Gulf sand berms: a massive and risky experiment

Wave refraction and sediment dynamics in the Chandeleur Islands (Google Earth)

[For further key information and commentary, see the link provided byCoastal Geologist, Dallon Weathers, in the comments at the end of this post, and note that this topic continues here with further documentation in the latest post]

Politics trumps science and common sense again - my view, clearly, but I am not alone. I wrote earlier this week of what seemed to me to be a lunatic and massive experiment in sediment engineering along 80 miles of the Gulf Coast under the guise of oil protection. Now we read, from the US Army Corps of Engineers:

NEW ORLEANS – Today, May 27, 2010, the U.S. Army Corps of Engineers, New Orleans District Commander Col. Al Lee offered an emergency permit to the state of Louisiana for portions of their barrier island plan.

OK, it's now only 45 miles long - an initial experiment - but it's a huge project nevertheless, of unknown effectiveness and consequences. This post will be largely an attempt to guide readers to the key documents and highlight the key issues - and concerns. Since I concentrated previously on the Chandeleur Islands (otherwise known as the Breton National Wildlife Refuge) and a long stretch of these islands will be the location for one half of this experiment, I'll continue to use them as an example. I'll then provide extracts from the submitted permit and the commentary on it, together with some extracts from a deeply relevant piece of excellent science published last year - that seems to have been entirely ignored. This will be a long post, largely because I want to make available some of those extracts that are important, and so I'll copy them here, together with the links for further investigation. 

And please don't get me wrong - the oil spill is appalling and catastrophic, and every effort needs to be made to minimise the impacts, but "every effort" should be rigorously thought out, all the relevant expertise brought to bear, and the risks of precipitating a wider and longer-lasting crisis as a consequence of the effort thoroughly evaluated. It is not at all clear to me - and a number of higher authorities - that this has been done.

First of all, briefly, the nature of barrier islands, of which the Chandeleur chain, while it lasts, is a classic example. As I mentioned in the previous post, barrier islands are perhaps the most dynamic and ephemeral landforms on the planet, and imagery of the Chandeleurs vividly illustrates this. Even under natural conditions, the architecture and position of barrier islands are constantly changing - maps and charts are out of date by the time they are printed. The fundamental architecture and features of barrier islands is illustrated here (from the University of Texas glossary). The complexity results from the interactions of tides, both coming and going, waves, currents, storms, sand supply and so on. And, as in the case of the Chandeleurs, this complexity is only enhanced by human interference - the need for constant dredging of shipping channels in the Mississippi Delta has essentially starved the islands of sand. 

 

So, as I've described briefly in the previous post, the Chandeleur Islands have had a torrid history and today are but a shadow of their former selves. Nevertheless, there's still a lot worth understanding - and a great deal of effort has been put into doing so, culminating, for the moment, in the publication last year of the results of a long, interdisciplinary, and rigorous study by the USGS and the University of New Orleans. Titled "Sand Resources, Regional Geology, and Coastal Processes of the Chandeleur Islands Coastal System: an Evaluation of the Breton National Wildlife Refuge," this is an extraordinary and fascinating piece of work, available online. Here's the abstract:

Breton National Wildlife Refuge, the Chandeleur Islands chain in Louisiana, provides habitat and nesting areas for wildlife and is an initial barrier protecting New Orleans from storms. The U.S. Geological Survey (USGS) in partnership with the University of New Orleans Pontchartrain Institute for Environmental Sciences undertook an intensive study that included (1) an analysis of island change based on historical maps and remotely sensed shoreline and topographic data; (2) a series of lidar surveys at 3- to 4-month intervals after Hurricane Katrina to determine barrier island recovery potential; (3) a discussion of sea level rise and effects on the islands; (4) an analysis of sea floor evolution and sediment dynamics in the refuge over the past 150 years; (5) an assessment of the local sediment transport and sediment resource availability based on the bathymetric and subbottom data; (6) a carefully selected core collection effort to groundtruth the geophysical data and more fully characterize the sediments composing the islands and surrounds; (7) an additional survey of the St. Bernard Shoals to assess their potential as a sand resource; and (8) a modeling study to numerically simulate the potential response of the islands to the low-intensity, intermediate, and extreme events likely to affect the refuge over the next 50 years.

