Through The Sandglass

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?

80 miles of sand berms???? Experts express doubts.......

 

[Note that there is now a follow-up post to this, documenting the approval of this plan, together with commentary from US Government Agencies and a summary of a detailed report on the sediments of the Chandeleur Islands]

Louisiana. The President of Plaquemines Parish has presented a plan for dredging and construction of eighty miles of six-foot sand berms along the coast on either side of the Mississippi Delta as protection against the oil spill (the original plan had been for twenty-foot berms). The illustration above is from the plan as published online. This was described in a New York Times article a couple of days ago, and I have taken the liberty of reproducing the bulk of the article here (I left out BP’s comments since I felt that they were hardly objective):

Experts Express Doubts on Sand-Berm Proposal

By JAMES C. McKINLEY Jr. and JOHN COLLINS RUDOLF

Published: May 21, 2010

VENICE, La. — State officials here are imploring the federal government and BP to build 80 miles of sand berms and plug holes in barrier islands in a desperate effort to stop oil from the Deepwater Horizon spill from destroying marshes, sounds and bayous.

But many experts say it is not at all clear whether dredging companies could build up the barrier islands quickly enough to save the marshes. They are also concerned that the kind of sand berms envisioned in the plan might wash away quickly after a couple of storms, wasting scarce sand in the region.

Still, Gov. Bobby Jindal and local officials say the berms represent the state’s best hope of protecting the fragile Mississippi Delta and its fisheries. The officials are frustrated with what they see as bureaucratic inaction. “They haven’t given us any reason for the delay,” Mr. Jindal said Wednesday.

So far, the Army Corps of Engineers has not granted the state’s request for an emergency permit for the plan. The Coast Guard, which can force BP to pay for a $350 million dredging project, has yet to make a decision about it.

For several years, the state has been trying to get financing for a similar project to rebuild the Chandeleur Islands, a chain of low-lying barrier islands in the delta that lost more than 80 percent of their surface area during Hurricane Katrina in 2005. But officials say they are not simply taking advantage of the oil spill to finance a long-hoped-for project.

Billy Nungesser, the president of Plaquemines Parish, who has been pushing for the sand-berm project, said he hoped BP would pay the cost of building what amounts to a six-foot seawall over the next six months. The state’s earlier plan had called for the islands to be rebuilt to about 20 feet above sea level.

At stake, Mr. Nungesser said, are Louisiana’s seafood and sport-fishing industries. “If we don’t do something, shame on us,” he said.

On May 11, the state Coastal Protection and Restoration Authority of Louisiana requested the permit from the Army Corps of Engineers to create the barrier in the Gulf of Mexico out of sand dredged from a site several miles offshore. The barrier would stretch along the coastline on both sides of the Mississippi Delta, from Chandeleur Sound in the east to Barataria Bay in the west.

Gregory W. Stone, director of the Coastal Studies Institute at Louisiana State University, said that dredging and pumping large amounts of sand amid Louisiana’s complex inlets and bays could harm ocean life. Dr. Stone said any plan required closer study before it is put in place.

“I understand that time is of the essence, but I really think that we’re taking a gamble here,” he said.

The general idea of protecting the area’s vulnerable wetlands by buffering coastal islands with dredged sand is not particularly controversial. Similar plans have been in the works for years, and small-scale projects have had success in the recent past.

“The concepts behind this are probably sound,” said Denise J. Reed, a wetlands expert and interim director of the Pontchartrain Institute for Environmental Sciences at the University of New Orleans. “One of the reasons we’re so worried about the oil coming into the marshes is the barrier islands are so degraded. We don’t have a very intact shoreline.”

The governor’s plan would not permanently rebuild degraded coastal islands — a delicate and complex process that has been planned for years. A temporary sand barrier could wash away in a matter of months, experts said. And the type of sand necessary for long-term coastal restoration is in short supply along Louisiana’s shoreline.

“If we use the good sand that we have for this quick-and-dirty berm, and a storm comes in and spreads it around, we’ve lost the major sand resource that we wanted to use for barrier-island restoration,” Dr. Reed said. “We could compromise the long-term restoration of the coast for a short-term gain.”

