Mid-Barataria Sediment Diversion: Recent Questions Previously Answered

The Mid-Barataria Sediment Diversion project is an ambitious part of the state’s Comprehensive Master Plan for a Sustainable Coast, designed as a controlled way to reconnect the Mississippi River to the wetlands to the west of the river.

This project broke ground in August 2023, but has since been delayed by a lawsuit from Plaquemines Parish and an apparent change of direction in state support. As such, the diversion has been the topic of recent Senate Transportation, Highways & Public Work Committee meetings on October 11 and November 21. During these hearings, there have been multiple presentations against the current design of the project, and responses in support of the project from various organizations and individuals who urge that the project continue.

Throughout these two committee meetings, there appears to be some misunderstandings of the history of the project, the studies that have been done to support its construction, and even basic ideas of how estuaries and the Mississippi River delta work to provide habitat, land building potential, and bring stability to part of the ever-changing coastal ecosystem.

Many of the questions raised at the last two committee meetings are questions that have been asked, and answered, over the decades as diversions, and then specifically Mid-Barataria Sediment Diversion, have been discussed and planned.

The following will be a sampling of statements made at these committee meetings with background information that will hopefully shed some light on the science that has supported the development of the Mid-Barataria Sediment Diversion.

Science has been the foundation of CPRA’s work and in their development of the Coastal Master Plans, each of which has included plans for the Mid-Barataria Sediment Diversion. It’s this science-based approach that has led to a bi-partisan and unanimous approval of every Coastal Master Plan submitted to the state legislature since 2007.

Science-based decision making can remove the politics from coastal restoration and protection, and sometimes we need reminders that a lot of that science has already been done.

 

Statement: There is a decreasing amount of sediment in the Mississippi River, so there isn’t enough to build the 13,800 acres promised by the Mid-Barataria Sediment Diversion.

Studies: Research, and real-world examples, show that the Mississippi River still carries enough sediment to Louisiana to help build, and maintain, coastal land.

Over the decades, dams and levees have reduced the amount of some types of sediment carried by the Mississippi River. A study in 2009, “Drowning of the Mississippi Delta due to insufficient sediment supply and global sea-level rise,” concluded that there wasn’t enough sediment in the river to prevent further land loss.

A more recent study in 2014, demonstrated that sand carried and stored in the Mississippi River has not decreased since the last dam was installed. The study, “Sand as a stable and sustainable resource for nourishing the Mississippi River delta, stated “We conclude that the lower Mississippi River channel holds a significant reservoir of sand that is available to replenish diminished loads via bed scour and substantially mitigate land loss.”

CPRA’s own research agrees that there is enough sediment in the Mississippi River for sediment diversions to build land.

Real-world examples of the Mississippi River’s ability to carry enough sediment to build land includes the Wax Lake Outlet and Atchafalaya River delta that are estimated to be growing on average 1 square mile a year thanks to just 30 percent of the Mississippi River flow. Along the Mississippi River, the Davis Pond diversion was meant to just introduce freshwater to push back saltwater intrusion, but a study from LSU indicated that in 17 years, the wetlands grew between 1.25 and 3 square miles.

According to the Louisiana Coastal Master Plan, the Mid-Barataria Sediment Diversion could build 21 square miles (26,000 acres) of new land over a 50-year period.

 

Statement: The cost of the Mid-Barataria Sediment Diversion has ballooned from initial estimates, from $1.5 billion in 2016 to $2.9 billion in 2024. The state could be on hook for hundreds of millions of dollars if the cost estimates keep increasing.

Studies: The cost of the Mid-Barataria Sediment Diversion has increased over the years, much like everything else.

Currently, the funding for the Mid-Barataria Sediment Diversion comes from penalties and other payments resulting from the Deepwater Horizon oil spill in 2010, administered by a group of federal and state agencies called the Trustee Implementation Group (TIG). Projects that receive the money are vetted and analyzed to make sure they meet the goal of helping the state coastal area recover from the oil spill damage. To date, the TIG has approved $2.26 billion for the construction of the Mid-Barataria Sediment Diversion and the National Fish and Wildlife Foundation awarded CPRA $660 million towards the diversion project.

Price increases for large, complex projects aren’t unheard of in coastal Louisiana. The Morganza to the Gulf levee system around Terrebonne Parish was authorized in 2007 at $887 million. However, post Hurricane Katrina levee regulations and general costs increases meant that cost went to $6.6 billion today. It is a project that was initially dependent on local funding, but has since received state and federal funding support, despite the large cost increase to reduce flooding risk to more than 200,000 people in the area.

Louisiana is no stranger to the reality that the cost of engineering and building large projects means cost estimates go up as time goes on and the Mid-Barataria Sediment Diversion is no different.

 

Statement: The oil spill money would be better spent in dredging and building coastal wetlands in the shorter term rather than waiting 50 years for the potential to build land.

Studies: The question of efficiency of a sediment diversion vs. dredging sediment from the river to build wetlands is an old one that has been the focus of multiple studies over the years.

Dredging sediment from the Mississippi River or other sources and transporting the sediment to a wetland creation area can provide short term land building benefits. But due to subsidence (natural sinking of the land), sea level rise, and other erosion factors, it can be difficult to stabilize these areas over time. Much like driving a new car off the lot immediately decreases its value, once a dredged marsh is in place, multiple factors start taking its toll on the land.

