Archive for Science
By Shannon Cunniff, Deputy Director for Water, Environmental Defense Fund
Coastal zones are the most densely populated areas in the world. In the U.S., they generate more than 42 percent of the nation’s total economic output. These coastal communities, cities and infrastructure are becoming increasingly vulnerable to the effects of climate change. Rising seas and increased storms, as well as ongoing coastal development, have stripped these natural environments of their innate resilience to storms and flooding, leaving coastlines and the people who live there especially exposed.
Protecting coastal areas requires a multipronged approach. Traditional hardened infrastructure, such as levees and floodwalls, should be combined with natural infrastructure, such as dunes and barrier islands, to optimize storm protection. By attenuating wave energy, natural infrastructure measures can enhance the performance of and complement traditional gray infrastructure. And in certain situations, natural coastal infrastructure measures can reverse coastal erosion, help rebuild shorelines and even keep pace with rising sea levels.
Natural coastal infrastructure measures also provide significant co-benefits to communities. In addition to reducing the effects of storm waves and surge, these wetlands and other plant-based means also improve water quality, enhance recreational and commercial fisheries, add to the coastal esthetic and attract tourists. Their installation or restoration can also buy time for communities as they develop long-term strategic plans to cope with sea level rise.
In Louisiana, coastal planners understand the importance of nature-based designs, such as sediment diversions and barrier beach nourishment, when developing coastal restoration and protection plans – the state’s Coastal Master Plan is a combination of restoration, protection and resiliency projects.
But with their myriad of benefits, why aren’t natural infrastructure measures being implemented to a greater degree in other parts of the nation?
In part, the reason is the lack of accepted engineering design guidance – a document that explains the engineering principles, issues, methods, and performance metrics for evaluating, siting and designing features. Lacking such, engineers cannot formally sign off on the designs and risk benefits that will be realized.
How can we quantify the storm risk reduction benefits of nature-based measures, so as to help decision-makers and planners choose the best methods for their needs and find financing to implement these projects? Can we accelerate development of engineering guidance?
Natural Infrastructure Workshop and Report
Seeking to answer these questions, Environmental Defense Fund (EDF) convened a workshop of 19 coastal engineers, scientists, program managers, and financiers to discuss establishing storm risk reduction performance measures of various natural coastal infrastructure solutions.
After completion, EDF produced the report, “Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features,” which reviews the state of knowledge on the risk reduction performance of natural and nature-based infrastructure, compiled from existing literature as well as workshop participant input. The report includes findings on a host of nature-based measures, including beach nourishment, vegetated dunes, barrier island restoration, edging and sills (living shorelines), oyster reefs, coral reefs, mangroves, maritime forests and coastal wetlands (non-mangroves).
While the report is a bit technical, the authors hope that city planners, coastal engineers and other decision-makers find it useful when determining which storm protection measures to implement in their communities.
For each of the measures, the report summarizes its storm risk reduction attributes (e.g., wave attenuation and storm surge protection); lists its strengths, known weaknesses and uncertainties about utility for risk reduction; and identifies suitable conditions for implementation. The report also indicates where engineering design guidelines already exist (e.g., for beach nourishment and dune building) and whether they can be created by modifying existing guidelines (e.g., oyster and coral reefs function like submerged breakwaters).
For the layperson, Table 1 is a one stop shop for information on how each storm risk reduction measure stacks up next to other methods. The table is a summary of the strategies – natural, nature-based, as well as structural – and how each compares regarding risk reduction performance, costs, climate change mitigation, and adaptability to seal level rise and changing community needs.
To guide further research supporting adoption of natural infrastructure into coastal resilience plans, the report provides the most catalytic and pressing research needs and lists other survey needs gathered from the literature or raised during the workgroup discussion.
Workshop participants – and subsequent consultation with other engineering experts – confirm that there is sufficient confidence in the ability of natural coastal infrastructure measures to reduce impacts of storms and sea level rise to coastal communities, such that these approaches should be routinely considered as viable options by decision-makers.
With what we know now, implementation of these approaches can be facilitated by developing detailed engineering guidelines that provide functional and structural design guidance as well as address other design issues. As projects are built and monitored, we can further expand knowledge of the circumstances where these measures work best; learn more about how traditional structural, nonstructural, natural infrastructure and nature-based measures can optimally work together; understand how coastal processes are effected; and track the measures’ life expectancies in our increasingly dynamic coastal environments.
