Putting the Mississippi River Back to Work
ecomagazine.comFeb 1, 2017 — Along the northern Gulf of Mexico coast, few things have had a greater influence on Louisiana and the current dramatic coastal land loss the state faces than the Mississippi River.
Built over thousands of years as the river flipflopped across the landscape looking for the shortest and steepest way to the Gulf of Mexico, south Louisiana’s delta landscape grew and eroded depending on the river’s whim. Levee construction, river shortening, dike fields and other control works began soon after the arrival of European settlers – and through the decades each flood event brought about higher, stronger and wider levees on either side of the river channel.
Along the northern Gulf of Mexico coast, few things have had a greater influence on Louisiana and the current dramatic coastal land loss the state faces than the Mississippi River.
Built over thousands of years as the river flipflopped across the land scape looking for the shortest and steepest way to the Gulf of Mexico, south Louisiana’s delta landscape grew and eroded depending on the river’s whim. Levee construction, river shortening, dike fields and other control works began soon after the arrival of European settlers – and through the decades each flood event brought about higher, stronger and wider levees on either side of the river channel.
These attempts at taming this legendary waterway helped Louisiana and the country grow by limiting floods and making the large-scale water transport of goods possible by connecting the nation’s inland water-way network to the sea. Currently, more than 25% of the nation’s water exports are shipped through Louisiana’s five major ports.
However, that prosperity came at a cost. Levee construction prevents much of the previous marsh-nourishing flooding events while construction of dams and other river control works upstream prevents as much as half of the sediment that used to flow from the Mississippi basin from reaching Louisiana.
Without this additional riverine fresh water and sediment input into the marsh, wetlands in many areas can’t keep up with sea level rise and subsidence. Although there are multiple causes of Louisiana’s land loss, including canal dredging, the unbalanced situation of reduced sediment combined with relative sea level rise has contributed to the loss of about 1,900 sq. mi. of Louisiana’s coast since the 1930s and threatens livelihoods, communities, and commerce. If nothing is done, it’s estimated the state could lose up to an additional 2,250 sq. mi. over the next 50 years.
Although Louisiana had been working for decades to address the land loss and its implications for the state’s residents and economy, including the formation of the Coastal Protection and Restoration Authority (CPRA) in 2005, a collaborative water and coastal research institute was recognized as a need.
In 2011, The Water Institute of the Gulf (the Institute) was formed – with the support of the state of Louisiana, the Baton Rouge Area Foundation, and Sen. Mary Landrieu – to help address technical and research needs for coastal restoration as well as taking the role of a single coordinating group that could bring together larger research efforts.
During the last five years, the Institute has grown and evolved into an organization that integrates social sciences, natural sciences, computer modeling, and data collection while also providing a central place to coordinate work among universities, private companies, non- profit groups, and government agencies.
This inter-disciplinary approach allows the Institute to respond to specific questions about restoration and protection work from local projects up to an ambitious plan to reconnect the Mississippi River to coastal wetlands in strategic areas. These diversions have been included in almost every plan the state has developed over the decades to address land loss, but has remained as just a “good idea” until now, thanks in large part to available funding due to settlements related to the Deepwater Horizon oil spill. These planned sediment diversions are just one tool to benefit a portion of the state’s coastal area, with other projects and strategies planned for areas outside the Mississippi River’s influence.
In simple terms, sediment diversions involve building structures that efficiently capture sediment flowing down the Mississippi River and direct it and the accompanying fresh water into southeast Louisiana coastal marshes previously starved of both. The state built small freshwater diversions in the past as well as uncontrolled diversions by cutting through river levees, but the concept of building an engineered structure specifically targeted to maximize river sediment capture and dispersal is a whole new undertaking. The complexity of the project raises questions about where diversions should be located, how they should be operated, how much land they can potentially build, what the maintenance requirements will be, and how to operate a diversion to minimize disruption to coastal communities and livelihoods.
As the state moves the first planned sediment diversion closer to a 2020 construction start date, the engineering, design, and future operational regime is being informed by numerous research projects from the Institute.
Taking What We Know To Predict The Future
Soon after the Institute was organized, state planners tasked researchers to find answers to two fundamental questions about the forthcoming sediment diversions: 1) where should these large projects be built and 2) how much land could be gained or sustained.
