In 1987, John McPhee published an article in the New Yorker entitled Atchafalaya. It described how, for the purposes of commerce, through the construction of levees, the Mississippi River had been confined to the location it had been in since the settlement of Europeans. Defining the path of the river made it possible to establish the Mississippi as a major shipping channel leading far into the interior of the United States, bringing commerce to cities all along the river. The problem with this situation is that the Mississippi at its delta, as it true of other large river systems, is a dynamic system. It will naturally change the location of its outlet at intervals on the order of centuries. By blocking the natural process, humans have caused weird things to happen. Most striking is that the Mississippi as it passes through New Orleans is high above the natural water level of the region. You have to climb up to view the river. We tend to assume that rivers flow through the lowest valleys on their way to the sea, but this is not the case for the Mississippi in Louisiana. McPhee reported that, if it were not for the levees, the Mississippi would have changed course to form an outlet to the Gulf of Mexico through a body of water called Bayou Atchafalaya. Why not just let that happen? The new route would bypass both New Orleans and Baton Rouge, whose economies depend on river traffic.
Another consequence of humans locking the route of the Mississippi in its current place is that sediments carried down the river, which have built up the coast of the region for millennia, are no longer distributed through the coast. Replenishment of river sediments along the coast is one of the reasons Louisiana is losing coastal land at an alarming rate. It has been estimated that Louisiana has lost 4800 square kilometers of costal land since the 1930s. (Other reasons for the loss of coastal lands include increased erosion due to stronger hurricanes hitting the coast, and oil drilling activities that destroy swamp lands.)
After the more than 30 years since McPhee wrote his article, there is finally a plan to try to divert large amounts of sediment from he Mississippi River to eroding parts of the coast in an effort to rebuild what has been lost. Despite decades of coastal erosion, powers-that-be were against making any changes to the current river route. That changed after Hurricane Katrina hit Louisiana in 2005. Suddenly, government officials were willing to take the problem seriously and consider solutions.
If all goes as planned, 2 years from now engineers will punch a massive hole in a nearby levee that holds back the Mississippi River. A 3.5-kilometer-long canal will carry sand and muck from the muddy river into the bay, helping rebuild vast wetlands eroded by sinking land and rising seas. Over 5 decades, researchers forecast that the project—formally known as the Mid-Barataria Sediment Diversion—could move enough sediment to bury the island of Manhattan under 3 meters of muck and create at least 54 square kilometers of new wetlands. The diversion, expected to cost $2 billion, is a critical part of a much larger effort aimed at preventing coastal Louisiana, and the human and wild communities it supports, from slipping beneath the sea.
The plan includes a variety of measures: rebuilding barrier islands with new sand, hauling dredged muck to replenish drowning marshes, strengthening levees and flood barriers, and raising buildings above projected flood levels. But the most novel and ambitious piece is an updated version of Gagliano’s vision of harnessing the Mississippi’s power to build new land. In its latest iteration, the plan calls for creating 11 diversions along the Louisiana coastline. The first and biggest would be the massive mid-Barataria diversion, which would puncture the river’s western bank.
There are lots of uncertainties. Nobody knows for sure if this strategy is going to work. The sediment may pour through so quickly it may cause more erosion than deposition as the sediment makes its way to deep water. Fishermen are worried that pouring large amounts of freshwater into the bay will degrade the environment for fish and other marine life. And the cost is enormous. But it’s a chance to save a unique environmental resource before it disappears forever.
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