You can show your support for coastal restoration by taking the pledge to urge leaders to be a powerful voice for coastal restoration. Take the pledge at RestoretheCoast.org!No Comments
By Estelle Robichaux, Restoration Project Analyst, Environmental Defense Fund and Gaby Garcia, Science Intern, Environmental Defense Fund
By the early 1990s, Louisiana’s coastal land loss crisis had been studied and documented for more than two decades. Successful establishment of the state-level Office of Coastal Restoration and Management and the Wetlands Trust Fund in 1989 galvanized support and action for wetlands restoration at the federal-level as well. In 1990, Louisiana U.S. Senator John Breaux co-sponsored and helped pass the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA), sometimes called the “Breaux Act.”
The Act was one of the first attempts to support a comprehensive approach to restoring Louisiana’s coastal wetlands by establishing a dependable, long-term funding stream for projects. A new federal interagency task force, made up of five federal agencies and the Louisiana state government, was also created by the Act to oversee coastal restoration activities, including the prioritization, planning and implementation of small- to medium-scale projects.
Three years after CWPPRA was enacted, in 1993, the Task Force published their Louisiana Coastal Wetlands Restoration Plan, which recommended changes in management of the lower Mississippi and Atchafalaya Rivers. The plan focused specifically on increasing the sediment and freshwater supply to coastal wetlands to reestablish natural land-building processes.
The CWPPRA plan only has a 20-year time horizon, as opposed the 50-year perspective taken in other contemporary plans published by the Louisiana Governor’s Office of Coastal Activities, the Louisiana Department of Natural Resources (LDNR), Louisiana State University or the 2012 Coastal Master Plan. Despite the shorter outlook of the CWPPRA plan, it relies on similar principles and strategies we see in these other plans. Namely, this plan calls for:
- Shifting navigational use from the existing bird's foot delta to a new western delta in a neighboring estuary, possibly Breton Sound;
- Multiple diversions to address land loss in Barataria Basin;
- Reactivation of old distributary channels;
- Seasonal changes in the Atchafalaya River’s flow distribution; and
- Projects to facilitate hydrologic restoration, such as: Nourishing barrier island chains and Controlling tidal flows in large navigation channels.
Small scale tests, important success
Even before the passage of CWPPRA, the LDNR was implementing small-scale diversions by cutting crevasses into banks of the southernmost reach of the Mississippi River. Between 1986 and 1993, 20 crevasses were constructed with a mean discharge rate of less than 4,000 cubic feet per second (cfs). Despite the lower flow rates, these crevasses created nearly 1,400 acres of emergent marsh during this period, an impressive amount of land considering the scale of these projects.
The early results of these experimental projects encouraged the prioritization of sediment diversions in the CWPPRA planning process, many of which have also performed well. The Channel Armor Gap Crevasse, for instance, was constructed in 1997 in one of the most rapidly subsiding areas of the delta. This crevasse created nearly 200 acres of land over 10 years and increased overall sediment elevation by more than three feet.
The West Bay Sediment Diversion, on the other hand, was constructed in 2003 and had formed little subaerial land despite the creation of two small spoil islands in the bay in 2009. Due to this lack of land building, it was considered a complete failure and was in the process of being deauthorized. But after the historic flood of 2011, which delivered large quantities of sediment to coastal Louisiana, dry land had emerged in West Bay by that fall. This combination of spoil islands and pulsing floodwaters has proven successful in building land here and may be translated elsewhere across the coast.
Scaling up the vision for restoration
CWPPRA has played an important role in funding restoration projects, beyond diversions, across the coast. The program has also been critical in supporting long-term, large-scale undertakings, such as the Coast-wide Reference Monitoring System and planning efforts like the Barrier Island Shoreline Feasibility Study and Coast 2050.
The Barrier Island Shoreline Feasibility Study was the first large-scale feasibility study sponsored through CWPPRA. The technical analysis, completed in 1997, was designed to figure out the most effective barrier island configurations to protect inland areas from saltwater intrusion, wind and wave action, storm surge and other extreme events, such as oil spills. An estimate of the possible quantitative effects of different regional barrier island arrangements on Louisiana’s environmental and economic resources were produced through this work as well.
The scope of the study was limited to the shoreline from the Atchafalaya River east to the Mississippi River and provided two alternatives for restoration. These results ultimately informed the initial Barrier Shoreline Restoration studies conducted as part of the Army Corps’ Louisiana Coastal Area (LCA) Ecosystem Restoration Study, which in turn formed the basis for two of our priority projects, Barataria Pass to Sandy Point and Belle Pass to Caminada Pass Barrier Island Restoration.
