Reconnecting the River: How Sediment Diversions Fit into Louisiana’s Coastal Future
It’s no secret that river diversions work. Reconnecting the Mississippi River with nearby wetlands to build and sustain those areas has long been recognized as a key tool in Louisiana’s restoration toolbox, and places like Neptune Pass and the Wax Lake Delta are a testament to the Mississippi River ‘s ability to build land. River diversions have been included in plans to restore the coast for decades, including all of the state’s previous Coastal Master Plans.
The 2029 Coastal Master Plan process has already begun, and the first phase of project submissions ends this Sunday, October 26. Another round is scheduled for mid-2026. However, recent developments at the state level have spelled bad news for sediment diversions. The Mid-Barataria Sediment Diversion and Mid-Breton Sediment Diversion’s cancellations have called the future of these vital, large-scale projects, as well as broader coastal restoration efforts, into question.
Louisiana’s Coastal Master Plan is created using a science-based process that uses computer models to evaluate and predict how projects will perform over the next 50 years to identify the best combination of projects that reduce land loss and risk to coastal communities. The plan is updated every six years to account for progress that’s been made in implementing restoration and protection projects along our coast, changing conditions due to hurricanes or other events, and updated predictions about expected sea level rise and other changing environmental conditions.
The state uses a “Future with Action” model to show all proposed and conceptual projects. A “Future without Action” model shows funded and somewhat permitted projects, but nothing conceptual, or essentially what the coast would look like if no further restoration was done.
River diversions were vital components of every previous Coastal Master Plan due to their ability to build and sustain land over long periods of time. In 2012, the state ran modeling on three scenarios: land loss on the coast with diversions, without diversions and with multiple small diversions. Without diversions, the state would be building 340 square miles less than they could be if they included the projects.
In 2023, three river diversion projects, the Mid-Barataria Sediment Diversion, Mid-Breton Sediment Diversion, and River Reintroduction into Maurepas Swamp, were included in the state’s “Future Without Action” scenario for the first time. This meant that projects included in the 2023 plan were modeled with the assumption that the three diversions would be built. Some projects may have even been modeled to work with Mid-Barataria and Mid-Breton, and without these diversions, those projects may not work as well, work at all or even come to fruition.
2023 Coastal Master Plan – Future Without Action. Land Change from Initial Conditions – Year 50 – Higher Environmental Scenario
The 2029 Master Plan is a reset in many ways. Our coast has been impacted by storms in recent years that drastically changed our coastal landscape. We’ve also made progress in implementing large-scale restoration projects like the Large-Scale Barataria Marsh Creation and Spanish Pass Ridge and Marsh Creation. And, of course, restoration progress has seen setbacks with the Mid-Barataria and Mid-Breton cancellations.
However, formulation of the new plan means that those two sediment diversion projects, along with numerous other restoration projects of differing types that were included in previous plans, from marsh creations to home raising, will be evaluated again to find the best combination of projects that build and sustain land.
Louisiana’s Coastal Master Plan is a world-class process that has made our state a leader in coastal resilience for the last twenty years. Having a science-based plan that minimizes the politics for how we invest in our coast has made Louisiana competitive and led us to securing coastal funds from a variety of sources. Given the limited amount of sediment along our coast that can be dredged, the continued use of the Mississippi River as a source of sediment will be critical for the future of coastal Louisiana.