A new study concludes that the rate of land-building from river diversions in the Mississippi River Delta likely will be dwarfed by the rate of wetland loss.
Scientists studied how fast the Mississippi River Delta grew each year before people inhabited the area and began changing the environment. They then compared that information with observations of how fast the delta is shrinking in modern times. The findings will inform coastal policy and management in this low-lying U.S. region.
The study results, published in the journal Science Advances, used optical dating to measure how fast the delta shoreline migrated seaward under natural conditions.
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"Optical dating determines when sediment grains were deposited by measuring their last exposure to daylight," says Elizabeth Chamberlain of Vanderbilt University, the paper's lead author.
Prior to human influence, the delta grew at a rate of 2 to 3 square miles per year. But over the past century, the rate of land loss in coastal Louisiana has averaged 15 to 20 square miles per year.
Geologist Torbjörn Törnqvist of Tulane University, a co-author of the study, says that given accelerating rates of sea level rise, losses will likely continue long into the future, and that even the best-designed river diversions won't be able to prevent more land loss.
The only viable option, Törnqvist says, is to position river diversions in areas that have the greatest potential to build land and protect the largest population centers, as opposed to placing multiple diversions along the entire shoreline.
Chamberlain and Törnqvist conducted the research with colleagues from Coastal Carolina University, the University of Liverpool in the United Kingdom and Wageningen University in the Netherlands. Additional funding was provided by the Coastal Protection and Restoration Authority of Louisiana.