While the CWPPRA Plan proposed some forward-thinking solutions at the basin-wide level to mimic natural processes, Coast 2050 took comprehensive planning even further. This initiative, finalized in 1998, was jointly developed by the Louisiana State Wetlands Authority and the CWPRRA Task Force and takes a regional perspective on restoration strategies for long-term ecosystem sustainability. The LCA Ecosystem Restoration Study was largely based on the recommendations and vision of Coast 2050, both of which played a significant part in shaping the 2012 Coastal Master Plan and the way we envision restoration in coastal Louisiana.
Be sure to check out our next post for more details on Coast 2050 and the Louisiana Coastal Area Study!
You can show your support for coastal restoration by taking the pledge to urge leaders to be a powerful voice for coastal restoration. Take the pledge at RestoretheCoast.org!No Comments
By Estelle Robichaux, Restoration Project Analyst, Environmental Defense Fund and Gaby Garcia, Science Intern, Environmental Defense Fund
This post is part of a series on early restoration planning in Louisiana. Be sure to check out part one for a look back to 1973.
In 1988, the Coalition to Restoration Coastal Louisiana (CRCL) released a plan titled Coastal Louisiana: Here today and gone tomorrow? The plan, which was a joint effort by stakeholders and scientists, focuses on the Mississippi River Delta region and is framed as a citizens program for protecting Louisiana’s environment, economy and heritage.
The plan provides nearly 20 recommendations, including a restoration action program, suggestions for how to finance the program, as well as specific institutional and legislative recommendations designed to galvanize restoration.
Among the most notable elements is the assertion that sediment diversions would be the most beneficial method of wetland restoration and that several of them should be constructed along the Mississippi and Atchafalaya Rivers. This was also one of the first plans to advise against any new levee construction.
Many of the plan’s most significant propositions, those focused on restoration action, have yet to be realized, though the science behind sediment diversions is well developed and we continue to advocate for them as a sustainable restoration tool.
A bold but realistic plan of action
CRCL’s plan has two specific resource goals that are still strongly advocated for:
- To utilize freshwater and sediment diversions along the Mississippi River and Atchafalaya Rivers to sustain and restore coastal wetlands;
- To beneficially use dredged material from channel maintenance and existing spoil banks to backfill canals and nourish created wetlands and barrier islands
Restoring natural processes: Mississippi River water & sediment diversions
The Caernarvon and Davis Pond diversions were still being designed at the time this plan was published. Although there were expectations these structures would help control saltwater intrusion and reduce wetland loss, the plan underscores their limitations in active wetland restoration and land building. Despite the fact these diversions were designed for salinity and flood control, both areas have seen new land growth, though not at the scale or rate anticipated for sediment diversions.
The action program calls for the construction of a suite of freshwater and sediment diversions to restore hydrologic connections and halt wetland loss. The essence of many of these restoration ideas can be found in Louisiana’s 2012 Coastal Master Plan (CMP). Some of the restoration actions proposed in the 1988 plan include:
- One or two diversions from the Atchafalaya River into the Lake Verret Basin and Western Terrebonne marshes.
- 2012 CMP: Two diversions from the Atchafalaya will increase freshwater and sediment flows into Terrebonne marshes from Bayou Penchant westward, including our of our coalition’s 19 priority projects, Increase Atchafalaya Flow into Terrebonne Marshes.
- Restoration of Bayou Lafourche into a distributary of the Mississippi River, with a diversion into Timbalier Bay.
- 2012 CMP: Small-scale freshwater diversion from the river into Bayou Lafourche.
- Freshwater and sediment diversions, at Bayou Manchac and Blind River, to bring Mississippi River water into the degraded swamps south of Lake Maurepas.
- 2012 CMP: Two freshwater diversions, at Blind River and Hope Canal, and hydrologic restoration of the Amite River to restore freshwater inputs to Lake Maurepas, including one of our priority projects, West Maurepas Diversions.
- A large-scale sediment diversion of the Mississippi River below New Orleans into Barataria Basin and a navigation channel from the river into Breton Sound in the vicinity of Empire.
- 2012 CMP: Two sediment diversions into Barataria Basin in the vicinity of Diamond and Myrtle Grove, Lower and Mid-Barataria Sediment Diversions (also two of our coalition’s priority projects).
