Sediment Diversions: Contrasting Viewpoints in Coastal Restoration

The natural backyard of Lafourche Parish, Photo by Global Green USA  

Louisiana’s 2012 State Master Plan mandates a wide range of restoration techniques. One of the more controversial techniques planned in Southeast Louisiana is sediment diversion. This method involves targeting sediment-rich spots in the Mississippi River and building channels to allow those resources to flow into the degraded wetlands to build new land.

There are a few diversions in full effect, notably the Caernarvon Freshwater Project, which aims to preserve 16,000 acres of marshlands in Breton Sound. The State Master Plan proposes to install ten more river diversions.  While the technique has been praised by the State, some find diversions to be controversial. Fishermen and oyster farmers argue that diversions will decrease salinity and destroy fishing habitats that are vital for coastal economies. Beyond that, communities in the path of a diversion may be forced to move. Finally, some are concerned about the high level of pollutants from the Mississippi River entering the wetlands.

Global Green USA’s interest in diversions comes from a blue carbon perspective: Diversions are intended to create new wetlands where vegetation can be planted to capture and store atmospheric carbon dioxide (CO2). Thus, creating new wetlands not only provides a buffer to coastal communities, but it also helps combat climate change by removing greenhouse gases from the atmosphere and storing it in the ground.

With a methodology for transacting wetland carbon credits recently approved by the American Carbon Registry, the captured carbon can be quantified and sold on the carbon market as a carbon offset. Carbon offsets may provide an economic incentive to landowners wishing to restore their properties—and ultimately enroll in larger-scale carbon markets—as well as help fund larger scale restoration projects, such as diversions, in coastal Louisiana.

A recent event weighed the costs and benefits of river diversions as a restoration technique. At the September 12, 2013 community forum in Lafourche Parish, Bayou Interfaith Shared Community Organizing (BISCO) invited Global Green to present on its Louisiana Wetland Action Program (LWAP).  Additionally, the forum featured presenters who support and who oppose diversions:

  • Support: Bren Haas of the State’s Coastal Protection and Restoration Authority (CPRA) spoke in staunch support of diversions, labeling them a “cornerstone of the 2012 Master Plan.”  While he admitted diversions are experimental, and there is “…still a lot that we don’t know,” he pointed out the increasingly urgent need to implement the Plan. The statistics Haas presented showed a potential loss of 1,750 square miles of the coast by 2060. Out of all the techniques in Louisiana’s restoration toolbox, he sees diversions as the most effective because they both maintain and re-build wetlands. A decaying marsh is refortified when new sediment and nutrients are allowed to enter, encouraging the growth of new vegetation. Mr. Haas argued that sediment diversions successfully counter the land loss resulting from subsidence and sea level rise, and are therefore worth implementing.
  • Opposition: On the other side of the fence was Clint Guidry, President of the Louisiana Shrimp Association and a recognized advocate for fishermen across the Gulf. Mr. Guidry brands diversions as “the flaw in the Master Plan.”  He acknowledged a need for action to counter subsidence, but stated that diversions are: (A) too dependent on a specific river area’s flow at a specific time to control successfully; (B) destabilizing to water quality in areas where fish gravitate to for mating activity; and (C) unlikely to create land that will hold up under increasing storm surges.
  • Qualified Support: Kerry St. Pe, Executive Director of the Barataria Terrebonne National Estuary Program, and a long time coastal advocate, offered support for small, heavily monitored diversions, but dismissed large ones as avenues for floods.  In his eyes, the Mississippi River is “no longer the friend it used to be”: He noted that since 1850, the amount of sediment carried by the river has declined by fifty to eighty percent, making large-scale diversions unnecessary hazards.  Additionally, the natural water/land boundaries we would be striving towards with diversions were shaped before Louisiana was settled, and were altered by the centuries of construction that have enabled people to inhabit the state at all.  

Despite the controversy surrounding diversions, the State’s Coastal Protection and Restoration Authority plans to move forward with the planned projects. The first diversion project that is planned is the Mid-Barataria Sediment Diversion with an implementation date sometime in late 2015.  That diversion will undoubtedly be met with mixed reviews, but exploring both sides of the story is exactly what Global Green roots for: open conversations like BISCO’s community forum which fosters informed viewpoints on the issues affecting our coast and inspires the innovative thinking required to restore it.