• The Mississippi: A Visual Biography by Quinta Scott

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Mardi Gras Pass: Keep it or Dam It

Mississippi River Ridge at Bohemia

While folks partied in the streets of New Orleans on Fat Tuesday, the Mississippi River gave the State of Louisiana a gift, a freebie. The river broke through the low ridge at Bohemia, south of the end of the Main Line levee, and began pouring sediment into Breton Sound to the east. The river is doing for free what the state would have the Federal Government pay $50 billion over 50 years to rebuild barrier island and to divert the Mississippi to Breton Sound on the east and the Barataria Basin on the west. State engineers already had a plan on the books to create a similar diversion into Breton Sound a mere mile from the Bohemia siphon, where the breach occurred.

Bohemia Siphon along the Mississippi

The site of the breech was the old, inoperable siphon, designed to deliver fresh water from the river to the wetlands in the sound. The siphon opens onto a spillway, created in 1924 as a means of relieving flooding in New Orleans. However, this spillway is 45 miles south of New Orleans. After the Flood of 1927 the Bonne Carre Spillway and the Achafalaya and Morganza Spillways were design to siphon water from a flood Mississippi before it reached New Orleans.

Sites of Bohemia Siphon and the Oil Facility on the End of the Road on the Mississippi Ridge

Now the U.S. Army Corps of Engineers has given Houston-based Eland/Sundown Energy permission to seal the crevasse, dam it in order to rebuild the road to their work facility not more than two or three miles down the road, where it ends at a gate to its yard.

Right now the Mississippi is low, very low and the spillway is delivery fresh water and sediment at a much slower rate than the 50,000 cubic feet per second the state-designed spillway would flow. But water and sediment is flowing to Breton Sound. It is a gift from the Flood of 2011. The river will rise again, flood, and spill more water through the breach, enlarging it and sending more water and sediment to the Bohemia Wildlife Management Area and Breton Sound.

Breton Sound at the Bohemia State Wildlife Management Area just off Pointe a la Hache

In 2005 Katrina roared across the Mississippi south of the siphon, and tore north through Breton Sound and Lake Borgne tearing up the wetlands and busting through the levees that protected St. Bernard Parish, trashing the towns there. Then it tore across the wetlands that protects that lovely string of towns on the the State of  Mississippi coast–Bay St. Louis, Pass Christian, Gulf Port, and Biloxi–and destroyed them. Had those wetlands in Breton Sound been in tact, Katrina would not have been as devastating. Never mind what happened after it arrived in Lake Pontchartrain, washed into the canals that drain every drop of water that falls on New Orleans, and collapsed the levees that contained them, flooding the city.

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Tap the Mississippi to Relieve the Parched West and the Colorado River

Colorado River runs through the Grand Canyon near Peach Springs, Arizona

The Colorado River is tapped out. So the Bureau of Reclamation and the people who live in the Colorado Basin are eyeing the Mississippi to relieve some of the demands we have put on the Colorado.

The Bureau of Reclamation?: Think the Corps of Engineers for the western states. While the job of the Corps of Engineers is to control flooding on the Mississippi and its tributaries, the job of the Bureau of Reclamation is get water for drinking and irrigation to the parched states west of the Great Plains. It also provides hydroelectric power to those states. Where the Corps of Engineers manages the Mississippi, the Bureau of Reclamation manages the Colorado and the Columbia.

To get water to all those farmers and electricity to all those cities it has dredged canals and constructed dams and power plants. It has also allowed the sparsely settled west of the early 20th century grow into the densely populated cities of the 21st. All those people and all those farmers need water to irrigate their lawns and their vegetable crops and to light their cities. Actually, the farmers are competing with the city dwellers for water and when push comes to shove the farmers lose.

Lake Mead

It took 19 years to fill Lake Mead, upstream of the Hoover Dam, to 24 million acre-feet. Between 1998 and 2007, Lake Mead, which serves Las Vegas and its surrounds, lost 54% of its water.