Beneficial use of dredged material
In addition to the focus on restoring natural processes by using freshwater and sediment diversions, the plan has another major component that concentrate on restoration actions that would provide short-term benefits as well as some regulatory changes. This component focuses on using dredged sediments, taken from the bottoms of canals or by removing spoil banks, for restoration efforts.
It is recommended that all dredged material from channel maintenance work should be used for wetland creation and restoration. Sediment from spoil banks would be used to plug many of the abandoned canals along the coast, which would also provide hydrologic restoration of freshwater flow across the affected marshes.
Looking back, moving forward
As we review these early restoration plans, it becomes clear that using water and sediment from the Mississippi River to restore Louisiana’s coastal wetlands is not a new idea. Diversions have long been a key component in coastal restoration planning, though they are only one of the suite of tools we can use.
Restoration planning has spanned more than four decades in Louisiana, but it is only in the last two that consistent funding became available. Check out our next post for more on funded restoration programs in Louisiana.No Comments
FOR IMMEDIATE RELEASE
Samantha Carter, National Wildlife Federation, 504.264.6831, email@example.com
Emily Guidry Schatzel, National Wildlife Federation, 225.253.9781, firstname.lastname@example.org
Raleigh Hoke, Gulf Restoration Network, 573.795.1916, email@example.com
A Resilient, Sustainable New Orleans
A Decade after Katrina, Groups Issue Recommendations for Community Protection, Restoration
(New Orleans – August 11, 2015) To commemorate the upcoming 10th anniversary of Hurricane Katrina, a coalition of local community and conservation advocacy groups working to restore wetlands around the Mississippi River Gulf Outlet (MRGO) released a new report today.
The MRGO Must Go Coalition’s report – titled "10th Anniversary of Katrina: Making New Orleans a Sustainable Delta City for the Next Century" – reflects on the progress that has been made since Hurricane Katrina and offers recommendations for ensuring the full protection and long-term resiliency of the Greater New Orleans communities, including implementing a “Multiple Lines of Defense Strategy” to protect coastal communities and wetland habitat.
In conjunction with the report release, members of the MRGO Must Go Coalition released the following statement today:
“Hurricane Katrina brought to the forefront the dire need to improve the resilience of New Orleans and its coastal neighbors. Katrina barreled onshore, churned through MRGO, and wreaked havoc in the Greater New Orleans area – showing us that levees alone are not enough to protect our people, natural resources and economy.
“Today, our coastline continues to disappear at the alarming rate of a football field every hour. As coastal wetlands wash away, with them go our natural defenses. Healthy wetlands and barrier islands serve as natural buffers, defending us against storms. Without slowing down this land loss crisis, we will continue to be vulnerable to storms, sea level rise and the growing risks of climate change.
“Ten years later, we have made great strides toward both restoration and protection. The closure of MRGO, the passing of the 2012 Louisiana Coastal Master Plan, the adoption of an Urban Water Plan and major upgrades to structural protections like levees and storm surge barriers are all true marks of progress for our region.
“However, the critical work to achieve protection and resiliency is really just beginning. We must continue to implement a Multiple Lines of Defense Strategy against storms – including community level planning and preparedness, urban storm water management, and protecting and restoring our coastal wetlands. We must build on the momentum of the last decade and continue to work to make New Orleans a model city for restoration, resiliency and sustainability.”
The MRGO Must Go Coalition was founded in 2006 in response to Hurricanes Katrina and Rita. The Coalition’s mission is to ensure that the wetlands affected by the MRGO are carefully restored in a timely manner. As of August 2015, the MRGO Must Go Coalition included 17 local and national environmental, social justice and community organizations.
Since its inception, the Coalition has served as a liaison between the communities in Orleans and St. Bernard parishes and the US Army Corps of Engineers and other government agencies. The vast organizational resources and expertise provided by the member organizations allow the Coalition to make informed policy and scientific recommendations on the restoration of the ecosystem impacted by the MRGO. More information can be found at www.MRGOmustGO.org.
By Shannon Hood, Environmental Defense Fund
Today is National Oyster Day, and we’re celebrating the holiday with a post about these useful and tasty bivalves and the University of Maryland Center for Environmental Science’s (UMCES) Horn Point Laboratory, which is growing them by the billions.
Previous posts have discussed the ecological and economic importance of oysters, so we won’t spend time on this today. In preparation for a series of other posts on the (r)evolutionary oyster industry, this post will explain their life history and introduce some of the research being conducted to ensure their continued success.
