Delta Sinking Slower Than Thought, Tulane Study Says

February 19, 2006

Michael Strecker
Phone: (504) 865-5210

While erosion and wetland loss is a huge problem along Louisiana's coast, the Earth's crust below much of the Mississippi Delta is surprisingly stable and appears to be subsiding at a much slower rate than currently thought, according to a new study by Torbjörn Törnqvist, an associate professor of earth and environmental sciences at Tulane University.

Törnqvist and his students based their findings on detailed reconstructions of sea levels in different sections of the delta over the last 8,000 years. Changes in sea level can be caused by melting of the Antarctic or Greenland ice sheets, by vertical movements of the land surface from the weight and compaction of accumulating sediments or by the withdrawal of oil, gas, and groundwater.

Other recent investigations suggest that the basement of the Mississippi Delta is subsiding by about 10 millimeters a year. But Törnqvist's study, which he presented at the annual meeting of the American Association for the Advancement of Science, Feb. 19 in St. Louis, shows subsidence rates of only about 0.6 millimeters per year. Törnqvist's study did not include the basement in the New Orleans metropolitan area, but it did cover an area near Lutcher and Gramercy, Louisiana, only 40 miles west of New Orleans.

If his findings are borne out delta-wide it could have major implications for post-Hurricane Katrina rebuilding plans currently being debated. A stable basement could allow rebuilding in low-lying areas thought to be sinking too rapidly to justify reconstruction.

Törnqvist, who was raised in the Netherlands and received his Ph.D in physical geography from Utrecht University, is hopeful that if he can continue these sea level studies it will be possible to estimate the subsidence rate of the basement underneath New Orleans.

Tulane University, New Orleans, LA 70118 504-865-5000