Lower Mississippi at Riddles Point, Missouri south of the Ohio

One solution is to tap the Mississippi River just below its confluence with the Ohio and send the water to the Navajo River in southwest Colorado through a 775 mile=long pipe 144 inches in diameter. From their it would flow to the San Juan River, a tributary of the Colorado. Agricultural users in Colorado, Arizona, and New Mexico would cease their demands on the Colorado, leaving it free to serve the cities. The history of the Corps of Engineers’ interventions on the Mississippi River is the story of the law of unintended consequences.

To repeat what I have written before in The Mississippi:

“Artificial levees, extending clear to the Gulf of Mexico, may have made human habitation of the delta south of Cape Girardeau possible, but prevented the Mississippi from refreshing its marshes with its sediment when it did flood. Revetments built of concrete mats may have stabilized the navigation channel, but reduced erosion of the banks, a source of sediment in the marshes. James Eads’ jetties at the mouth of the river may have allowed the river to cut a thirty-foot navigation channel through the sandbar blocking the South Pass of the modern delta, but delivered sediment carried by the river to very deep water at the continental shelf, where it washed away, never to be used for marsh building. Closure of the old distributaries of the river may have prevented flooding in the bayou country of Louisiana, but cut the flow of Mississippi sediment to the coastal marshes. Channel dams may have made navigation on the Upper Mississippi profitable, but they retained its sediment north of Alton, Illinois. Dams on the Missouri, from which the Mississippi drew sixty percent of its sediment, did the same. In short at the beginning of the twenty-first century, the coastal marshes south of New Orleans received eighty percent less sediment than they had at the beginning of the twentieth and eroded away.”

According to Amy Joi O’Donoghue, who had written an excellent series of articles in Deseret News, which is published in Salt Lake City, folks in Utah and other states served by the Bureau of Reclamation look at the Flood of 2011 and say the Mississippi has more water than is needed in the Midwestern and Southern states that border it.

Breton Sound: Bohemia Wildlife Management Area

But the Louisiana coastal marshes, particularly those in the Barataria Basin and Breton Sound, need the fresh water and mud that the Mississippi delivered to the Gulf of Mexico during floods like that of 2011 to rebuild its wetlands and protect its cities, including New Orleans. The cities along the Mississippi Gulf Coast, which were wiped out during Katrina, could also use some solid wetlands out front in the Gulf of Mexico. During the BP Flood of Oil in 2010, freshwater flowing out of the Mississippi helped push some of that oil away from the wetlands.

Barataria Basin: Fresh Marsh, Jean Lafitte National Historical Park, Barataria Unit

So yes, we in the Mississippi River Basin occasionally have way too much water, but tapping the Mississippi year after year, flood or drought, could have the kind of unintended consequences that building the levees had and that constructing the dams on the Missouri had on the Louisiana Coast.

The time is fast approaching when we Americans are going to have to sort out how we manage freshwater, be it in the Mississippi Basin or in the Colorado Basin and other western river basins.

The Mardi Gras Diversion at Bohemia

The Mississippi Ridge at Bohemia south of the end of the main line levee

On February 28, New Orleans partied at Mardi Gras, the Mississippi broke through the Mississippi ridge and created a crevasse at the Bohemia Spillway, a couple of miles south of the end of the Main Line Levee, and began delivering precious fresh water and sediment to Breton Sound, which has experienced extreme losses of marshland.

It’s a gift and we can thank the Flood of 2011 for it. All that stood in the way of the crevasse was a slightly elevated gravel road, which the flood washed away last summer. Below are two captions that I cut from The Mississippi: A Visual Biography.

As you will see below, the crevasse represents a potential savings of $6.4 million, if the Corps of Engineers and the Louisiana DNR were to do the work. What the river did by itself may need tidying up, but that work can be done by the Corps and the DNR.