Right now, the chain of barrier islands has very little protection. Asbury H. Sallenger Jr., an oceanographer with the United States Geological Survey, said the Chandeleur Islands lost the majority of their surface area during Hurricane Katrina. Even a strong wind can push a surge of water over the island, he said.

But Dr. Sallenger, like other experts, noted that the dredging project would take months to complete, and the oil is already showing up in the marshes. “My first question is whether such a thing could be done, from a scientific basis, quickly enough to be useful,” he said.

..........

State officials acknowledge there are concerns about environmental impacts from building the berms. A number of barrier islands that would be built up by the dredging operation are sensitive habitats for turtles and other species, and some are protected bird sanctuaries. Heavy construction could further disturb these populations, which are already under threat from the oil slick. But they are willing to take that risk, given the potential damage the oil slick could cause.

Still, a spokesman for the Army Corps, which will oversee the permit process, said that even under an expedited basis, the dredging project would need to comply with federal environmental regulations.

Mr. Nungesser said the proposal did not need more than a few days’ study. Similar projects have been extensively reviewed by local experts in coastal restoration, he noted.

“It’s not something that we dreamed up overnight,” he said.

I really don’t know where to begin, since there are so many extraordinary aspects to this idea, several of which have been commented on in the article. The total cost is listed as $235 million, but there is no clear mention of how much sand would be required, where it would come from, its compatibility with its new environment, and how long it would take – never mind how long it would last. On the latter point, just for the record, it’s worth pointing out that the plan’s satellite image (at the head of this post) clearly predates the almost complete disappearance of the Chandeleur Islands that curve north from the delta; as I have commented before, barrier islands are amongst the most dynamic and ephemeral natural landforms on the planet, and those, like the Chandeleur Islands, that have been starved of sediment supply by human interference are particularly vulnerable. The wonderful historic imagery facility on Google Earth demonstrates this dramatically. Below (north to the right) are images from progressive dates from 1998 to 2009, the arrow registering the same point in each. During that period, nine hurricanes hit the Louisiana shoreline – Frances, Georges, Lili, Ivan, Katrina, Humberto, Gustav, Ike, and Ida. The most devastating was, of course, Katrina whose destruction of what was left of the islands can be seen in the 2005 images.

 

Today, there is almost nothing left of the islands – but we propose to build a SAND BERM?

[http://www.nytimes.com/2010/05/22/us/22berms.html; see also http://coastal.er.usgs.gov/hurricanes/katrina/photo-comparisons/chandeleur.html for thorough and depressing documentation of the disappearance of the Chandeleur Islands; I have commented before on attempts at large-scale sand “nourishment” projects and interfering with sediment budgets.]

Beach patterns: Accretionary Wedge Geo-Image Bonanza

Predictable, I guess, this contribution. But to me, the endlessly fascinating patterns sculpted on a beach are quintessential illustrations of nature playing with scale, process, and ephemerality. I realise that I've cheated a bit here - three images rather than one, but I'd actually prepared a bunch more before I appreciated that Chris and Anne, hosts of this Accretionary Wedge at Highly Allochthonous were asking for a photograph. Previous similarly themed posts from guest photographer Larry Deemer, and my visit to Cap Ferret on France's Atlantic coast.

Indoor dunes: challenges of complexity and scale

A couple of weeks ago I was delighted to find myself an invited guest on the BBC Radio 4 show, The Museum of Curiosity. It’s pure entertainment – hosted by John Lloyd, the comedy writer and producer of, for example, Not The Nine O'Clock News, Spitting Image and Blackadder, it features three guests who, after an introductory session of general discussion and humour, are invited to submit their nomination for inclusion in the mythical museum. Such donations can be real or imaginary but they must be curious and they should be funny; previous items have included The Big Bang, a Yeti, Silence, Father Christmas, and the Battle of Waterloo. Knowing that the museum is vast, I donated a Sand Dune Choir, a group of dunes, each selected for emitting a representative note from the musical scale (as individual dunes around the world really do); my assumption was that these dunes would migrate around the museum, spontaneously booming, squeaking, and singing, until, one day, they would get their act together and burst into a rendition of the theme from Lawrence of Arabia, or perhaps Gone With the Wind.

I enjoyed, amongst other aspects of the concept, the idea of indoor dunes, simply because it’s so absurd; but it’s also something of a problem for serious scientific research. Dunes and the laboratory environment simply don’t mix – for any number of reasons. Primarily, of course, it’s a problem of scale, in the sense not only of the size of a typical sand dune (never mind a dune field), but also of time: the evolution of a single dune takes place on a scale of years. Small-scale features of windblown sand – ripples etc. – can be reproduced and analysed in the laboratory, and they have been for decades. Ralph Bagnold (“the man who figured out how deserts work”) was doing this kind of fundamental research in his self-designed and -constructed wind tunnels seventy-five years ago, but scaling up to dunes was out of the question. Even the largest-scale experiments have produced moving piles of sand, but nothing resembling a dune.

The science of understanding how dunes work has thus relied on two entirely separate approaches: field observations, measurement, and description of real dunes, and attempts to scale things down in the laboratory. Scaling up and scaling down are, of course, standard operating procedure in many research laboratory disciplines, and the approach can produce powerful insights. But every step taken, however carefully and proportionately calculated, that departs from the natural scale, changes the calibration to reality. The complexity and dynamics of something like a field of sand dunes – for example, the Saharan dunes in the image above - are extraordinary, and the natural processes involved operate on a multiple orders of magnitude range in scale: from nano-scale interactions between individual grains to regional scale feedback between geomorphology and atmospheric boundary layers. Modelling such a system with accuracy is simply out of the question, whether the models are physical or mathematical.  

But that’s not to say that such approaches are not worthwhile – they can shed light on the complexity. A fascinating example of this has just been published in the new issue of the Geological Society of America’s journal, Geology. “ Formation and stability of transverse and longitudinal sand dunes” reports the results of modelling by three researchers at laboratories in Paris (full reference below). Dunes come in all shapes and sizes and varying degrees of complexity. Perhaps the most familiar, and apparently the simplest, is the crescent-shaped barchan dune, commonly occurring in groups of different sizes, a herd moving slowly across the desert floor as sand is blown across their upwind slopes and avalanches down the steep front; the “horns” point in the direction of movement. Ralph Bagnold recognised that barchans tend to form in a setting where one wind direction is dominant year-round, a relatively simple situation – but he also recognised their complexity, smaller dunes travelling faster than larger ones, catching up with and merging with them, only to eventually “reappear” on the downwind side. This gives the strange appearance of parental dunes “breeding” offspring – a process that has been much-studied and remains the subject of scientific debate (and a separate post).

 

There are many areas of the world’s deserts where the wind directions vary, depending on the time of year, often with two distinct directions dominating equally. Under these circumstances, long, linear dunes form, sometimes at right angles to the average wind direction (transverse dunes), sometimes roughly parallel (longitudinal dunes, image below); it is these types that the French researchers set out to understand better, remarking, with some degree of understatement, in the paper’s abstract that “In both cases, their large width (hundreds of meters) and evolution time scale (years) strongly limit the investigation of their dynamics and thus our understanding of such structures.”

 

It has been established for some time that the specifics of the shapes of these dunes, and their evolution, depends on sand supply versus wind direction, and the angle between the two directions. Transverse dunes often appear to be unstable, developing into sinuous shapes and eventually, if the supply of sand is too low breaking up into “barchanoid ridges” or, ultimately, true barchans. But sorting out the details is difficult: the physics of sand dunes (as originally established by Bagnold, whose work is still referenced in this paper) reflects the coupling of sediment transport by a fluid and the modification of the flow by the resulting shape of the bedform. Critically, the whole process, and in particular the minimum size of a dune, depends on the density ratio between the grains and the fluid. For quartz sand grains and air, this ratio is, of course, very large and so the minimum size of a dune is measured in meters – difficult to replicate in a laboratory. But change the fluid to water, and the ratio and hence the scale of everything, reduces by a factor of a thousand; here’s a way of scaling things down and making sand dunes indoors. But surely changing the fluid from air to water changes the whole game? Well, yes and no – sand dunes on all scales occur under water where strong currents operate, including the gigantic dunes on the floor of San Francisco Bay, and they share many of the features and behaviours of desert dunes. But they are also, inevitably, different. However, there have been a number of research projects that have successfully modelled dunes in the lab on a very small scale under water, and the paper in Geology is but the latest example.

The apparatus designed to model dune formation under two different wind directions is clever (diagram below). The plate is 90 cm wide and 1m long, and includes a circular rotatable element on which sand, a couple of millimeters thick is placed. The whole thing is immersed in a water tank and driven quickly forwards, replicating the fluid flow over the sand. The plate is then withdrawn to its original position, but very slowly so as not to disturb the sand, the circular part is rotated by a few degrees and the whole thing moved forward again, this time under a different “wind” direction. Repeating this over long periods of time – typically several days - and with varying angles between the two “winds” allows a wide variety of sand geometries to be produced; the bedforms created in the sand are illuminated by laser and photographed.

 

Here’s one of the illustrations from the paper, the top images being satellite views of transverse dunes “degenerated into barchanoid ridges” (White Sands), oddly mixed patterns showing both longitudinal and transverse forms (Taklamakan, China) longitudinal dunes extending for several tens of kilometers (Saudi Arabia). The lower three images are of experimental results that replicate these patterns on a small scale, the blue arrows and the angle θ showing the two wind directions in each case.

 

The experiments demonstrate that an initially flat sand bed first develops structures that are  perpendicular to each wind direction, a complex pattern of superimposed forms that then evolves into dunes that progressively align perpendicularly to the mean wind direction if θ is less than 90 degrees (transverse) or parallel to the wind if the angle is greater than 90 degrees. But the transverse dunes often quickly disintegrate into barchanoid ridges. The longitudinal (sometimes also referred to as “seif”) dunes are stable and long-lasting, as long as an ample supply of sand continues to be available.

The paper, and its ancillary “data repository,” both available online but unfortunately only to GSA subscribers, contains much additional information and further detail, including numerical modelling work that supports the results of the physical experiments.

This is interesting work, but it does raise a few questions. For a start, the experiment used ceramic beads rather than real sand – not a problem in itself, but, after all the scaling down achieved in the overall model, these beads were between 65 and 120 micrometers – 0.065 to 0.12 mm – in diameter; this is the size range of fine real sand – but everything else is scaled down. Surely this is yet another step away from reality? The dunes produced experimentally range up to 3mm high, in other words, a pile 40 or so grains thick…. And yes, nature tends to enjoy patterns that are independent of scale (fractals and so on) but looking at the results shown in the “ABCD” figure above, the scale contrast is a factor of 400,000. There is much to think about in self-similar natural patterns that seem scaleless – but if we are producing patterns on the miniature scale that simply look like those on the scale of landscapes, are we reading too much into this, are we bewitched by appearances? And there remains the question of water versus air – yes, the basic physics of the transport of granular materials can be described simply in terms of fluid properties, but on the nano-scale could there not be important differences? All in all, I can’t help remembering the words of the great Werner Heisenberg, he of quantum physics and the uncertainty principle:

What we observe is not nature itself but nature exposed to our method of questioning.

So my indoor singing sand dunes in the Museum of Curiosity must remain there. One of the authors of the paper I have described has been a leading researcher on how dunes spontaneously emit sound – for a long time he was doing this in collaboration with a colleague, but their ideas diverged and they fell out. It’s reported that they now ignore each other completely.

[The Geology paper is: Geology 2010;38;491-494, E. Reffet, S. Courrech du Pont, P. Hersen and S. Douady; Formation and stability of transverse and longitudinal sand dunes. For a spectacular gallery of the diversity, complexity, and wondrous beauty of dune patterns, see http://www.wired.com/wiredscience/2009/12/deserts-gallery-1/]

The sands of Tatooine

For visitors to Tunisia who tear themselves away from the hotel-strewn beaches, the hinterland has much to offer. Yes, the seemingly endless olive groves give way to rather stark landscapes, broken only by more olive groves, protected by fences of prickly pear cactus, and villages for which the word “thriving” does not immediately spring to mind, but the towns preserve the country’s diverse cultural history and the oases, the Atlas Mountains and the desert beckon. Not far from the Algerian border and the most southerly slopes of the Atlas, is the oasis town of Tozeur; its water was originally entirely from natural sources, but it is now supplied from deep wells, requiring cooling before use. There are several standard excursions on the tourist trail in this part of the country, including through the surrounding sand dunes, partially stabilised by vegetated fencing, across the salt flats and past herds of grazing camels, into the foothills of the mountains. Dramatic landscapes, spectacular geology – and the largest and most stunning chunks of desert roses that I have ever seen.

 

But a major tourist draw is the history of the making of the Star Wars movies: Tunisia provided many of the locations, particularly for the scenes of Tatooine, the lawless home planet of Anakin and Luke Skywalker, scavenging ground for the Sand People (aka the Tusken Raiders) and the malevolent and miniature Jawa, roaming the desert in their Sandcrawlers, searching for droids to abduct.
Not far to the west of Tozeur, on the fringes of the Sahara, Tatooine lives on (with only one sun): the sets were robustly built and remain today amongst the dunes, an essential destination for the tourist. So off we went, in the inevitable clapped-out Toyota Landcruiser, ineptly driven (where was an X-34 Landspeeder, or even a Sandcrawler, when I needed one?). And then, there it was, a cluster of buildings and moisture vaporators that spirited me back to those hours in the cinema (memorable) and the toy stores (definitely forgettable). But, keeping an eye open for Storm Troopers, I hurried past towards the dunes (see header photo) - a strong wind was blowing and there was sand on the move to be enjoyed, saltation red in tooth and claw. Ignoring (as I would later regret) the inadvisability of photography in conditions of blowing sand, I nevertheless relished watching  – and recording – the swirling flurries of grains sweeping across the surface, the constant avalanching of the steep faces of the dunes.

 

The sands of Tatooine are beautiful, fine, frosted, and rounded to the point where the feel is like silk flowing through your fingers.

 

There are several different locations around Tunisia that were collaged into the scenes of Taooine, among them the remarkable troglodyte dwellings of the area around Matmata – Luke’s family home is a hotel:

 

And between Tozeur and Matamata is the vast and spectacular expanse of the Chott el Djerid, a salt lake, best visited at dawn. 

   

[Star Wars scene from http://www.originalprop.com/blog/ ]

The Geoblogosphere: a commentary

 

Curious about the cultural dimensions of the International Geoblogosphere, and with the impression (without much in the way of supporting statistics) that the UK earth science "community" lags behind international colleagues in the extent to which it has embraced  this medium of communication, I recently wrote a piece for the Geoscientist, the magazine of the Geological Society here in London. Including helpful commentary from Chris Rowan, the intention was to stir things up a little; so far, it has appeared only on the Geoscientist online site, and, while circulating around the discussions of the already-converted, so far has not proved particularly provocative (to my knowledge). Posting it here will, I appreciate, largely reach that same group (the small but much-appreciated readership of Through the Sandglass), but I look forward to comments and suggestions; for example, the Geological Society holds an admirable number of meetings on diverse topics every year - disseminating the highlights via the blogosphere would seem to me to be a great idea.

The Geoblogosphere

Blogs. The self-absorbed ramblings and rants of adolescents of all ages? Political and social tirades from grinders of the well-honed axes of zealotry? Mindless and breathless accounts of minor celebrities and nonentities? Well, yes. But is there also wheat to be found amongst the piles of chaff? The answer to that too is an emphatic “yes”, and I will argue here that the potential value of this much-derided form of communication is under-appreciated and under-exploited, particularly here in the UK.

Until a little over a year ago, I was very much in the derisive camp: I had never looked at a blog and had no intention of doing so. Then the University of California Press, who had kindly and of course wisely agreed to publish my book, pointed out to me that many of their authors set up a blog to help publicise their work, and suggested that I might do the same. I did, with the aspiration that my efforts should represent a few grains of wheat as well as sand. And, in doing so, I discovered, to my surprise and pleasure, just how many valuable blogs there are out there, and how powerful they can be in initiating rewarding lines of communication that otherwise would simply not be open. I discovered the cumbersomely but aptly named geoblogosphere, a global community of geologists who write blogs. There are, literally, hundreds of geoblogs: while the dominant language is English, it is a truly international community, and, while the majority of the writers are academics (faculty and students), included are geologists of all professional stripes as well as freelancers and enthusiastic non-professionals. The theme, content, character, and style of these blogs are, unsurprisingly, diverse – some are more light-hearted than others, some are seriously scholarly, but almost all are informative and entertaining.

So far, so well and good – but what’s the point? Why do these geologists write blogs and what is their value? A recent survey of the geoblogosphere conducted by Lutz Geissler of the Technical University Bergakademie in Freiberg, in collaboration with Robert Huber of the University of Bremen and Callan Bentley of Northern Virginia Community College, helps answer the first question and informs the second. The equally top-ranked responses to the question “why do you blog?” were “to inform”, “to share knowledge”, and “to popularise the geosciences” (followed closely by “to have fun”). Combine this motivation and energy with the significant audience for many of these blogs, and there is arguably the prime value: knowledge-sharing and outreach. From my own experience I take equal pleasure from the virtual conversations that my blog has stimulated with professional geologists and the informed and enthusiastic “interested public”. I not only enjoy, but learn from the selection of geoblogs that I read regularly, taking advantage of the scope of their reports and their links to research news and geological events that, chances are, I would not have otherwise come across. I subscribe (largely online) to several professional journals, but, for sheer breadth of supplementary coverage, the geoblogosphere is unequalled.

But what is this content, what do geoblog writers write about? The majority write about their own work and scientific articles that interest them in the geosciences in general. The geoblogosphere can thus be categorised in a number of different ways – according to discipline (sedimentology blogs, palaeontology blogs, seismicity blogs, and so on), to geographical location and focus, and to specific projects and events (an Ocean Drilling Program leg, for example). Then there are blogs directed at a specific audience – earth science teachers in the U.K., for example, can find valuable support in blogs such as Keele University’s http://earthlearningidea.blogspot.com/. What the majority have in common, however, is that they are current and immediate. Whether reporting on an ongoing research or fieldwork project, a volcanic or seismic event, providing links to newly published papers, or seeking ideas on the design of a new course, these blogs represent a unique means of rapidly disseminating – and accessing – information and ideas.

And it is not just individual scientists who take advantage of this – many institutions and professional societies, particularly in the U.S., maintain blogs or continually updated news sites; the USGS is an excellent example (see http://www.usgs.gov/newsroom/). It is within this context that the currency and immediacy of the blog format provides unique value: reporting on geoscience conferences and meetings. Not only do the Geological Society of America and the American Geophysical Union actively encourage and support individuals blogging from their conferences, but the AGU published its own blog of the recent annual meeting in San Francisco – http://www.agu.org/blog/fm09/. Through the combined efforts of the host institution and individuals writing about sessions they had just attended and papers they had just heard, professional scientific news is disseminated with unparalleled immediacy.

Live conference reporting represents one aspect of the serious science end of the spectrum that is the geoblogosphere, but it is not the only one. Chris Rowan, at the University of Edinburgh, together with Anne Jefferson at the University of North Carolina, publishes the widely respected Highly Allochthonous geoblog (http://scienceblogs.com/highlyallochthonous/). Chris is far closer to the research coalface than I am, and writes:

At its core, blogging is about sharing; in the case of (geo)science blogs, what is being shared is your expertise and your passion for geology. When writing about a recently published paper, you can provide some depth to those interested in not just what we know, but how we know it. By providing a glimpse into how scientific ideas are debated and destruction tested against reality within our community, you help to chip away at the misunderstandings of the scientific process that remain well-entrenched in the public mind, and are all too easily exploited by the unscrupulous, to all our detriments. I personally believe that as a publicly funded scientist, sharing knowledge is as important a part of my duties as generating it in the first place, and blogging is an effective and powerful tool for discharging this duty.
But beyond this, I have a much more selfish reason for investing my time in writing a blog: it makes me a better scientist. I have discovered that my thinking about science – my research, the work of others, basic concepts in our field – becomes much more coherent after I have been forced to properly articulate it. I also find myself properly engaging with a much broader range of geological subdisciplines, counteracting the natural pressure to focus only on my narrow area of research. Furthermore, I'm sure that writing regularly for my blog has greatly improved my communication skills in the conference hall and the lecture theatre - after all, the ability to clearly explain your thoughts to others only comes with time and practice. Finally, it allows you to have a bit of fun; amidst the day-to-day grind of lab work and administration, communicating your excitement about a new geological discovery, or sharing your appreciation of a beautiful geological image, or simply interacting with interested readers in your comments section, helps to remind you why you first took up science in the first place.

I hope that this brief summary of the nature of the geoblogosphere supports my case for its being of potential value. But discerning, selecting, and accessing that value is clearly up to the individual, and the scope of the geoblogosphere, modest though it is in a global context, is broad. How to sample and focus? First of all, Huber and his colleagues maintain a list of more than 250 geoblogs worldwide, and this can be found at http://geoblogs.stratigraphy.net/?action=list. But it’s a long list; some blogs are more active than others, some more serious and science-focused. For a quick review of who is writing about what, the associated aggregator, Geoblogosphere News (http://geoblogs.stratigraphy.net/?action=news) is ideal. The latest posts from every geoblog are listed as a title and opening words, together with a link to the blog.

I recognise that every individual structures their relationship with the internet differently, but I find that the most effective way of keeping track of blogs and news sites that interest me is through an overall aggregator – I use Bloglines, but there are various choices, all of them entirely free. This allows me to subscribe not only to the Geoblogosphere News, but to specific individual blogs and other sources. This is a “one click” solution to tracking activity – the aggregator simply lists the latest articles and I can follow up on whatever I wish, given whatever time is available. Furthermore, each blog whose content and style attracts an individual reader will generally include a list of blogs and resources that the writer follows – often a good shortcut to new sites of similar character and focus.

I realise that undoubtedly many Fellows of the Geological Society are not only aware of, but actively participate in, the geoblogosphere. But my purpose here is to try to spread the awareness of its value more broadly, for there is a clear geographical – and possibly cultural – imbalance, a statistical anomaly. The energy and activity of the geoblogosphere comes dominantly from the United Sates. More than half of the respondents to Geissler’s survey were based there; more writers responded from Spain and Germany than from the U.K. And this imbalance is also evident in audience statistics: here, I can only speak for the numbers relating to my own blog, but I suspect that they are fairly representative. While Through the Sandglass has been visited from over a hundred countries, U.S. readers account typically for half of the audience, those from the UK perhaps ten percent. Now it might be argued that these numbers are simply representative of the relative populations of the U.K. versus the U.S.; however, while population statistics of geoscientists per capita are difficult to find, the numbers of geosciences degrees awarded each year are not, and they point clearly to a higher concentration of geoscientists in the U.K..

So, if, as would seem to be the case, the level of representation, activity and interest in a valuable and informative communication tool is lower in the U.K. than in the U.S., why is this? As geoscientists in today’s world, we are surely concerned not only with the progress and vitality of our discipline, and communicating effectively with each other, but also with, for want of a better word, outreach. Who could dispute that any means of more effectively communicating how our planet works, how our science works, how we work, is worth exploring? I will not presume to answer these questions, but simply, through this article, hope to stimulate interest and discussion of the effective use of the geoblogosphere.

Oh, and might The Geological Society (not to mention society in general) benefit from its own blog?

Links:

The summary results of Lutz Geissler’s survey are available at http://www.geoberg.de/blog/geoblogosphaere-web-2-0/short-summary-of-the-geoblogosphere-survey-results-2009

Kim Hannula, whose blog is titled All of my faults are stress-related (but she is currently taking a break), has, together with Anne Jefferson, conducted an interesting survey on women geoscientists and blogs. The results were recently reported at the GSA Annual Meeting, and are summarised at http://scienceblogs.com/stressrelated/2009/12/women-in-geoscience_and_blogs.php

The GSA abstract of the paper is at http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_161556.htm

The UK representatives of the geoblogosphere that I have been able to identify (with apologies to those that I have missed) are:

http://daveslandslideblog.blogspot.com/

http://earthlearningidea.blogspot.com/

http://hypocentral.com/blog/

http://scienceblogs.com/highlyallochthonous/

http://volcanism.wordpress.com/

http://geologywestcountry.blogspot.com/

http://www.ethicalpalaeontologist.com/

http://bobjamieson.net/

http://throughthesandglass.com (my own)

Below is a very personal selection of the international English-language blogs that I follow which provides a sampling of the diversity of the geoblogosphere:

http://geology.about.com/

http://clasticdetritus.com/

http://www.earthmagazine.org/rss/index/Blogging_on_Earth

http://nvcc.edu/home/cbentley/geoblog/index.htm, now http://mountainbeltway.wordpress.com/ (Callan Bentley’s blog)

http://stories-in-stone.blogspot.com/

http://lrrd.blogspot.com/

http://suvratk.blogspot.com/

http://my.opera.com/nielsol/blog/

http://geology.com/news/

And finally, to illustrate the ways in which communicating research can be done through blogging, here’s a link to the geosciences category at Research Blogging:

http://researchblogging.org/post-search/list?tag_id=7

The Franklin Institute

 

Being volcanically marooned in Philadelphia, and the heavy lifting of furniture into our daughter's new apartment being essentially completed, what better way to spend a day than an excursion into the city? Our original destination was the planetarium at the Franklin Institute (a little more on that later), but there are many distractions in the city, and many within the museum. In the complex of institutions around the leafy (and, at this time of year, gloriously blossom-laden) Logan Square (a geometrically inaccurate name, since it's a circle) is the Free Library of Philadelphia. I had never visited it before and so we wandered in - literally, as anyone can. It's an extraordinary and uplifting institution, a vast library that is totally open to the public, its banks of computers and bookshelves clearly equally popular and appreciated by folk of all ages. The rare book collection can be visited simply by ringing the bell on its door. I have simply never seen a library like it and felt privileged to visit - it represents everything that a library should be.

The Franklin Institute, the city's science museum, was teeming and noisy with families and kids - again, an uplifting sight. Visitors are greeted by a truly gigantic statue of the man himself (it occurred to me that this was Philadelphia's Big Ben), with a changing selection of his "wise sayings" projected on the walls; we followed his advice that "an investment in knowledge pays the best interest," even in "the prime of senility." It's a great and diverse museum - and I was delighted to find sand scattered, so to speak, throughout. The "changing earth" exhibit contained an interactive stream table which, though clearly in need of sand nourishment (and only a poor relation of Steve Gough's Emriver models) was clearly popular, hardly a kid passing it by without swirling some sand around (and presumably unwittingly transporting a few grains home).

A poster on the wall nearby admirably stated the "When we know how rivers work, we can make them work for us." The "when we know" wording grabs the attention.

Elsewhere, a fine display declares that "No rock is forever" and nearby the visitor is invited to tilt two exhibits, one vegetated sand, the other barren, to illustrate how "Plants hold the earth together." The section on earthquakes contains pottery pieces retrieved after the San Francisco earthquake and fire to which sand has been fused. In the addictively interactive "Sir Isaac's Loft" section of the museum (how can you not play with the exhibits?) is a sand pendulum, for which there seemed to be a constant queue of kids of all ages.

 

      

Eventually, it was time for our original destination, the planetarium show. Neither of us has been to a planetarium in years, but remember the childish excitement and magic of those visits. We had selected the classic "sky tonight" show, since that was what stuck in the memory, rather than the undoubtedly more dramatic offerings on black holes and so on. It was highly enjoyable - and informative - but somehow the magic wasn't quite there. And then I realised why: it was entirely digital. A major part of the old experience was that enormous, complex, mysterious piece of equipment that took centre stage - the projector. Like something from an alien civilisation, that piece of kit was awe-inspiring, and its presence sorely missed.

The famous London Planetarium, the site of my childhood excitement that inspired generations of kids, was closed several years ago - attached to Madame Tussaud's, it now is devoted to shows about celebrities. Ben Franklin must be turning in his grave.

[The image of the Zeiss planetarium projector is from the Montreal planetarium, reproduced under a GNU Free Documentation License. The photo of Big Ben - I have no idea why I didn't take my own - is reproduced under a Creative Commons License courtesy of mrkathika's photostream on flickr.com.]