Our opinion: For Louisiana's coast, more uncertainty, little time
A new study raises questions about whether one of the most highly touted weapons against coastal erosion will do more harm than good.
At issue are massive river diversions that aim to replenish the sediment and fresh water cut off from coastal wetlands after levees were built to control flooding along the Mississippi and Atchafalaya.
Researchers from Louisiana State University and the University of Maryland released study results last week that indicate such projects, at least as they’ve been envisioned by the state, will destroy more land than they create.
That has already happened with the state’s two major Mississippi River diversions -- Davis Pond in St. Charles Parish and Caernarvon in Plaquemines, the researchers said. They based their findings on a review of satellite images between 1985 and 2015. LSU scientist and study co-author Eugene Turner told The Courier and Daily Comet the diversions did create some land in the immediate area, but that was offset by damage farther away, “and not just a trivial amount.”
The study suggests the state needs to do more research before it moves forward with an estimated $5 billion in river diversions as part of its $50 billion coastal master plan.
“The state is using these models to predict the land gain from a future diversion,” Turner said. “They need to use the existing evidence of what these current ones did and calibrate the model with on-the-ground data.”
All of this has major implications in Terrebonne, as a major component of the master plan would divert sediment and freshwater from the Atchafalaya River into the parish’s western reaches in an effort to bolster eroding wetlands.
Scientists and others involved in the effort to save Louisiana’s coastal communities from inundation have debatedthe issue for years. Other studies, including one conducted by Tulane researchers in 2017, make a strong case that diversions a an effective way to restore the coastal wetlands that are sinking and eroding into the Gulf of Mexico. Other scientists have cautioned that while diversions stand a great chance of working, it’s the way they are builtthat will decide their success or failure.
While scientists sort out the details, the clock is ticking. The master plan says much of Terrebonne and Lafourche will be lost over the next 50-100 years regardless of what is done to save it. Evidence continues to mount that the increased local flooding has already begun. Communities all along Louisiana’s coast face the same threat.
And that means scientists, politicians and others don’t have long to figure this issue out. The state and its coastal communities have long faced the prospect of deciding whether to do something decisive before it’s too late or wait until the science is settled and risk losing everything. The new study is the latest harbinger of the tough choices ahead.
Editorials represent the opinion of this newspaper and not any single individual.