 

Breton Sound at the Bohemia State Wildlife Management Area just off Pointe a la Hache

Mississippi River Ridge: Pointe a la Hache Relief Outlet

Plaquemines Parish, Louisiana

“It is remarkable, that the banks of the river are much more elevated than the circumjacent country. This is occasioned by a more copious deposition along the margins, than at a distance from them. These are thickly covered with grass, and a vast variety of ligneous plants, which serve to filtrate the waters in their progress to the low grounds and swamps, and to retain the greatest proportion of the alluvious substances. Hence the lands along the banks to a certain depth, generally from four hundred to seven hundred yards are excellent for tillage; while the whole surface in the rear of them, extending to the sea, is alternately covered by lakes and impassable swamps.”–Major Amos Stoddard, 1812[i]

The 2004 Louisiana Coastal Area proposal emphasized diverting freshwater and sediments into Breton Sound. So did Louisiana’s post-Katrina 2007 Comprehensive Master Plan for a Sustainable Coast. So did the Corps of Engineers’ post-Katrina proposal. So did numerous unofficial proposals. At the two-year anniversary of the storm, other diversions south of the Caernarvon structure, actual and planned, directed freshwater into Breton sound.

The White’s Ditch siphon, not far from Caernarvon, diverted small amounts of freshwater into northern Breton Sound. The mainline levee ended at Bohemia, where the river was also free to sluice down the Bohemia spillway, but only when it ran high. Built in 1926, the spillway was non-operational by 2005. The Pointe a la Hache relief outlet ran from Bohemia south to the Ostrica Lock. Here, only the natural levee and a gravel road lay between the Mississippi and the marshes in southern Breton Sound. A young natural levee forest had taken root on the ridge. A flooded Mississippi could spill over the levee and wash into the adjacent marshes, or maybe it couldn’t. The gravel road may have impeded overbank flooding. Further south, near Point Pleasant, the Bohemia diversion structure and spillway could have diverted water into Breton Sound through Bayou Lamoque the same rate as Caernarvon, was inoperable, but was included in Louisiana’s 2007 plan for a sustainable coast. At the beginning of the twenty-first century, how much fresh water the overbank flooding introduced into southern Breton Sound had not been measured, nor had any changes in water quality caused by the flooding.

In 2001 the Corps of Engineers and the Louisiana Department of Natural Resources began design work on a diversion at Fort St. Philip, on the east bank opposite Fort Jackson. The agencies planned to divert water from the river at the rate of 2,500 to 5,000 cubic feet per second into 2,252 acres of deteriorating wetlands and open water near the site of the old fort. The existing marshes graded from fresh at the toe of the ridge to saline. The site, short on development and infrastructure, presented a rare opportunity to rebuild marshes in shallow estuarine waters.

Engineers would cut a series of gaps in the bank of the river, armor them, creating channels that would carry river water and sediment to open water adjacent to the natural ridge of the river. Farther downstream they would create a diversion outfall channel, which would connect to Fort Bayou. Holes punched in the outfall channel would allow water and sediment to leak into the shallows between the bank and the bayou. The bayou would carry water and sediment to the east beyond the reach of the channel. The Corps and the DNR expected to create and 624 acres of marsh over the life of the project, recreate the progression of wetlands from natural levee to emergent marsh to mudflats, and reduce the loss of marsh in the rest of the site. The expected cost was $6.4 million. A final note: The Corps and the DNR suspected that the introduction of freshwater into marshes that were largely saline would disrupt existing oyster leases. And, the siltation the engineers hoped for might plugged oil and gas canals and disrupt access to the project area.