Oysters grow in large colonies that make up reefs. Mature oysters begin to spawn when the water temperature reaches 74-86 degrees Fahrenheit. When the first male or female spawns, others sense it as they filter the water, thus triggering more to spawn.
The sperm and eggs join in the water column. The newly formed larvae will swim and feed for approximately two weeks until they reach what’s known as the pediveliger stage and are ready to attach to a substrate, a process known as “setting.” When an oyster sets, it secretes a glue-like substance and will not move from this location for the duration of its life. At this point, the oyster is known as a spat.
In the lab, this process is much the same as in the wild, however, it takes place in a controlled environment. In this environment, staff are able to control variables such as temperature, salinity and food availability – variables which have tremendous effects on oyster spawning and survival rates.
Aside from their work in growing oysters, the UMCES Horn Point Hatchery is a hotspot for research on all things oyster, including numerous graduate student researchers looking into how salinity affects setting and growth throughout oysters’ lives. Having a good understanding of optimal salinities and answering these questions, we remove yet another unknown in this industry, allowing greater understanding for how to ensure oysters are able to thrive now and into the future.
Oyster populations and harvests are on the rise in the Chesapeake Bay for the first time in decades. In 2004, just 26,000 bushels were harvested from Maryland’s waters. In 2014, Chesapeake Bay harvesters reported their best year in three decades, bringing in 900,000 bushels from traditional on-bottom leases.
What’s the cause of this rebounding industry? It’s no miracle cure, but rather a host of federal and state management practices, a booming aquaculture industry, successful hatcheries that provide a reliable source of larvae and new science that is allowing these bivalves to thrive once again.
What does this mean for Louisiana? Our coastal waters boast some of the best conditions for oyster growth in the nation. Using funds from the Natural Resources Damages Assessment (NRDA) Early Restoration Program, LSU Sea Grant is operating a new, state of the art hatchery on Grand Isle, a hatchery capable of producing up to one billion oyster larvae per year. This increased capacity can add significantly to the production potential of the state’s public and private oyster grounds. Additionally, off-bottom aquaculture and remote setting are looking more and more like realistic options to increase the industry’s success. Stay tuned for future posts about each of these new tools in the oyster industry’s toolbox.
By Steve Cochran, Director, Mississippi River Delta Restoration Program, Environmental Defense Fund
Ten years ago, just after Hurricane Katrina, I was asked to talk to Environmental Defense Fund’s board about the place where I grew up, the New Orleans area that had been hit so hard.
I remember two things about that discussion. One was my voice breaking unexpectedly (and embarrassingly) as we talked through pictures of the Katrina aftermath and came across places I intimately knew.
As an adult, I had developed a love/hate relationship with my home – loving the beauty, the people, the community and the culture, but frustrated by what I saw as the general tolerance of mediocrity and corrupt politics that limited its possibilities. That frustration had pushed the love down, and I had moved away. But there it was again. Sometimes you don’t know how much you care.
The second thing I remember was saying that the Katrina response was a deep test of our governments – local, state and national. As we know now, in that moment, it was a test they failed. But fast forward to July 2, 2015, the day a global settlement was announced in the Deepwater Horizon oil spill case. It was a day when governments rose to the occasion. The result was literally the largest environmental settlement in U.S. history.
The BP Settlement and Louisiana Coastal Restoration
Under the agreement, Louisiana will receive more than a third of the money – $6.8 billion of the $18.7 billion, and $5.8 billion of that is specifically targeted to restoration. The overall restoration total for Louisiana will likely be just under $8 billion, including early restoration dollars and criminal settlements.
These are significant resources at a critical time. Land loss across the coast of Louisiana, exacerbated by the spill, continues at a fearful rate. But we are making progress against that loss, and with the solid state commitment that now exists, and effective plans in place, these resources will allow us to battle back in earnest, with a clear-eyed view toward success.
In particular, the state plans to re-engage the enormous power of the Mississippi River and its sediment through a series of sediment diversions – using the natural land-building capacity of the river by reconnecting it to the delta it originally built. This science-based, innovative approach is the critical piece in our ability to provide solutions at a scale that can match the challenges in the Mississippi River Delta – now the largest restoration effort under way in the world.