Results indicate that the islands have become fragmented and greatly diminished in subaerial extent over time: the southern islands retreating landward as they reorganize into subaerial features, the northern islands remaining in place. Breton Island, because maintenance of the Mississippi River- Gulf Outlet (MRGO) outer bar channel requires dredging, is deprived of sand sufficient to sustain itself. Regional sediment transport trends indicate that large storms are extremely effective in transporting sand and controlling the shoreline development and barrier island geometry. Sand is transported north and south from a divergent zone near Monkey Bayou at the southern end of the Chandeleur Islands. Numerical simulation of waves and sediment transport supports the geophysical results and indicates that vast areas of the lower shoreface are affected and are undergoing erosion during storm events, that there is little or no fair weather mechanism to rework material into the littoral system, and that as a result, there is a net loss of sediment from the system. Lidar surveys revealed that the island chain immediately after Hurricane Katrina lost about 84 percent of its area and about 92 percent of its prestorm volume. Marsh platforms that supported the islands’ sand prior to the storm were reduced in width by more than one-half. Repeated lidar surveys document that in places the shoreline has retreated about 100 m under the relatively low-energy waves since Hurricanes Katrina and Rita; however, this retreat is nonuniform. Recent high-resolution geophysical surveys of the sea floor and subsurface within 5–6 km of the Chandeleur Islands during 2006 and 2007 show that, in addition to the sand that is rebuilding portions of the island chain, a large volume of sand is contained in Hewes Point, in an extensive subtidal spit platform that has formed at the northern end of the Chandeleur Islands. Hewes Point appears to be the depositional terminus of the alongshore transport system. In the southern Chandeleurs, sand is being deposited in a broad tabular deposit near Breton Island called the southern offshore sand sheet. These two depocenters account for approximately 70 percent of the estimated sediment volume located in potential borrow sites. An additional large potential source of sand for restoration lies in the St. Bernard Shoals, which are estimated to contain approximately 200 × 106 m3 of sand.

Successful restoration planning for the Breton National Wildlife Refuge should mimic the natural processes of early stages of barrier island evolution including lateral transport to the flanks of the island chain from a centralized sand source that will ultimately enhance the ability of the islands to naturally build backbarrier marsh, dunes, and a continuous sandy shoreline. Barrier island sediment nourishment should be executed with the understanding that gulf shoreline erosion is inevitable but that island area can be maintained and enhanced during retreat (thus significantly prolonging the life of the island chain) with strategic sand placement.

Here's but one of the many illustrations from this report, an example that demonstrates that the vulnerability of barrier islands is not simply in the face of major storms, but as a result of normal, natural, wear and tear of wave and weather. LIDAR (Light Detection and Ranging) technology is a highly-accurate means of mapping a surface, and the illustration shows the surface of a segment of the Chandeleur chain at intervals after Hurricane Katrina. If the changes occured only after a hurricane, followed by a period of stability, then the sequence of surveys (in different colours) would all overlap. But they don't - over the nearly two years of normal conditions after Katrina, dramatic shifts in the island landscapes are clear. We intend to build a sand berm here?

 

The report provides a wealth of data that inform our understanding of sediment movement and sediment budgets along the the islands, including the key fact that longshore transport diverges in opposite directions from a central point - sand is carried northward along the northern half of the chain, southward along the southern. But the fact remains, as the report makes clear, that there are discrepancies and the details of the sand budgets remain elusive.

But the report anticipates its use as a guide to thoughtful restoration of the islands, and sets out some preliminary guidelines:

Implications for Management Planning

If the decision is made to restore any portions of the Breton National Wildlife Refuge, the restoration techniques should mimic the natural processes of early stages of barrier island evolution. These natural processes include lateral transport to the flanks of the island chain from a centralized sand source that will ultimately enhance the ability of the islands to naturally build back barrier marsh, dunes, and a continuous sandy shoreline. Barrier island sediment nourishment should be executed with the understanding that gulf shoreline erosion is inevitable but that island area can be maintained and enhanced during retreat (thus significantly prolonging the life of the island chain) with strategic sand placement if the following criteria are met:

1. Nourishment sand recovered from deepwater sinks at the flanks of the island arc is reintroduced to the barrier sand budget at a centralized location that is chosen on the basis of longshore sediment transport predictions;

2. Distribution of naturally occurring hurricane-cut passes is maintained as storm surge/overwash pathways;

3. Sand is placed at a centralized location along the island arc where it will naturally disperse to the flanks;

4. Sand reserves are strategically placed in the backbarrier as shore-perpendicular platforms over which the island can migrate; and

5. A naturally well-established (decadal to century-scale) backbarrier vegetation is maintained for long-term sustainability.

As will become clear, the now approved sand berm project is in complete conflict with these recommendations. Yet the project was originally (and, I would say, cynically) submitted as a "Restoration Project."

The permit now issued by the Corps of Engineers ("Building Strong"), together with some history and documentation of comments is available in its entirety online (although its entirety still leaves much to be desired). The only location maps provided are reproduced below, first the regional setting with the two stretches of berms marked, one west of the delta and one in the Chandeleur chain. The details, such as they are, of the Chandeleur segments are shown in the second illustration (I've highlighted the approved stretches in red). I shall restrain from further comment.

