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NASA looks at Louisiana delta system, eyes global forecasts

by Mary Sewell

MIKE ISLAND, La. — Erosion, sinking land, and sea rise from climate change have killed the Louisiana woods where a 41-year-old Native American chief played as a child. Not far away in the Mississippi River delta system, middle-school students can stand on islands that emerged the year they were born.

NASA is using high-tech airborne systems and boats and mud-slogging work on islands for a $15 million, five-year study of these adjacent areas of Louisiana. One is hitched to a river and growing; the other is disconnected and dying.

Scientists from NASA and a half-dozen universities from Boston to California aim to create computer models that can be used with satellite data to let countries worldwide learn which parts of their dwindling deltas can be shored up and which are past hope.

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“If you have to choose between saving an area and losing another instead of losing everything, you want to know where to put your resources to work to save the livelihood of all the people who live there,” said lead scientist Marc Simard of NASA’s Jet Propulsion Laboratory.

While oceans rise because of climate change, the world’s river deltas — home to seafood nurseries and more than 300 million people — are sinking and shrinking.

To figure out where to shore up dying deltas, NASA is studying water flowing in and out of Louisiana’s Atchafalaya and Terrebonne basins, sediment carried by it, and plants that can slow the flow trap sediment and pull carbon from the air.

Louisiana holds 40% of the nation’s wetlands, but they’re disappearing fast — about 2,000 square miles (5,180 square kilometers) of the state have been lost since the 1930s. That’s about 80% of the nation’s wetland losses, according to the U.S. Geological Survey.

Using two kinds of radar and a spectrometer that measures more colors than the human eye can distinguish, high-altitude NASA airplanes have been collecting information such as water height, slope, sediment, and the types and density of plants. Some measurements are as precise as a couple of centimeters (less than an inch).

On boats and islands, scientists and students from across the country take samples and measure everything from currents to diameters of trees. Their findings will be used to calibrate the airborne instruments.

“I’ve been working here 15 years, and one of the toughest parts about working in a delta is you can only touch one little piece of it at any one time and understand one little piece of it at one time,” said Robert Twilley, a professor of oceanography and coastal sciences at Louisiana State University. “Now we have the capability of working with NASA to understand the entire delta.”

The Mississippi River drains 41% of the continental United States, collecting 150 million tons (130 million metric tons) of sediment per year. But, mainly because of flood-prevention levees, most sediment shoots into the Gulf of Mexico rather than settling in wetlands.

“Deltas are the babies of the geological timescale. They are very young and fragile, in a delicate balance of sinking and growing,” NASA states on the Delta-X project website.

In geological time, young means thousands of years. On that scale, Louisiana’s Wax Lake Delta is taking its first breaths. It dated to 1942 when the Army Corps of Engineers dug an outlet from the lake to reduce flood threats to Morgan City, about 20 miles (32 kilometers) away. Sediment from the Atchafalaya River filled the lake, then began creating islands in the Gulf.

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