Rebuilding Our Coast to Protect Our Communities
About a month after the spill, I was allowed to sit in on a tribal council of the indigenous United Houma Nation. As the oil continued to pour into the Gulf of Mexico, which it would do for another two months, I listened and watched as a man described, through a quiet voice and uncontrolled tears, how he had always looked to the waters of the Gulf and drawn confidence, knowing he could always provide for his family by accepting its gifts. But now all he could feel was fundamental fear.
Money can’t replace that kind of loss any more than it can bring back the 11 loved ones who lost their lives in the accident.
But we must do what we can – and in that context, the BP settlement is a tremendous step forward, because we can restore the Mississippi River Delta, so it can protect this area in the future.
Details matter, of course, and details remain to be decided as the Agreement in Principle is turned into a consent decree. We need to remain involved and vigilant. But it does seem clear that this agreement combines avoiding years of litigation with levels of funding that can truly make a difference.
With these resources, we can go to work to make sure that the largest environmental settlement in our nation’s history also becomes the most meaningful settlement in a place that, well, I love.
By Ezra Boyd, PhD, Disastermap.net, LLC
The Hurricane Surge Risk Reduction System
As we approach the 10th anniversary of Hurricane Katrina and the associated levee failures, the people of the Greater New Orleans (GNO) region face constant reminders that our safety and viability depend on a complex system made of numerous elements that together mitigate risks from hurricane induced tidal floods. The near constant construction of levees, pumps and floodgates over the last decade provides the most visible evidence of this system. Together, these components are termed the structural lines of defense. In addition, work on other important, but less visible, components have also reduced our flood risk. Broadly speaking, the other two major components are the coastal lines of defense and the community lines of defense. Together, these three components comprise the Multiple Lines of Defense Strategy for Sustaining Coastal Louisiana (MLODS).
Beyond a list of 12 separate lines of defense (see figure below), MLODS represents a system that allows us to use the professional tools and standards of systems engineering to assess the current status of storm surge risk reduction. Within the field of systems engineering, a system is defined as: “an integrated set of elements, segments and/or subsystems that accomplish a defined objective.” The 12 lines of defense make up the elements of the system, and systems engineering helps us figure out if they function in an integrated fashion to accomplish the objective of managing storm surge risk.
A recent report from the Lake Pontchartrain Basin Foundation, called “A Systems Engineering Based Assessment of The Greater New Orleans Hurricane Surge Defense System Using the Multiple Lines-of-Defense Framework,” provides a detailed assessment of the current system of levees, pumps, gates, coastal landscape features and community resilience steps that the region depends upon to manage storm surge flooding risk.
System Interactions and Factors of Concern
Once the Hurricane Surge Defense System (HSDS) has been specified as a system, the tools of systems engineering then allow us to identify system interactions that create major factors of concern. A system interaction refers to when the performance of one system element is impacted by the other elements, while a factor of concern is an element or interaction between elements that could potentially reduce the system performance. The report identified and described a number of system interactions and factors of concern. Two of the major concerns are with the Foot of the Twin Spans bridge and the IHNC/GIWW navigation canal (shown here). Both result from interactions between systems elements that affect evacuation effectiveness.
I-10 East Evacuation Route & Chandeleur Islands
Interstate 10 is a major evacuation route. During peak evacuation, an estimated 2,000 vehicles per hour utilize its eastbound lanes to escape GNO. These eastbound lanes cross Lake Pontchartrain on the edge of New Orleans. Since Hurricane Katrina, the bridge, locally known as the “Twin Spans”, has been rebuilt in an $800 million project that raised the bridge to 30 feet above sea level. Not far from the bridge is the rebuilt levee system that provides perimeter protection for GNO. Between the levee and foot of the bridge is an approximately 1 mile section of interstate that is at ground level and outside the levee system. Most of this section of highway is 7 – 8 feet above sea level. However, just before the foot of the bridge, atop of narrow peninsula that has experienced landloss on all three sides, the highway dips to around 6.7 feet above sea level. This low, unprotected section of a major evacuation route is prone to flooding early during storm surge events, thus blocking any further evacuation.
The Chandeleur Islands, a rapidly eroding barrier island chain, are located some 60 miles from the foot of the Twin Spans bridge. Yet, how they perform as a coastal line of defense affects the performance of the I-10 East evacuation route. Hydrological studies have determined that the elevation and integrity of the Chandeleurs influences the timing and height of the peak surge, with the surge peaking 1.5 feet higher and 1 hour sooner if the islands continue to erode. Exemplifying the concept of system interactions, the Chandeleur’s ability to mitigate storm surge impacts the available window of time to evacuate people using the eastbound I-10.