   

The currently approved "borrow area" from which sand is to be dredged is at the end of the delta (Pass a Loutre); while the USGS/University of New Orleans study identified potential sand sources in banks off the Chandeleur Islands where the character of the sand is compatible with the requirements of island restoration and natural processes, there is no sign in the permit that this has been considered for the approved borrow area - it is, after, all, at the mouth of the delta, not in a barrier island setting. The USGS report had the following to say about dredging considerations, which should perhaps be taken note of by the bermers:

Hydrodynamic Impacts

The removal and relocation of sediment by dredging alter the sea floor topography and consequently the bathymetric profile of the dredged area. A consequence of sediment dredging is an increase in the water depth at the dredged area. The direction and magnitude of currents and sediment transport cells are in part controlled by sea floor topography; thus, currents, sediment transport cells, and wave climate offshore of the Chandeleur Islands could be altered by dredging of the recommended borrow sites. Quantitatively assessing these potential alterations is paramount because perturbations of these conditions could adversely impact the surrounding coastline and islands; however, the potential effects of dredging in the area have not yet been quantitatively studied, and it is unreasonable at this time to attempt to predict the exact effect that dredging of recommended sites would have on the eastern Louisiana continental shelf. It is common practice to use numerical models to assess the impact of dredging on currents, sediment budgets, and wave climates.

And here's the only berm construction plan contained in the permit:

 

But rather than my observations, let's look at the comments of the agencies that were consulted, first of all, a telling extract from the Department of the Interior (there is much more):

Given the size of this project and the fact that the project cannot be completed within a timeframe needed for it to provide protection to the Delta, we do not think the risks inherent in proceeding without more environmental study and knowledge are acceptable. We are however open to reviewing any projects proposed by the State that could be executed in time to prove helpful in minimizing the devastating impacts of this spill.

And then from the Environmental Protection Agency:

SUMMARY OF EPA CONCERNS

In these comments, EPA is only addressing the 40 miles of berms described above (E3, E4, W8, W9, WIO, WI 1). EPA continues to have significant additional concerns about the original proposals to build 80-120 miles of berms. Clearly a project of the 80-120 mile scope is so significant that under normal permitting procedures it would likely require full NEPA review-and NEPA review of this project under normal permitting procedures would likely be required as well.

As described more fully below, although the proposed permit transmitted by the Corps in their email dated May 24 for the permitting ofE3, E4, W8, W9, WIO and W11 has additional information to support the reduced size project proposal reviewed by EPA on May 23, EPA remains concerned about: (1) the effectiveness of this project at actually stopping the oil from moving into estuarine waters and marshes; (2) whether the proposed project realistically can be constructed in time to have a measurable effect on controlling movement of oil into interior estuarine waters and wetlands (and whether the berms could sustain the impacts of hurricanes or other Gulf storms or be washed away); (3) whether the constructed berms themselves, dredging activity, barge and other boat equipment traffic, and floating pipe for sediment transport could exacerbate the emergency situation in the Gulf; (4) the impacts of construction of these berms and longer term impacts on aquatic species and wildlife and on sensitive environmental resources such as those that exist in the Chandeleur Islands (in particular the west side of the islands that have extensive seagrass beds), (5) the potential estuarine sediment transport, salinity, and hydrologic impacts over the longer term; and, finally, (6) the lack of sufficient testing of borrow areas for potentially contaminated sediments prior to dredging and the potential longer term impacts of contaminated sediments being used for the berm as well as the ultimate disposition of berm materials that would become contaminated with oil if the berms are effective in stopping the oil from moving.

All these issues are addressed in greater detail by the EPA, but here's one particular point - the management of oil-soaked sand:

Planning to address contaminated berm sediments: EPA continues to have concerns that the draft permit gives no consideration to either short or longer-term planning, responsibility or costs for removal/remediation of berm sediments that become contaminated from intercepting waterborne oil. The Corps' draft permit states, "This permit does not address the applicability of the proposed project to the spill response effort, which is a decision to be made by the NIC in consultation with Federal OSC." Designing and constructing a structure to arrest contaminants without discussing and deciding how contaminated materials will be properly managed and removed from the environment is of great concern in this highly dynamic and vulnerable coastal environment. Safe and rapid removal of contaminated sediments would be critical for ensuring a hurricane or tropical storm does not subsequently disperse these materials into bays and wetlands. It is also critical to ensure that potential upland disposal of sediments that have been contaminated with oil does not create Environmental Justice or other environmental problems by potentially harming the coastal communities we seek to protect.