A four-year field measurement program began in 2012 to increase understanding of hydrodynamic and sediment transport processes in the lower Mississippi River. Monitoring stations were set up and boat-based measurements were taken to help provide the information needed for modeling efforts. Research teams led by the Institute’s Mead Allison and partners at the U.S. Army Corps of Engineers looked at multiple sites along the river from the Old River Control Structure south to the river’s Gulf outlets to gather information about water speed and discharge, suspended sediment load in the river, and dynamics of lateral sand bars whose locations and behavior during floods may be critical to siting a diversion.
Institute researchers also collected additional information about marsh vegetation in areas that could be influenced by future Mississippi River sediment diversions as well as several sites in the growing deltas of the Atchafalaya Bay area to the west. Researchers took samples of seven taxonomic groups at over 20 sites across four marsh types in 2014 looking for a variety of factors, including abundance, biomass, and soil nutrient availability throughout the salinity zones while also gathering the previous three years of information from the Coastwide Reference Monitoring System.
“Although time consuming, quantifying above- and below-ground vegetation biomass was a crucial need to address some concerns about what an increase of nutrients with the addition of Mississippi River water could do to wetland soils. These data contribute to a baseline of information prior to diversion operation,” explained Melissa Baustian, Institute coastal ecologist. “Biomass information was also important because it provided the ability to validate the numerical models that calculate vegetation growth based on nutrient availability for each of the taxonomic groups.”
These measurements, along with a number of related data collection programs, helped calibrate a numerical model that integrates hydrology, morphology, water quality, and vegetation changes over time. The model’s foundation started with an open source Delft3D model from Deltares.
The hydrodynamic, morphology, and water quality components were integrated with the Louisiana Vegetation Model developed by the University of Louisiana at Lafayette. This integration captures the feedback among the physical and ecological processes driving the land- scape change.
“The high resolution of the model combined with the ability to have different aspects of the landscape feed back into the equation over time, meaning planners get a much clearer picture of possible project outcomes than has previously been possible,” said Ehab Meselhe, Institute’s director of natural systems modeling.
Using this basin-wide model, the Institute provided CPRA the level of detail they needed to be able to announce in late 2015 a decision to move forward with two of the proposed sediment diversions. Now, this model is being used evaluate and develop new numerical modeling tools for the two selected sediment diversions: 1) an up to 75,000 cfs Mid- Barataria diversion on the west bank of the Mississippi River in Myrtle Grove, Louisiana that is the first one being moved into engineering and design and 2) a 35,000 cfs Mid-Breton diversion on the east bank near Wills Point. For comparison, the Mid-Barataria peak flow will be just a bit shy of the average discharge from the Missouri River while the Mid-Breton’s peak flow will be just shy of the Willamette River in Oregon.
The Institute’s work also considers a number of factors that planners will need to consider after the sediment diversions are built, such as how and when these structures should be operated based on flow and sediment carrying capacity of the Mississippi River. In preparation for this future, the Institute developed a real-time forecasting tool that combines river flow, weather, and coastal conditions that allows for a 7-day hind cast for model validation and a 7-day forecast for potential use during operation.
Additional field work and modeling is now looking at whether a sediment diversion can maintain distributary channels naturally or if the state should budget additional money for periodic maintenance.
You Can’t Manage What You Don’t Measure
Putting large amounts of fresh water, nutrients, and sediment into areas that have been largely cut off from the Mississippi River’s influence for many decades means that these areas will change once operation begins.
Getting a better handle on the scope and types of impacts to be expected from diversions and other restoration pro- jects means knowing what and where to monitor. In response, the Institute designed a comprehensive monitoring program for CPRA that integrates the needed information to note changes in ecology as well as human communities along the coast.
This System Wide Assessment and Monitoring Program (SWAMP) integrates information held in different federal and state government silos and makes recommendations about where additional data needs to be collected. The monitoring system’s design allows for it to operate on a coast-wide and basin-wide scale while also functioning on a much smaller project-level scale if needed to evaluate a specific area.
This “nesting” of smaller-scale monitoring plans within larger-scale plans gives the framework more consistency for data collection regardless of whether the needs are coast wide or down to an individual project. The approach will allow planners to efficiently monitor what drives changes in the system, provide early warnings of change, measure effects of outside conditions like sea level rise, improve the outputs of numerical models, and support better design of future projects.