IHNC/GIWW Closure Operations, Vessel Evacuation, and Vehicular Evacuation
The Inner Harbor Navigation Canal (IHNC) and Gulf Intracoastal Watery (GIWW) are two manmade navigation canals within the eastern half of GNO. During Hurricane Katrina, they were major conveyance pathways for storm surge and also the location of numerous levee breeches. Since Hurricane Katrina, the area has been subject to major levee upgrades along with newly constructed floodwalls and floodgates. While these structural improvements provide a potentially much improved level of protection, the gates in particular create a new set of concerns related to system behavior. They also provide another example of asystem interaction that also affects evacuation effectiveness.
Simply put, closing the gates in anticipation of a tropical system is a complicated procedure that must be coordinated with navigational interests, railroads, and the Port of New Orleans. Most navigational vessels are required to evacuate the IHNC/GIWW before a hurricane. This in-turn requires that the vessels pass under a number of drawbridges. Since the drawbridges must be opened to let vessels pass, they then hinder vehicular evacuation of the general population. Here the operations of these structural components (the flood gates along these two canals) impact the performance of the evacuation component, another example of a system interaction that creates a major factor of concern.
These are just two of many factors of concern with the current HSDS. Our report documents others, some small and others major. Maintenance, long term funding, coordination, and public risk communication were the major themes uncovered in our study. Because it is important for the public and policymakers to understand the true level of protection, LPBF continues to build on the momentum create by this report. As step toward addressing some of the issues identified in the report, we have recently launched the Pontchartrain-Maurepas Surge Consortium to facilitate regional collaboration between levees boards, floodplains managers, coastal scientists, and others engaged in storm surge management and risk reduction.
The report, along with LPBF’s continuing efforts at implementing MLODS for coastal flood protection, has been funded by the Kresge Foundation.
Additional resources:No Comments
By John Lopez, Ph.D., Coastal Sustainability Program Director, Lake Pontchartrain Basin Foundation
The Lake Pontchartain Basin Foundation (LPBF) is releasing a report describing the methodology of its Hydrocoast Maps program, a research effort that began in 2012 and monitors water flow, salinity and other factors to better understand the Mississippi River estuary in the Pontchartrain Basin.
What are the Hydrocoast Maps?
The Hydrocoast Maps monitor the distribution of salinity, changes in water quality, and other pertinent information across the Pontchartrain Basin to provide an ongoing, relevant and accurate assessment of basin conditions. LPBF produces a biweekly map series that displays information on salinity, freshwater discharge, water quality, impairments, fisheries activity and a variety of estuarine-related information.
The Hydrocoast Maps provide a snapshot of the condition of the estuary, such as the distribution of saline to fresh water and other relevant factors. LPBF’s goal is for the maps to be useful to a diverse audience – including the general public, but more specifically commercial and recreational fishers, state and federal agency personnel making restoration decisions, scientists and academics.
The biweekly Hydrocoast Map products, and what they analyze, include:
- Salinity Map – isohalines (lines on maps connecting points of equal salinity) and freshwater inflows
- Biological Map – fisheries fleets and closures
- Habitat Map – wetland classification and soil salinity
- Water Quality Map – water quality impairments and fecal coliform counts
- Weather Map – cumulative rainfall, wind and tide data
Current and archived Hydrocoast Maps can be found here.
The Mississippi River Estuary
On the Louisiana coast, fresh water from rainfall and rivers flows seaward and mixes with salt water from the Gulf of Mexico, resulting in a coastal zone called an estuary. This estuarine system also coincides with the extensive deltaic (wetland) plain of the Mississippi River and gives rise to Louisiana’s valuable and productive “working coast.” There are many factors that affect this estuary, such as pollution, fisheries, hydrologic alterations, wetland loss and freshwater inflows. These influences are dynamic and the estuary is shifting daily, but it is also undergoing long-term changes. For example, since 1932 these wetlands have been converting to open water at an unnatural and alarming rate, giving rise to Louisiana’s coastal wetland crisis.
Understanding all of these natural and manmade influences on the estuary is important for local recreational and commercial fisheries, as well as for restoration scientists who may gain a deeper understanding of how the estuary functions and its trajectory of change. Change is inevitable, but we should use the best available data to work with the deltaic system and bring about comprehensive restoration of the Mississippi River DeltaNo Comments