Modeling of Alternative Management Strategies

The Mississippi River is the backbone of south Louisiana’s ecosystem, economy, and culture. It serves as an economical delivery mechanism by which sediment can reach areas that are critically in need of land building and is a key conduit for deep draft navigation to the largest port complex in the United States, serving more than 11,000 deep draft vessels and 450 million tons of cargo each year (Heath et al., 2018).

But it also presents a potential flood risk to communities and infrastructure along its entire length and is occasionally vulnerable as a source of drinking water for the New Orleans Metropolitan Region and much of southeastern Louisiana. The Louisiana Coastal Protection and Restoration Authority (CPRA) has a mission to achieve comprehensive coastal protection and restoration for the state of Louisiana. In doing so, it must engage with the perspectives of a wide variety of stakeholders and decision makers with differing, and sometimes conflicting, interests regarding how the river should be managed and how risks inherent to life near the river should be mitigated.

The goal of the Lowermost Mississippi River Management Program (LMRMP) is to evaluate approaches to water and sediment management that yield practical benefits across all interests.

This report describes implementation of the Lowermost Mississippi River Decision Analysis Framework (LMR-DAF) decision analysis and modeling framework for evaluating and adjusting river management strategies for ecosystem, navigation, and flood management in the Lowermost Mississippi River (LMR).

The LMR-DAF was designed to analyze high-level management strategies that were defined through collaborative discussions with CPRA and stakeholders during earlier phases of LMRMP (Dalyander et al., 2022). The performance of each strategy was then modeled under a wide range of possible environmental forcings for the next 50 years to identify both vulnerabilities in the strategy and the tradeoffs that could be made to address those vulnerabilities.

This report considers three potential strategies: a Business-as-Usual strategy that keeps decision making on the river similar to that of Louisiana’s Master Plan for a Sustainable Coast (CPRA, 2023); a set of Alternate Flow at Old River Control Structure strategies that consider alterations to the flow split between the Mississippi and Atchafalaya rivers; and a set of Alternate Navigation Channel Alignment strategies that consider changing the location at which ship traffic enters the Mississippi River Ship Channel.