Traditionally, coastal residents have drawn upon a repository of practices and locally based adaptations in the form of social networks, mobility, and ingenuity to help them cope with and adapt to changing environmental, social, and economic conditions.
“Synthesis of formal technical scientific knowledge integrated with accumulated traditional knowledge and experience can be a helpful approach for developing common understanding and supporting restoration planning to maximize ecological and community resilience,” said Tim Carruthers, director of coastal ecology at the Institute.
A recent report from the Institute, “Trends in oil and gas infrastructure, ecosystem function, and socioeconomic wellbeing in coastal Louisiana,” shows how trends in oil and gas infrastructure and the ecosystem functions of the state’s coast have influenced coastal residents over time.
This report integrates the growth of oil and gas activity and the potential of the coast to support key fish and shell- fish species with the average loss of 16.5 sq. mi of coastal land a year to come up with a socioeconomic wellbeing measure of communities since the 1960s.
“In seeking out locations to live, for example, people have always tried to find the right balance between access to employment opportunities and access to environmental amenities,” said Scott Hemmerling, director of people, resources, and technology at the Institute.
As the landscape changes with fragmenting marshes and increased areas of shallow water, the suitability of the coastal areas for different species changes as does the potential to support important economic and cultural uses of these resources.
Study results show that the wellbeing has remained fairly stable on a coast-wide basis, but there were differences found among regions. It’s unclear why that’s the case, but the report did find correlations between being close (within a 10-minute drive) to high industrial development and within a 30-minute drive of good fishing habitat.
Into The Future
Louisiana’s land loss brings with it a loss of identity, culture, livelihoods, safety, and even entire place names being taken off maps. At least one community is on the road to relocation and many other people continue a slow migration “north” as the Gulf of Mexico get ever closer to their homes.
In 2013, the National Oceanic and Atmospheric Administration removed 31 place names from Louisiana charts. Areas that used to be bays, lakes, or bayous dissolved into open water, permanently erasing them not only for delta habitat, but also for the people who live and work in Louisiana and around the country. There will be more name loses in the next 50 years for Louisiana residents since the rate of sea level rise, climate change, and many other factors leave little doubt that the state will be smaller for the next generation.
However, it’s not hopeless. Researchers are hard at work finding new, more efficient ways to make the wetlands that currently exist more sustainable while improving the ability and cost-effectiveness of building additional land. As part of that effort, The Water Institute of the Gulf will continue to work with state, federal, university, private sector, and NGO partners to help refine a sediment diversion design while continuing with research projects to help inform coastal planners on additional directions for the future.
Soon, that will mean sharing space at the same Water Campus being developed riverside Baton Rouge to encourage more collaboration between partners. The Mississippi River flowing through the front yard of this evolving Water Campus research hub, and the Institute’s future home, will be a constant reminder of the powerful forces that built south Louisiana and the river’s ability to help sustain it into thefuture.
About the Water Institute of the Gulf
Founded in late 2011 through a collaborative effort involving the State of Louisiana, Senator Mary Landrieu, and the Baton Rouge Area Foundation (BRAF), the Water Institute connects academic, public, and private research providers and conducts applied research to serve communities and industry. In 2014, the Institute was selected as the Resources and Ecosystem Sustainability, Tourism Opportunities, and Revived Economy of the Gulf Coast (RESTORE) Act Center of Excellence for Louisiana. In all endeavors, the Institute’s goal is to increase understanding of natural and human aspects of deltaic, coastal, and water systems; to develop tools that apply knowledge to restore coasts and ecosystems; and to reduce risk for people and infrastructure.
The Institute’s technical work includes activities in Louisiana, Latin America, upstream reaches of the Mississippi River, the North Atlantic region, and the Mekong River Delta. To support this work, the Institute has 38 team members whose efforts are supplemented by a number of student interns. The Institute’s full-time research staff of 28 includes 12 with Ph.D.s, one with a J.D., and two professional engineers. An administrative staff of 10 supports these research activities and ensures timely and responsive production of data, tools, reports, and publications to meet the needs of a diverse client base. Learn more at the thewaterinstitute.org.
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