And the comments from an NGO, the Gulf Restoration Network, sum up very succinctly the major causes for deep concern about this project:

I am writing on behalf of the Gulf Restoration Network (GRN), a diverse coalition of individual citizens and local, regional, and national organizations committed to uniting and empowering people to protect and restore the resources of the Gulf of Mexico. We, like many of our colleagues who have been following the BP oil drilling disaster response closely, have recently heard about a proposal submitted to the U.S. Corps of Engineers (Corps) to "request emergency authorization to perform restoration work on the Chandeleur Island and also on all the barrier islands from East Grand Terre Island eastward to Sandy Point for purposes of enhancing the capability of the islands to reduce the inland movement of oil from the sediment via cutterhead pipeline dredge from adjacent water bottoms Gulf ward of those islands, and depositing the dredged material in protective berms along those islands." While we share the State's desire to protect our coast from the harmful effects of the ever-growing threat of of! fouling our wetlands, based on conversations with scientists, conservationists, as well as federal resource agencies, we do have some concerns and suggestions regarding this proposal:

I. Concerns

1. The timeline of this proposal

Given the small amount of information in the drawings associated with Louisiana's request, as well as the complexity and diversity of existing barrier islands, it seems ill advised to move forward with such a massive project on such a short time frame. Additionally, it seems that it would take quite a long time to build the sand barriers. Since oil is already being seen within the barrier islands, would these barriers effectively keep the oil out?

2. Limited amounts of sand and sediment

When it comes to coastal restoration, it has become exceedingly clear that one of the limiting factors is the amount of sediment available for restoration purposes. This must be taken into account when considering this sand barrier plan. Sand used for this project will not be available for other restoration projects, especially if it is fouled with oil. We are not saying a balance cannot be struck here, but limited sediment resources must be taken into consideration.

3. Impacts of oil on new barriers

We would like to see more information as to the efficacy of building and enhancing barrier islands if the intention is that they might become polluted with oil. How will these barriers be cleaned? Will the sand need to be removed and disposed of, thus reducing the amount of sediment we have for restoration?

4. Impacts to hydrology

Given the information in the drawings submitted to the Corps for their review, there does not appear to be any analysis of the effects the sand barriers might have on the hydrology inside the barrier islands. Some questions that need to be answered are: Will these barriers restrict the hydrology so water within the barriers will rise? Will the constricted passes between the barrier islands increase velocities such that flow will increase, potentially pulling oil towards the coast during certain tidal periods?

5. Impacts to fish and marine life

The State's proposal does not include any analysis as how the proposed barriers would impact fish, other marine life, water fowl, and other wildlife. An obvious goal of these barriers should be to protect wildlife. Given this, we feel that there must be a thorough analysis on what impacts these barriers might have on wildlife in our oceans, estuaries, and existing barrier islands.

6. Coverage under general permit

We understand that the BP oil drilling disaster is a disaster of unprecedented proportions. However, we are concerned that Louisiana is proposing to have such a large project covered under a general permit (NOD 20). General permits are intended to have negligible impacts individually and cumulatively, however this project will certainly have impacts that would normally require a full Environmental Impact Statement (EIS) under the National Environmental Policy Act (NEPA). While we acknowledge that this disaster requires regulatory flexibility, general permits were never intended to address massive projects with potentially significant environmental impacts. We find the precedent set by this action disturbing.

"We find the precedent set by this action disturbing." As, I would think, do many people. The Corps of Engineers permit may list 33 conditions, but this is a giant step into the unknown - the risks versus the benefits have not been addressed.

And one of the conditions is, sensibly, not to build berms across the major tidal channels that segment the barrier islands. Fine, but then how is the oil stopped? And where, in the image at the head of this post, are the major channels, versus the countless number of sedimentologically dynamic breaks in the chain? Look closely at the image, at the complexity of this active wave and sediment system.... a good place to build a berm?

Comments

[BrianR]

Michael, this is an important post ... I've already linked to it on Twitter and it's making the rounds. Thanks for writing it!

[Dallon Weathers]

I have a similar opinion:
I think that a response to the oil needs to be swift, effective, adaptable, and sustainable. Also, it needs to follow the over arching rule to respond in a way that does not add to the harm that oil would do alone. I truly do not think it meets any of these requirements.

For interested readers it is found here:
http://nola.humidbeings.com/posts/detail/132032/Berm-Barrier-Open-Letter-to-Adm.-Thad-Allen

[Sandglass]

Dallon - many thanks for this - it's really helpful to have the detailed information from a professional who is intimately familiar with this environment and this issue.

Note:Dallon is a coastal geologist based at the Pontchartrain Institute for Environmental Resources,
Department of Earth and Environmental Sciences Coastal Research Lab at the University of New Orleans. It was this group who conducted, with the USGS, the comprehensive study that I have referred to and used extensively in this post. Readers should follow Dallon's link - there's a lot of valuable observations and commentary there.