The coastal scientists and engineers who published the Comprehensive Recommendations Supporting the Use of the Multiple Lines of Defense Strategy to Sustain Coastal Louisiana in August 2007 recommended encouraging the Mississippi to wash over its banks, a rates totaling up to 100,000 cubic feet per second, over the twenty miles south of Bohemia. Doing so would rebuild its natural levee. It was a habitat that, in the twenty-first century at least, was unique to Louisiana, where all other ridges were under intense development. The process would offer scientists and engineers an opportunity to observe and understand how a river develops its natural levee.[ii] Photograph 2007

 

Bohemia Siphon along the Mississippi

 

Mississippi River Ridge: Small Siphon at Bohemia

Plaquemines Parish, Louisiana

James Buchanan Eads solved the problem of sandbars blocking the passes at the mouth of the Mississippi with jetties, which opened Southwest Pass to shipping, but as early as 1832 Major Benjamin Buisson, Chief Engineer of the State of Louisiana, proposed and the State Legislature approved dredging a canal to connect the River at Fort St. Philip to Breton Sound. The State sent the proposal to Congress, which ordered a survey in 1837. Major W.H Chase did the survey and presented the War Department with a plan for the canal at an estimated cost of ten million dollars, a price tag that was way beyond Congress’s reach for public improvements in 1837.

Mr. R. Montaigu, a civil engineer, revived the idea twenty years later, but it was not until 1871 that Congress ordered the Corps of Engineers to make surveys and plans for the canal. Major C.W. Howell drew up the plans and a board of army officers, that included Major Howell, made a report that favored the plan over Eads’ proposed jetties in 1873. The cost would be thirteen million dollars. General A.A. Humphreys, Chief of Engineers and Eads’ rival, approved the plan, but General J.G. Bernard dissented, saying the cost estimates for the canal were unreliable, the canal would not solve the problem, would not be finished until 1884, and at least one of the passes in the river should be improved. And, should South Pass be jettied, it would function like a canal.

In February 1874 Eads proposed delivering a channel twenty-eight feet deep and 350 feet wide at a cost of ten million dollars, and he offered to work for free until he had achieved a channel twenty feet deep when he would receive a million dollars and a million for every two feet until the channel reached twenty-eight feet. The rest, five million dollars, would go for maintenance.[iii]

Eads got the job and got the job done. His jetties and those that followed delivered sediment to very deep water, where it was useless for land building. Combine the jetties with the levees and the wetlands in the Barataria Basin to the west and Breton Sound to the east were starved for freshwater and sediment.

In the wake of Katrina the canal was back and Fort Philip, located south of the end of the mainline levee and already the site of a planned diversion, was the proposed site of a major diversion of freshwater and sediment to Breton and Chandeleur Sounds.

First, the diversion: In 1994 Ivor van Heerden proposed diverting Mississippi water and sediment to Breton and Chandeleur sounds through the Bohemia Wildlife Management Area near Fort Philip and creating a new delta. He reiterated the proposal in a 2003 paper and again in his 2006 book, The Storm. The diversion would be huge, 200,000 cubic feet per second, would create more than five thousand acres or eight square miles of wetlands every year, leading to 140 square miles of new land within twenty years. The Bird-foot Delta would be abandoned, though enough water would be left the river to maintain the shipping channel through Southwest Pass. Or, a new navigation channel would be dredged just north of Empire through Adams and Bastian Bays in the Barataria Basin to the Gulf of Mexico. A new lock and other control structures would have to be built to make it possible. The delta would evolve into a series of barrier islands, which would coalesce with the Breton and Chandeleur islands to the east and the Barataria Bay islands to the west, and create a continuous arc of islands from Grand Isle to the northeastern tip of the Chandeleur Islands, a speed bump to hurricane storm surges. The new wetlands would further reduce storm surges. New Orleans’ levees would be protected. Eventually, the new delta would extend across MRGO, leading to its closing, but after Katrina that was on Louisiana’s agenda anyway. The proposal followed van Heerden’s dictum: “Barrier islands protect the wetlands, the wetlands protect the levees, the levees protect the home.” Photograph, 2007

 


[i]      Stoddard, 159.