In contrast, sediment diversions mimic how the pre-levee Mississippi River built land in southeast Louisiana through the periodic high-water events that spread nutrients, freshwater, and sediment far from the river’s main stem. Unlike a built marsh, that once built is still disconnected from the river, a sediment diversion is operated over time to not only build new land, but help sustain dredge-created land as well increasing the lifespan of both.

As outlined in “Mississippi Delta Restoration: The Costs and Sustainability of Ongoing Efforts to Restore and Protect Louisiana’s Coast”, “Marsh creation requires large amounts of fuel for each unit of sediment delivered to a marsh and the costs are subject to changes in energy prices. River diversions, however, use gravitational energy to move sediment and are more sustainable in the long term, especially in an energy-constrained future.”

Dredging to create coastal wetlands is an important feature or Louisiana’s overall coastal protection and restoration strategy as outline in the 2023 Coastal Master Plan with $16 billion envisioned to be spent on marsh creation compared to the $2.7 billion for diversions (page 43). However, sediment diversions are also vital in order to help maintain many of those marsh creation projects long-term.

Although there is a common idea that the Mississippi River flows directly to the Gulf of Mexico without discharging water and sediment into Louisiana marshes, the river has many more “leaks” than most people think. On the east side of the river, there is Neptune Pass flowing at more than 100,000 cfs, with a proposal from the U.S. Army Corps of Engineers to reduce it to 80,000 cfs max flow, Mardi Gras Pass at around 30,000 cfs, the 12-mile long Bohemia Spillway where levees were removed in the 1920s, and a number of canals and crevasses that take Mississippi River water into Louisiana marshes on the eastern side of the river below Bohemia.

 

Statement: The Mid-Barataria Sediment Diversion will destroy the fisheries in the Barataria Basin and along with it the communities and families who live in Plaquemines Parish.

Studies: As Louisiana continues to lose land, shrimpers and oystermen of today are fishing in different areas than their fathers and very different areas than their grandfathers. Cancelling the diversion won’t change that. Building the diversion can, however, help stabilize that land movement over time through land building and pushing back saltwater intrusion.

According to the Environmental Impact Statement (EIS) for the diversion, “Under both the Applicant’s Preferred Alternative and the No Action Alternative, consumers in Louisiana would experience higher prices for locally caught seafood, or would consume additional imported shrimp over time.  However, impacts due to decreased local shrimp availability would occur decades sooner under the Applicant’s Preferred Alternative than under the No Action Alternative.”

In summary, the diversion will have impacts on shrimping quicker than if the project isn’t built, but the same impacts will be arriving either way.

The diversion operation would have impacts to where shrimp and oysters are found as the freshwater pushes back on saltwater and resets the estuary, but it won’t be a wasteland. From the project EIS, “The operation of the MBSD Project is expected to have both beneficial and adverse direct and indirect impacts on fish abundance in the Project area, which would have beneficial impacts on the commercial catch of some targeted species, and adverse impacts on the commercial catch of other targeted species.”

One real-world example is the West Bay Sediment Diversion located on the west bank of the Mississippi River and south of the Mid-Barataria Sediment Diversion location. Built in 2003, this is an uncontrolled diversion (a cut in the natural levee but no ability to control the amount of water that exits into the marsh). The flow rate has varied from -20,550 cfs (reverse flow into the river) to 68,100 cfs, generally following the amount of water flowing down the Mississippi River. In addition to receiving sediment from the river, the proximity to federal river dredging means it has received 56 million cubic yards of material since 2003. A 2022 Operations, Maintenance, and Monitoring report for West Bay Sediment Diversion concludes, “The West Bay diversion project has overall been successful. It is building land and creating extensive wildlife habitat, compared to the open bay prior to project construction.”

Today, the area around Venice and West Bay diversion are lauded as great fishing spots.

 

Statement: Increased flooding will harm communities throughout the area due to the diversion putting more water into Barataria Basin.

Studies: While there will be some increase in water levels in some areas outside the levee system of anywhere to a half foot 1.3 feet, the mitigation measures included in the plan, informed by more than 20 community meetings and other outreach activities, would greatly reduce flooding over time.

According to the Appendix R: Mitigation & Monitoring and Adaptive Management Plans (page 28) of the project’s Environmental Impact Statement EIS, without the diversion, water levels will exceed the local flood threshold in some areas 333 days a year. However, with the diversion, water levels that exceed the local flood threshold is reduced to 1 day a year by 2060 in the communities of Myrtle Grove, Woodpark, Suzie Bayou, Happy Jack, and Grand Bayou.

Essentially, the long-term benefits of the project on flooding in the area greatly exceed projected impacts from the initial project.

 

Statement: It’s not known how a diversion of this size would impact dredging or navigation interests along the Mississippi River.

Studies: The lower Mississippi River is vital to the nation as a major shipping channel, and it is the U.S. Army Corps of Engineers job to make sure that it continues to be open for business. As part of the Mid-Barataria Sediment Diversion EIS Appendix Q: Navigation/Dredging Analysis, the Corps outlines current and past investigations of potential diversion impacts to shoaling, dredging needs, and navigation. In the conclusion of the lengthy look at navigation issues, the Corps found there was not going to be an issue for navigation along the river if the diversion was operated as planned and they recommended to “Continue normal deep-draft vessel navigation following construction of diversion canal.”

 

Senate Transportation, Highways & Public Works Committee Meeting Recordings

You can watch a recording of the Oct. 11, 2024 Senate Transportation, Highways & Public Works Committee here.

You can watch a recording of the Nov. 21, 2024 Senate Transportation, Highways & Public Works Committee here.

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