Latest research finds Neptune Pass is building largest new delta in North America
Study reveals “new sediment hypothesis” that indicates net land building system
NEW ORLEANS – A recent study, by Alex Kolker, Ph.D. and collaborators, revealed that Neptune Pass, located near Buras, La., is building one of the largest new deltas in North America. This study was in-part funded by the National Wildlife Federation who is a coalition member of Restore the Mississippi River Delta.
This study developed a sediment budget for the area and concluded most of the material was recently derived from the Mississippi River, rather than the expansion of the pass, creating a net land building system.
"Neptune Pass is the largest new offshoot of the Mississippi River to form in nearly a century,” said Alex Kolker, Ph.D., associate professor at Louisiana Universities Marine Consortium. “It is building one of the largest new deltas in North America.”
Also involved in this research were Alisha Renfro from the National Wildlife Federation, H. Dallon Weathers the Principal Consultant with hydrographic firm Delta Geo-Marine and Christy Swann, CEO and Founder of the Coastal Adaptation company RCOAST.
Prior to the 2019 high Mississippi River levels, Neptune Pass was a small channel. Between 2019 and 2021, this channel expanded and now carries 15% of the Mississippi River’s flow; more than 100,000 cubic feet per second (cfs) when the river is in flood.
Neptune Pass is currently building one of the largest new deltas in North America in Quarantine Bay. This recent study finds that 56-79% of the sediment material forming the Quarantine Bay Delta is new material from the Mississippi River.
“Between 2019 and 2022, six million cubic yards of sediment from the Mississippi River was diverted through Neptune Pass and deposited into Quarantine and Bay Denesse,” said Alisha Renfro, Ph.D., senior manager for Science Policy for National Wildlife Federation's Gulf of Mexico Program. “This is twice the amount of material used in the nearby Grand Liard marsh creation project that restored 500 acres of wetlands.”
After a few years of relatively low Mississippi River discharge, the river is currently in flood stage and flowing at 1 million cfs. This high flow brings sediments from the river’s enormous drainage basin to Louisiana.
Renfro added, “In the past these high river flows have been major land-building events. Examples are Wax Lake after the 1973 flood and West Bay after the 2011 flood. Once the floodwaters dropped, new land was revealed, and we are likely to see that this year in Quarantine Bay.”
Kolker added, “Our research shows that Neptune Pass is building land in a manner that follows the basic principles of delta geology. These same geological principles also underlie the diversions that are part Louisiana's Coastal Master Plan."
To read the full study, visit https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0320502
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About Restore the Mississippi River Delta:
Restore the Mississippi River Delta is working to protect people, wildlife and jobs by reconnecting the river with its wetlands. As our region faces the crisis of land loss, we offer science-based solutions through a comprehensive approach to restoration. Composed of conservation, policy, science and outreach experts from Environmental Defense Fund, National Audubon Society, the National Wildlife Federation and Pontchartrain Conservancy, we are located in New Orleans and Baton Rouge, Louisiana; Washington, D.C.; and around the United States. Learn more at MississippiRiverDelta.org and connect with us on Facebook and Twitter.