[ii]             Multiple Lines of Defense Assessment Team, “Comprehensive Recommendations Supporting the Use of the Multiple Lines of Defense Strategy to Sustain Coastal Louisiana,” Lake Pontchartrain Basin Foundation, August 17, 2007, 71-72, http://www.saveourlake.org/pdfs/JL/LPBF%20-%20CRCL%20Final%20Draft%20MLODS%20report%208-17-07%20for%20release%20part1.pdf; Lane, Robert R., John W. Day, Jr., Burnell Thibodeaus, “Water Quality Analysis of a Freshwater Diversion at Caernarvon, Louisiana,” Estuaries, Vol. 22, No. 2A, June 1999, 329, http://estuariesandcoasts.org/cdrom/ESTU1999_22_2A_327_336.pdf; Louisiana Coastal Wetlands Conservation and Restoration Task Force, Delta Building Diversion North of Fort St. Philip (BS-10), October 2003, http://data.lacoast.gov/reports/gpfs/BS-10.pdf.

[iii]             Corthell, Elmer Lawrence, A History of the Jetties at the Mouth of the Mississippi River, New York: John Wiley & Sons, 1881, 17-23; Barry, 68-71;

About Oysters, Tidal Exchange, Fresh Water Diversions, and the BP Gusher in Barataria Basin and Breton Sound

Oysters, U.S. Fish and Wildlife Service Photo

The muscle that keeps its bivalve shells tightly closed relaxes, opens, and the American oysters feeds, filtering algae and plankton out of huge quantities of brackish water. Oysters start spawning in the Gulf of Mexico when the water temperature reaches sixty-eight degrees and increase their production at seventy-seven degrees. The males release their sperm into the water. When the sperm enter the females water transport system, they spawn, producing between twenty-three million and eighty-six million eggs depending at their size and age. And, they spawn several times in a season, which in Louisiana goes from March to November and peaks in late May, June, and September.

The eggs hatch six hours after fertilization and the larvae drift in the water column for two or three weeks, feed on plankton, and evolve through several stages into juveniles. Juveniles crawl in a circular pattern using a single foot, searching out a solid surface on which to attach themselves and live out their lives. Sand will do, but something harder, like other oyster shells, is better. Once settled they squirt a droplet of liquid cement from a pose in the foot, lose the foot, become spat, and develop their shells. They become sexually mature in four weeks.

Temperature, salinity, tides, turbidity, and food influence their rate of growth. Adults tolerate a salinity range of two to forty parts per thousand. In the Gulf of Mexico they do best at twelve to thirty parts per thousand. Too much salt, they grow too fast, and fail to reproduce. Freshwater can kill them.

The nooks and crannies of the hard surface of an oyster reef are the ideal habitat for small marine animals–grass shrimp, mud crabs, red beard sponge, hooked mussels, oyster drills, and barnacles–food for red drum, speckled trout, croaker, and blue crab. The anglers follow.[i]

In order to push back on the encroaching oil for the BP’s Deepwater Horizon gusher of oil heading into Breton Sound and the Barataria Basin, Louisiana opened wide the freshwater diversions into the basins, at Caernarvon into Breton Sound and at Davis Pond into the Barataria Basin. The oysters died from these massive inputs of freshwater.

Pelicans await fish diverted from the Mississippi along with freshwater in the Caernarvon Outfall Canal at the head of Breton Sound

In the old days, before the Corps of Engineers ran the Mississippi levees clear down the west bank to Venice and down the east bank to Bohemia, the Mississippi overflowed its banks almost yearly and poured freshwater into the Barataria Basin on the east and Breton Sound on the west. The freshwater pushed out salt water that had crept in on gulf tides during the fall and winter, when the river stayed within its banks. This is the principle of tidal exchange.

Really big floods killed the oysters  the first year, but the bi-valved critters bounced back in the following years. When you understand their reproduction cycle, you understand how that is possible.

