (66 inches).

Another possibility, though, is that the subsidence promoted failure at the base of the levees, enabling the walls to be smashed aside by the surge.

As for the cause of the subsidence, the paper points the finger at the drainage of wetlands, causing highly organic soil to get dried out and compacted, although in eastern New Orleans, an active fault may have increased the problem.

Lead author is Timothy Dixon, of the University of Miami's Rosenstiel School of Marine and Atmospheric Science.

Related Links

Pleas for help as Indonesia defends quake aid
Bantul, Indonesia (AFP) Jun 1, 2006
Indonesia defended the earthquake relief effort as angry survivors pleaded for help and aid agencies said many victims lacked medical care and water four days after the disaster.







  • US develops hurricane evacuation plans for pets
  • Pleas for help as Indonesia defends quake aid
  • Subsidence in New Orleans abetted hurricane disaster: study
  • Extending The Reach Of Disaster Relief From Fire To Flood

  • Climate change could fuel fiercer hurricane cycles: researchers
  • Climate change: Arctic went from greenhouse to icehouse
  • Sea-Surface Warming Linked to Worse Tropical Storms Activity
  • Cutting Energy Waste Crucial To Forestalling Climate Change

  • Ancient City Reveals Life In Desert 2,200 Years Ago
  • Commercial Remote Sensing Satellite Market Stabilizing
  • Digital Globe and Getty Images To Supply Satellite Images To News Media
  • Intermap Technologies Receives Radar Mapping Contract

  • Oil prices retreat as US offers talks with Iran
  • Crude oil prices rise amid Iran concerns
  • EU offers tips on cutting greenhouse gases
  • GE to invest 50 mln dlrs in environment-related R and D in China

  • UN Reports AIDS Progress, But
  • Deaths Mount In Indonesia
  • Malaria, Potato Famine Pathogen Share Surprising Trait
  • Microbe Labs Proposed For California

  • Marauding monkeys wreak havoc on Zanzibar isle
  • DNA Diet Makes For Some Vibrant Bugs
  • Astrobiologist Meet In Sweden
  • Overfishing Puts Southern California Kelp Forest Ecosystems At Risk

  • Pollution turning China's Yangtze river "cancerous"
  • 'Mercury Sponge' Technology Goes From Lab To Market
  • Managing Indian E-Waste
  • Finland hopes to clean up Russian shipping in Baltic

  • Ancient Etruscans Unlikely Ancestors Of Modern Tuscans
  • MIT Poet Develops 'Seeing Machine'
  • Robotic Joystick Reveals How Brain Controls Movement
  • Cure For Reading Glasses May Be In View

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement