Archive for Science
This post originally appeared on Environmental Defense Fund's EDF Voices blog.
By Estelle Robichaux, Environmental Defense Fund
Nine years ago, as Hurricane Katrina gathered strength in the Gulf of Mexico, I called my grandmother and namesake to wish her happy 84th birthday – and to urge her to leave her home on Bayou Lafourche until the storm passed.
It would take several more days before I heard my mother’s voice over the phone and was reassured that everyone in my family was fine. Thankfully, all we lost to Hurricane Katrina were material things.
As we mark another anniversary of the landfall of Hurricane Katrina on August 29, the memory of the infamous storm and its aftermath is still vivid for many current and former Gulf residents.
While New Orleans and many coastal communities have since been revitalized, some scars remain visible and serve as a reminder of the tremendous and destructive power of Mother Nature. They call on us to act now to prepare our communities for the next big storm.
River helps rebuild wetlands
In their most recent reports, the Intergovernmental Panel on Climate Change and the National Climate Assessment warned that as the climate continues to warm, the North Atlantic basin will likely experience more Category 4 and 5 hurricanes.
While the Gulf Coast won’t necessarily see more storms in the future, scientists believe they may be more intense. This, combined with the effects of sea level rise, means the region’s communities and infrastructure will be increasingly vulnerable to storm surge and high winds associated with tropical storms.
At Environmental Defense Fund, we’re working as part of the Mississippi River Delta Restoration Coalition, to rebuild healthy wetlands in coastal Louisiana, using the natural power of the Mississippi River to take advantage of sediment in the river to rebuild land.
In addition to levees and other structural storm protection measures, the state needs resilient coastal wetlands to be part of its hurricane risk reduction system. Coastal wetlands can serve as an important buffer and retention area for storm surge.
That way, when the next big storm shows up, Louisiana communities and cities will be better protected.
Economic stakes are huge
For the last 40 years, EDF has been working to address the root causes of land loss in Louisiana and find innovative solutions to restore the delta. One-quarter of the state's coastal land area has disappeared since 1930 and Louisiana continues to lose land at an alarming rate – one football field every hour, on average.
Coastal restoration will help save jobs and industry vital to our economy, and help us build resilience against catastrophic storm surges like the one brought by Katrina.
It also has direct implications for important national and international economic and ecological systems:
- 100 million birds live in or pass through the delta each year, with 400 different species relying on the delta at some point during their life or migratory cycles.
- Louisiana has the largest commercial fishery in the lower 48 states.
- Five of the 15 largest ports in the country are in Louisiana, and 60 percent of all grain exported from the United States is shipped through the ports of New Orleans and South Louisiana.
- Louisiana is home to the Louisiana Offshore Oil Port, the only deep water oil port in the United States capable of offloading deep draft tankers.
Coming up: Peak hurricane season
With only three named storms to date in 2014, this year’s hurricane season has so far been unusually quiet. But today, nobody in Louisiana is sitting back.
The peak hurricane season, which falls between mid-August and the end of October, has only just begun. This means the Atlantic and Gulf Coasts may see more action soon enough.
At the same time, data show that the intensity and duration of hurricanes continue to increase. Louisianians know we must act now to restore our coast and the protection it gives us before the next Katrina comes along.No Comments
By Erin Greeson (National Audubon Society) and Alisha Renfro (National Wildlife Federation)
While there is no question that large-scale action is urgently needed to add address Louisiana’s land loss crisis, some questions surround the scientific solutions necessary to address this challenge. As the state of Louisiana advances its Coastal Master Plan and the comprehensive set of restoration projects within it, experts have opened discussion to scientists and interested members of the public to provide information, share science and encourage dialogue.
This week in New Orleans, the Expert Panel on Diversion Planning and Implementation had their second meeting, which offered an opportunity to reconvene for updates and discussion on sediment diversions – one of the key tools in Louisiana’s coastal restoration toolbox. In addition to addressing environmental concerns, the panel addressed social and economic questions about river diversions and the communities they will impact.
At the start of the meeting, Mr. King Milling, Chair of the Governor’s Advisory Commission on Coastal Protection, Restoration and Conservation, delivered a powerful reminder of Louisiana’s disappearing coast:
“Demise of this delta would be an environmental impact of international proportions: disaster for economy, culture, communities – all the things we do and live for in the delta. If we don’t proceed urgently, we will lose the delta. Nothing will stop this damage if we don’t proceed in an orderly fashion with large-scale, comprehensive solutions. This is not a time for debate. Our role is to address the issue of remarkable deterioration, and the state’s diversion committee will be addressing issues and conflicts. Its position is to focus on the larger picture of how we can preserve as much as we can, and how can we create a system that will protect as much as we can.”
The first day of the meeting was open to the public, and the agenda reflected many of the areas of focus that require follow-up from the panel’s first meeting. Presentations from the Army Corps of Engineers, The Water Institute of the Gulf and Biedenharn Group focused on the Hydrodynamic Study, which is collecting data in the river and using models to represent conditions in the river as it is today, predicting what the river will be like in the future without diversion projects and how the construction and operation of diversion projects change the river compared to the future without the diversions. They also briefly discussed the Mississippi River Delta Management Study, expected to begin soon, which will focus on the basin-side effects of diversions and evaluate combinations of diversion projects that maximize the number of acres of wetlands built or sustained over time.
Presentations from David Lindquist from the state’s Coastal Protection and Restoration Authority (CPRA) summarized the current state of knowledge on fisheries and wildlife response to existing freshwater diversions. Craig Colten, Ph.D. from the Water Institute of the Gulf highlighted the importance of considering the influences of restoration projects on communities.
A presentation from Micaela Coner and Bob Beduhn narrowed the discussion down to the engineering and design considerations of a single project – the Mid-Barataria Diversion. Ms. Coner, CPRA, discussed the Mid-Barataria sediment diversion project within the context of the 109 Coastal Master Plan projects. Speaking to the plan’s theme of reconnecting the river with its estuaries, she described sediment diversions as the best opportunity to build, maintain and sustain land.
Dr. Robert Twilley, Louisiana State University, described how the river once built natural resource wealth: “Natural resource economies and the flooding of the river once coexisted. The wealth of fisheries, and the wealth of the river building wetlands, once coexisted. Today, there’s a conflict. Historically, the river built land during big flood events. Nature had this figured out. We’re forcing a conflict. There is a resolution to this.”
During the closing portion of the meeting, attendees had opportunities to provide comments to the Expert Panel. Mississippi River Delta Restoration Coalition leaders were among the conversation.
David Muth of the National Wildlife Federation urged the panel to consider the historical context of the river in addressing site-specific questions about diversions: “We have glimpses from historical record about how productive this system once was. But for the past 300 years, we have been choking off that system.”
John Lopez of the Lake Pontchartrain Basin Foundation described the coastal land loss crisis in powerful terms and underscored for a sense of urgency: “This house is on fire. Lives are at risk. We have a great scientific challenge, but we don’t have time to delay.”
More background on the Expert Panel:
During its first meeting in January, the Expert Panel was asked to focus on the topics of uncertainty – underlying natural variability and limitations in knowledge – they perceived surrounding the design and operation of major freshwater and sediment diversions. A report summarizing their findings and recommendations from that first meeting was released in February.
In this report the panel focused on identifying six areas that should be answered or considered as sediment diversions move further from idea into planning, engineering and design:
- Data collection is important for understanding the system as it is today and for evaluating performance of individual diversion projects.
- A controlled sediment diversion does not currently exist, but some information needed to understand the time scales and extent of land building that could be expected from a controlled sediment diversion can be gleaned from natural crevasses.
- The response of plant, fish and wildlife communities to the operation of sediment diversions should be incorporated into modeling of different scenarios, both capacity and operation, of a diversion.
- The potential social and economic influences of a diversion project need to be considered to minimize any potential negative impacts that can be foreseen.
- Planning and design of diversion projects need to be explored under present day and possible future conditions (e.g. sea level rise, changes in precipitation) to maximize project success in the very near and long-term future.
- Communications between planners and stakeholders to discuss the realities and limitations of any predictions is essential for project success.
By Alisha A. Renfro, Ph.D., National Wildlife Federation
As spring weather warms the Midwest, snow melts and drains from 31 states into the Mississippi River. In south Louisiana, the mighty Mississippi River is nearing its peak flow of nearly 900,000 cubic feet of water per second. Rolling down the river with the water is mud and sand, which are essential to building wetlands in the disappearing Mississippi River Delta.
Every hour in Louisiana, a football field of land becomes open water. This land loss crisis is caused in part by levees built for flood protection and navigation which severed the connection between the delta and the river, almost completely halting the land-building processes that once created this iconic landscape.
Sediment diversions are large-scale restoration projects that move sand and mud from the river through the levees into nearby wetlands during high river flows – such as this year’s spring high water flow – to restart the land-building process and help sustain existing wetlands. One important question to understand the full land-building potential of these projects is: Is the Mississippi River a long-term, sustainable source of mud and sand?
A recent Nature Geoscience paper by Jeffrey Nittrouer, Ph.D. of River University and Enrica Viparelli, Ph.D. of the University of South Carolina, “Sand as a stable and sustainable resource for nourishing the Mississippi River delta,” suggests that while the amount of mud carried by the Mississippi River has decreased since the 1970s, the sand it carries has remained steady and may do so for the next 600 years.
The Missouri River is an important source of sediment to the Mississippi, historically supplying about one-half of the total sediment moving down the Mississippi River. However, dams built in the 1950s along the Missouri have been hypothesized as the cause of the large reduction in the amount of total sediment (mud plus sand) that makes its way down to the Mississippi.
In this study, Nittrouer and Viparelli look at changes in the mud and sand carried by the river over a year since the 1970s and found that while the amount of mud that makes it to Tarbert Landing, Miss. (306 miles above the Bird’s Foot delta) has decreased over time, the amount of sand has been consistent. They point out that the likely source of sand is material that is being eroded out of the river channel.
Nittrouer and Enrica applied a model to simulate the response of a sudden reduction in sediment supply that likely occurred with dam construction along the Missouri River in the 1950s. The model indicates that erosion of sand in the river channel between Cairo, Ill. and Vicksburg, Miss. keeps the amount of sand available at Tarbert Landing, Miss. steady for the next 600 years.
Sand and mud are both needed to restore the Mississippi River Delta. Sand, which is 20 percent of the sediment carried by the river, is essential for building new platforms that can support marsh vegetation. Mud, which makes up the other 80 percent, is necessary for maintaining and increasing the resiliency of existing marsh to sea level rise and storm events.
This study suggests that there is a steady supply of sand to the lowermost part of the Mississippi River that can be put to work by constructing and using sediment diversions to mimic nature to build new land, help sustain existing wetlands and begin the restoration of the Mississippi River Delta. This is positive news for large-scale coastal restoration efforts.No Comments
By Estelle Robichaux, Environmental Defense Fund
The Gulf of Mexico Research Initiative (GoMRI) hosted its 2014 Gulf of Mexico Oil Spill and Ecosystem Science Conference January 26-29 in Mobile, Ala. GoMRI was created soon after the 2010 Deepwater Horizon oil disaster when BP committed $500 million over 10 years to fund a broad, independent research program with the purpose of studying the environmental and public health impacts of the oil spill in the Gulf of Mexico.
The conference drew several hundred attendees from academia, state and federal agencies and non-governmental organizations who gathered to hear presentations on cutting-edge research about the impacts of the Gulf oil disaster and continuing socio-ecological recovery. This conference, the second of its kind, facilitates interdisciplinary discussion by giving GoMRI-funded researchers from many different fields an opportunity to come together.
The four-day event entailed around 150 oral presentations in 10 different sessions, more than 400 poster presentations and nearly a dozen other associated meetings, events and plenary sessions. Some of the conference sessions were very technical, including transportation of oil spill residues (i.e., tar balls and tar mats) and dispersants, and impacts of the oil spill on fisheries, coastal marshes and nearshore water ecosystems. Other sessions were technological, focusing on ecosystem monitoring and data management, while others examined the human side, looking at public health and socio-economic issues.
Some of the research coming out of the Coastal Waters Consortium is particularly interesting because it goes beyond the physical and chemical impacts of the spill, focusing on broader ecological issues such as coastal processes and food webs. Dr. Sabrina Taylor is the principle investigator looking at the post-spill reproductive success, survival and dispersal of the Seaside sparrow, a bird that lives its entire life on salt marsh and is very sensitive to environmental changing, making it an excellent “indicator species.”
Dr. Christy Bergeron Burns presented preliminary results showing less species abundance and less reproductive productivity for the Seaside sparrow in oiled versus unoiled areas of Barataria Bay, La. While the trend in abundance was less pronounced in 2013 than it was in 2012, the trends in reproductive indicators (number of nests, failed nests and fledglings) remained consistent. With more data to collect in 2014, this study has not yet reached any final conclusions. But these preliminary results are prompting questions that are shaping the ongoing research to determine the factors that are causing these trends: Has exposure to Polycyclic Aromatic Hydrocarbons or PAHs – compounds found in crude oil – directly impacted the bird’s reproductive success and habitat selection? Is PAH exposure, or environmental stress in general, affecting hormone levels in this species? Or has the primary food source of the birds – insects – been impacted by the spill somehow, indirectly affecting reproductive success and habitat selection of the Seaside sparrow?
After scientifically assessing the correlation of ecological changes to the Deepwater Horizon oil spill, researchers will dig deeper to understand what has actually caused these changes. Continued collection and analysis of data will give the scientific community a clearer, evidence-based picture of how the oil spill affected specific components of the Gulf ecosystem. But the Gulf Coast region will not get the most benefit from this extensive research until scientists have started to develop a more comprehensive, ecosystem-wide understanding of how the oil spill has impacted the Gulf of Mexico.No Comments
This was originally posted by Environmental Defense Fund on EDF Voices.
By Estelle Robichaux, Restoration Project Analyst, Environmental Defense Fund
Soon after my flyover of the Mississippi River Delta, I joined Dr. John Lopez of the Lake Pontchartrain Basin Foundation (LPBF) on a boat ride down the Bohemia Spillway to Mardi Gras Pass. As we sped down the spillway canal, beautiful swamp lilies and purple morning glories popped out against a backdrop of lush, green plants. Once we reached our destination, we saw an incredible number of birds: Laughing Gulls, Snowy Egrets, Great Blue and Tricolored Herons – just to name a few. This, along with an increase in the number of river otters and beavers observed, is a good indicator that there are healthy fish populations in the area.
Thirty-five miles southeast of New Orleans, Mardi Gras Pass is the Mississippi River’s newest and naturally evolving “distributary,” a channel of water that flows away from the main branch of the river. This new distributary began forming during the spring flood of 2011, when the water level of the Mississippi River was so high that it flowed over the natural levee in this area. When the floodwaters receded, Dr. Lopez and his team of scientists noticed two breaches in the embankment. These breaches continued to widen and deepen and soon, right around Mardi Gras Day 2012, the breach was complete. The Mississippi River was once again connected to the surrounding wetlands, allowing freshwater and land-building sediment back into the area.
Louisiana has lost 25% of its coastal land area since 1930 and continues to lose land at an alarming rate – one football field every hour, on average. Man-made levees along the Mississippi River cut off many small distributaries, like Mardi Gras Pass, from the wetlands in the floodplain of the river and have contributed to this massive wetland loss. Our team here at EDF works with partner organizations, including the Lake Pontchartrain Basin Foundation, as part of the Mississippi River Delta Restoration Coalition, which has a vision of reconnecting the Mississippi River to its delta to help protect people, wildlife and jobs in coastal Louisiana.
To address the complex, yet urgent need for coastal restoration in Louisiana, the state legislature unanimously passed the 2012 Coastal Master Plan. This plan is a long-term, science-based restoration program that includes nearly 250 restoration projects such as barrier island restoration, marsh creation, establishment of oyster barrier reefs and sediment diversions that will help rebuild Louisiana’s disappearing coast.
Restoring our coast, restoring my hope
One of the principal guidelines for restoration under the Coastal Master Plan is to address the root causes of land loss by using the natural power of the Mississippi River to build land at a large scale. Sediment diversions, a central component of the plan, embody this principle because they are designed to mimic the natural stages of the river and carry sediment to the areas of coastal Louisiana that need it most. By operating diversions at times of high water flow (like during a flood), large amounts of sediment can be diverted. It will then settle out in the wetlands and shallow bays, eventually building land mass in vulnerable coastal areas.
In a way, Mardi Gras Pass is a naturally occurring ‘pilot project’ of a sediment diversion. Knowledge gained from studying this area can tell us about the land-building properties, as well as the short-term effects, of sediment diversions. To learn more about this, LPBF scientists are studying how the reintroduction of freshwater and sediment to the spillway area is changing the wetlands and affecting wildlife populations.
Swift currents and downed trees along the edge of the flooded forest can make navigating Mardi Gras Pass somewhat treacherous, but we, in a trusty 14’ skiff, maneuvered through the channel and onto the Mississippi River for a brief but thrilling cruise.
This is what it means for the river to be connected to its floodplain, I thought as we emerged out onto the open water, this is what this ecosystem is supposed to be like.
Although I grew up only a few miles from it, this was the third time in my life I had been out on the Mississippi River and the first time it was in a boat small enough that I could reach down and touch its muddy waters. As our tiny boat circled out in that mighty river, despite the heat and the midday sun, I had goose bumps.No Comments
By Alisha A. Renfro, Ph.D., National Wildlife Federation
Last week in Baton Rouge, The Water Institute of the Gulf hosted the inaugural meeting of the Expert Panel on Diversion Planning and Implementation. The panel – comprised of 12 experts in natural and social sciences, engineering and economics – was selected from more than 60 nominees from across the country. Panel members are all from outside Louisiana, in order to foster critical and constructive review of work being led by Louisiana-based experts. Under the direction of The Water Institute of the Gulf and meeting up to three times a year, this independent panel will provide technical review, input and guidance as the state moves forward and refines its plans for diverting fresh water and sediment from the Mississippi and Atchafalaya Rivers to build, maintain and sustain coastal wetlands. For this first meeting, the panel was asked to consider the most suitable approaches to addressing current or perceived uncertainties in the planning and design of sediment diversions.
The first day of this meeting was open to the public and included a series of presentations outlining the urgent need for restoration in coastal Louisiana as well as various perspectives on sediment diversions. Kyle Graham, Deputy Executive Director of the Coastal Protection and Restoration Authority (CPRA), summarized Louisiana’s 2012 Coastal Master Plan. In his presentation, Graham pointed out that there was no single restoration project type that can address the state’s land-loss crisis in one fell swoop, but that a suite of restoration projects are needed, including barrier island restoration, marsh creation, oyster barrier reefs, shoreline protection, hydrologic restoration and sediment diversions. Barrier island restoration and marsh creation can mechanically create land in strategic locations, but sediment diversions convey sediment to not only build new land but also to maintain existing wetlands that would otherwise be lost.
Brigadier General Duke DeLuca, Commander of the U.S Army Corps of Engineers’ Mississippi Valley Division, presented the Corps’ perspective on sediment diversions. DeLuca discussed some of the questions that the Corps would like to see answered as sediment diversions move from plan to implementation. Many of these outstanding questions should be directly addressed through the Mississippi River Hydrodynamic and Delta Management Study, a joint project being conducted by the State of Louisiana and the Corps. The study will use historic and field data, along with models, to do an assessment of large-scale restoration features to address sustainability of the Mississippi River Delta.
Additional presenters included Jim Tripp from Environmental Defense Fund, Michael Massimi from the Barataria-Terrebonne National Estuary Program, Dr. Ehab Mesehle from The Water Institute of the Gulf and Dr. Alaa Ali from South Florida Water Management District.
In a late afternoon panel, Mark Wingate and Martin Mayer of the Corps’ New Orleans District, John Ettinger of the Environmental Protection Agency and Ronnie Paille of U.S. Fish and Wildlife Service, discussed their federal agencies’ views on diversions. Afterwards, the public was given the opportunity to voice their thoughts and concerns about coastal restoration directly to the panel.
The following day, panel members met in private to discuss the uncertainties discussed and the science that needs to be done to address these uncertainties. A report on that meeting will be given at a CPRA meeting in the coming months.
Bold solutions are needed to halt the rate of catastrophic land loss in coastal Louisiana. Every year, communities throughout the coast inch closer to disaster, becoming more and more exposed to the destructive forces of storm events. Infrastructure, which is vitally important to the economy of Louisiana and the nation, becomes more vulnerable, and important habitat for wildlife, fish and birds vanishes.
Limited by money and sediment resources, there is no one type of restoration project that is a cure-all solution. A suite of restoration projects that strengthen and sustain the landscape is necessary. Sediment diversions use the natural power of the river to build new land and help maintain the existing wetlands. To do nothing or to only implement the least challenging types of restoration projects would doom the resource-rich Louisiana coast.No Comments
This was originally posted by Environmental Defense Fund on EDF Voices: People on the Planet.
By David Festa, Vice President, West Coast & Land, Water & Wildlife, Environmental Defense Fund
I was struck by a line in an article in the new issue of Scientific American. It called the loss of Louisiana’s coastal wetlands “the greatest environmental, economic and cultural tragedy on the North American continent.”
It’s easy to see why they would say that. Since the 1930s, efforts to control the Mississippi River and widespread energy development in the delta have resulted in the sacrifice of 1,900 square miles of Louisiana’s coastal wetlands to the sea. If that had happened on the east coast, an area twice the size of Boston, New York City, Philadelphia and Washington, D.C. put together would be under water. Of course, the engineering projects on the Mississippi spurred over a century of economic development and navigation. But the cost has been the loss of the original delta ecosystem, leaving coastal communities more exposed to storm surges and a rising sea level.
As dramatic as that is, the thing that caught my eye even more was another line in the Scientific American article: “Many wetland recovery programs have failed by trying to re-create the original ecosystems.”
The article goes on to make a point that we don’t have to re-create the past to make things better for people and the planet. In fact, when you think clearly and specifically about the need we as a society are trying to meet, and then ask how nature can help meet that need, surprisingly positive things can happen.
Consider Scientific American’s example of the Delaware Bay, an ecosystem that was teeming with aquatic life before settlers built dikes and drained thousands of acres to grow crops.
“Looming on the New Jersey shore of the bay is the Salem nuclear power plant, owned by utility giant PSEG. The plant sucks in billions of gallons of water a day for cooling and kills millions of tiny fish and other creatures as they get drawn through the intake valves. In the early 1990s state regulators asked PSEG to build cooling towers to end the carnage. Reluctant to spend $1 billion to $2 billion, the utility proposed an alternative: restore enough salt marsh to compensate for the loss of fish — more than 10,000 acres.”
The restoration team decided to take a less-is-more approach — cut gaps in the dikes that would let just the right amount of water into the marsh to create an initial maze of tidal creeks, and then let the rest of the creeks develop on their own. “If you engineer a drainage system in great detail, the system is forced to go the way you think it ought to be,” a restoration expert told the publication. “But if you allow it to develop itself, it’s more likely to be stable.”
Today, reports Scientific American, the increase in fish populations more than makes up for the losses from the power plant’s water intake, and the restoration looks like the natural marshes next door. Plus, it saved consumers money because letting nature meet the need cost hundreds of millions of dollars less than the concrete cooling towers.
You see this principle at work in the efforts of EDF and our allies in the Gulf of Mexico. Last year, as part of ongoing efforts to reverse losses in the Mississippi River Delta, Louisiana passed the Comprehensive Master Plan for a Sustainable Coast. This landmark plan serves as the blueprint for restoring Louisiana’s wetlands, and it follows two tenets that proved so successful in the Delaware Bay. First, it focuses on a single goal: rebuilding and sustaining hundreds of square miles of land. Secondly, it relies on nature to do the bulk of the reconstruction. Sediment-laden water from the Mississippi River will be diverted into marshes and shores. Over time, the sediment will create new land and a more resilient coastline.
In the face of extreme weather and global sea-level rise, this new approach takes on great meaning. Superstorm Sandy provided powerful illustrations of how wetlands can serve as a first line of defense against extreme weather events. Salt marsh remnants along Long Island’s Jamaica Bay, for example, helped to protect residents there, while the lack of wetlands around Manhattan left it exposed to crashing waves.
More than 3 billion souls — 40 percent of the world's population — live as close to the sea as New Orleans. By letting nature back into the game, we can help rebuild coastal Louisiana and turn “a North American tragedy” into a model of success for protecting nearly half the planet’s population.
New study looks at groundwater transport flows and their effects on estuaries in the Mississippi River DeltaDecember 13, 2013 | Posted by Delta Dispatches in Science
By Alisha A. Renfro, Coastal Scientist, National Wildlife Federation
Estuaries are some of the productive – and in many ways, some of the most complex – ecosystems in the world. The abundance and distribution of fish and wildlife within an estuary largely depends on the amount, location and frequency of freshwater inflow. The construction of flood control levees along the lower Mississippi River has severely constricted the surface freshwater flow into the surrounding basins. However, a new study published in the Journal of Hydrology, “Pathways and processes associated with the transport of groundwater in deltaic systems,” led by Alex Kolker, Ph.D., suggests that additional fresh water from the Mississippi River is introduced into these estuaries as submarine groundwater discharge through sandy paleochannels buried beneath the muddy delta surface. These findings may have important implications for the ecology of the estuaries adjacent to the Mississippi River as well as coastal restoration projects in the Mississippi River Delta.
Submarine groundwater discharge refers to the release of groundwater directly into marine waters. Much like rivers, submarine groundwater delivers fresh water, nutrients and metals to coastal waters. However, it is often invisible, as the water seeps through permeable sediments, rather than moving through confined channels on the earth’s surface. In the study, the researchers investigated several different lines of evidence to determine if submarine groundwater flux from the Mississippi River was a significant source of fresh water to Barataria Bay, a basin adjacent to the west bank of the river.
The researchers found that there were localized sources of fresh groundwater into the bay and the flux of groundwater varied over time. Investigation into the unseen geology of the bay indicated that the input of submarine groundwater into Barataria Bay was associated with more permeable sandy sediments that were remnants of distributary channels and other sandy deposits built prior to the leveeing of the river system. The results also suggest that the variable nature of the submarine freshwater discharge into the bay is linked to river stage, where high water levels in the river are associated with increased groundwater flow. Overall, the study evidence suggests that while the flux of groundwater into Barataria Bay may be limited by river stage and the presence of sandy paleochannels, submarine groundwater was a major source of freshwater into the bay, with results suggesting fresh groundwater flux exceeds the limited surface water inputs.
The importance of submarine groundwater as a freshwater source in the delta may have very important implications for the ecology of the estuaries adjacent to the river. The transitional environments between freshwater and saltwater, estuaries – influenced by a combination of freshwater flow, rainfall, tides, winds, waves and storm events – are some of the most dynamic ecosystems on earth. This is undeniably the case in the Mississippi River Delta, where estuarine conditions vary day to day, week to week and year to year. In addition to these factors that drive estuarine conditions throughout the world, the Mississippi River Delta’s estuaries are also affected by devastating wetland loss and encroaching salt water from the Gulf of Mexico which, when combined with the severely limited freshwater inputs, has shifted the abundance and distribution of the assortment of fish and wildlife that depend on the estuary.1 Comment
Basics of the Basin research symposium discusses past, present and future of the Pontchartrain BasinNovember 6, 2013 | Posted by Delta Dispatches in Mardi Gras Pass, Meetings/Events, Mississippi River Gulf Outlet, Science
By Shannon Hood and Estelle S. Robichaux, Environmental Defense Fund
On October 24-25, 2013, the Lake Pontchartrain Basin Foundation (LPBF) hosted its 11th Basics of the Basin research symposium. Scientists and researchers from academia, non-profit organizations, private consulting groups and federal and state agencies gathered at the University of New Orleans (UNO) on the shores of Lake Pontchartrain to discuss the past, present and future issues of the Pontchartrain Basin. LPBF has hosted these biennial symposiums since 1992, providing an opportunity for students and established researchers alike to share and discuss the most up-to-date research on the restoration and management of Louisiana’s Pontchartrain Basin.
After opening remarks by Dr. John Lopez, executive director of LPBF, the plenary continued with comments and presentations from Phil Turnipseed of the U.S. Geological Survey; Dr. Ioannis Georgiou, Director of the Pontchartrain Institute for Environmental Sciences at UNO; and Dr. Chip Groat, President and CEO of The Water Institute of the Gulf, among others. The conference was grouped into seven general session topics, including hydrodynamic modeling, water quality, storm surge protection, river diversions, wetland restoration, the Central Wetlands Unit and fisheries. Because of the diversity of environmental concerns within the Pontchartrain Basin, broad, interdisciplinary research is essential to effective system-wide restoration and management.
Understanding the present condition of the Lake Pontchartrain Basin requires a look into the history of the lake itself. Dr. Oliver Houck, professor at the Tulane University Law School, provided the storied account of the history of Lake Pontchartrain during his keynote speech. He spoke of the lake’s days as a hot spot for recreation, as well as its decline during the years when the lake was dredged for the clam shells that lined the bottom. This dredging caused a rapid decline in the health and suitability of this lake for wildlife habitat and for recreation. A few brave souls recognized the trauma that the lake was enduring and took on the task of halting the dredging to allow the lake to begin to heal. Through years of dedication, lawsuits and creative thinking, the dredging was successfully stopped, and the healing process began.
Lake Pontchartrain Basin Foundation’s original research was well represented at the conference, with 14 presentations in six different sessions. Eva Hillman presented LBPF’s research into the salinity levels found within wetland soils in the Central Wetlands Unit (CWU), just west of New Orleans. Construction of the nearby Mississippi River Gulf Outlet (MRGO) in 1968 allowed salt water to easily enter these previously freshwater wetlands and lead to severe deterioration of the CWU wetlands. Although the MRGO has been closed since 2009, much of the area still remains highly degraded. LPBF scientists are monitoring soil salinity throughout the CWU to inform restoration efforts, specifically re-vegetation projects.
Research conducted by LPBF scientists on Mardi Gras Pass, a new and evolving distributary of the Mississippi River, was also on display. Dr. Theryn Henkel presented preliminary research on where the fresh water and sediment from Mardi Gras Pass is going once it enters the receiving basin. Results from this study indicate that the deposition of sediment happens well before the influence of fresh water on salinity levels in the receiving basin is no longer observed, and that sediment travels further into the northern areas of the basin than it does to the south. Andreas Moshogianis presented the preliminary findings of ongoing biological assessments in Mardi Gras Pass, most notably that a range of both fresh- and saltwater fishes have been caught during these assessments, often in the same net. LPBF’s research on Mardi Gras Pass is important because it has implications for future restoration efforts throughout coastal Louisiana, as scientists and citizens work to reconnect the Mississippi River with its delta.No Comments
By Alisha Renfro, Coastal Scientist, National Wildlife Federation
The Mississippi River is one of the most managed river systems in the world. However, that management has focused on navigation and flood control needs to the detriment of the economically and ecologically important coastal Louisiana landscape. This week, the U.S. Army Corps of Engineers and Louisiana’s Coastal Protection and Restoration Authority (CPRA) hosted a public meeting in New Orleans to present information and preliminary results of their joint effort on the Mississippi River Hydrodynamic and Delta Management Study. This large-scale, long-term study is developing tools to evaluate different combinations of restoration projects in an effort to address the long-term sustainability of the Mississippi River and its delta while balancing the needs of navigation, flood protection and restoration.
The scope of the study extends from Vicksburg, Miss. south to the Bird’s Foot delta. The study is actually comprised of two coupled, but somewhat distinct, efforts. The hydrodynamic portion of the study will focus on characterizing the dynamics in the river and developing models that can be used to evaluate river-side changes due to proposed freshwater and sediment diversion projects. It will also inform location and design of these projects to maximize their effectiveness and minimize the potential for shoaling in the river’s navigation channel. The delta management part of the study will focus on the basin-side benefits and changes caused by these restoration projects. The delta management portion of the study has not yet begun. Currently, the state of Louisiana and the Army Corps are working to define the depth and breadth of that part of the study.
The afternoon session of the meeting focused on detailed technical presentations on the study. The different tasks of the Mississippi River Hydrodynamic and Delta Management Study include a geomorphic assessment, data collection and an extensive modeling effort. The geomorphic assessment focuses on compiling historical river data, dredging records and satellite imagery to document the historical trends in the river. The data collection effort will compile existing data and conduct field work to fill in gaps in understanding of the water and sediment dynamics that currently exist in the river. The historical data and present data will be integrated into the modeling work to inform the models and to ensure that the models capture the dynamics of the river system. The modeling effort includes a suite of models that each has different strengths and weaknesses. These models will be used to forecast the large-scale, long-term and shorter-term regional changes expected in the river in both a future without river diversions and a future that includes different combinations of diversion projects.
The presentations from the technical meeting indicate that this collaborative state of Louisiana and Army Corps effort has moved forward significantly since it began. The geomorphic assessment has been completed and a final report on its results is expected by the end of this year. The data collection effort is ongoing, having captured the low discharge of the river last year and the higher flow discharge from this past spring. Many of the preliminary model simulations have begun, and the preliminary results presented at this meeting emphasized the dynamic nature of the Mississippi River system, where water discharge, sediment transport and deposition can not only vary greatly from year to year, but also from week to week. The preliminary results also point to the importance of appropriate size, location and operation of sediment diversions in order to maximize sediment conveyance into adjacent wetlands and to reduce potential riverside impacts.
The Mississippi River has been a key feature in the growth and development of the U.S. However, for more than 80 years, the management of the river has focused on balancing the needs of navigation and flood control. A shift away from that management scheme towards one that balances navigation, flood control and restoration is absolutely critical for the survival of the delta ecosystem and, ultimately, the communities and navigation industry that depend on the Mississippi River Delta. The Hydrodynamic and Delta Management study is poised to be the effort that changes the way we think about management of the river and how we build a more sustainable, holistic system for our future.No Comments