In 1814 a century after the French settled New Orleans, the brackish marshes, where oysters thrive began creeping inland in Breton Sound. Little bit by little bit, it was a slow creep inland, even after the big levees were constructed after the Flood of 1927. With the brackish marshes creeping inland, Louisiana built the first small freshwater diversions into Breton Sound in 1926 to push back salt water and increase oyster production.

After 1960, the pace picked up. Gas and oil companies, dredged access canals through the marshes, tossed their dredge into spoil banks that lined the canals, and introduced salt water into intermediate and fresh water marshes. Canals that ran north and south conveyed salt water into the marshes on the tides. Canals that ran east and west stopped the flow of water south. Marshes to the north of the spoil banks drowned; those to the south starved for water. The big tall levees prevented the Mississippi from streaming freshwater into the basin to counter the salt water.

By 1988 the brackish marshes almost reached Caernarvon at the head of the sound. First, the oysters followed the brackish marshes north. Then, they died. Too much salt in the water. By 1990 salt water had destroyed 50,000 acres of private oyster beds.

Louisiana designed the Caernarvon Freshwater Diversion Structure to push brackish marshes south and revive the oyster industry in Breton Sound. Louisiana built the Davis Pond Diversion Structure in Barataria Basin with a similar intent, push salt water out.

So the question we must ask ourselves, which is worse: freshwater killing the oysters, which will produce well next year or the year after next when the salt water creeps in on the tides and reestablishes the salinity, or oil fouling the oyster beds and who knows when they will come back?

Update, July 21: The New York Times weighed in on the plight of the oysters.

Copyright, Quinta Scott, 2010, Words and images, All Rights Reserved


[i] Stanley, Jon G., Sellers, Mark A., Species Profile: Life Histories and environmental requirements of coast fishes and invertebrates (Gulf of Mexico)–American Oyster, U.S. Fish and Wildlife Service Biol. Rep 82(11.64) U.S. Army Corps of Engineers, TR EL-82-4, 1-13, http://www.nwrc.usgs.gov/wdb/pub/species_profiles/82_11-064.pdf

Breton Sound and the Oil Slick

Extent of Oil Slick in the Gulf of Mexico, April 29, 2010On April 29. The MODIS image on the Terra satellite captured a wide-view natural-color image of the oil slick (outlined in white) just off the Louisiana coast. The oil slick appears as dull gray interlocking comma shapes, one opaque and the other nearly transparent. Sunglint -- the mirror-like reflection of the sun off the water -- enhances the oil slick’s visibility. The northwestern tip of the oil slick almost touches the Mississippi Delta. Credit: NASA/Earth Observatory/Jesse Allen, using data provided courtesy of the University of Wisconsin’s Space Science and Engineering Center MODIS Direct Broadcast system.

Tentacles of the the Oil Slick reach towards Pass a Loutre WMA at the End of the Bird Foot Delta of the Mississippi River, April 29, 2010. On April 29, the MODIS image on the Terra satellite captured a wide-view natural-color image of the oil slick (outlined in white) just off the Louisiana coast. The oil slick appears as dull gray interlocking comma shapes, one opaque and the other nearly transparent. Sunglint -- the mirror-like reflection of the sun off the water -- enhances the oil slick’s visibility. The northwestern tip of the oil slick almost touches the Mississippi Delta. Credit: NASA/Earth Observatory/Jesse Allen, using data provided courtesy of the University of Wisconsin’s Space Science and Engineering Center MODIS Direct Broadcast system.

The images from NASA show the extent of the Oil Slick as of April 29. The graphic from NOAA show the extent of the Oil Slick between April 25 and April 29, and projects its extent on April 20, when it is expected to creep into the Pass a Loutre WMA, then into Breton Sound, and finally engulf the the Chandeleur Island and the Breton NWR. If it invades Breton Sound, my guess it will also reach into the Delta NWR, which lies between the Mississippi and the Sound.

Graphic from the National Oceanic and Atmospheric Administration, showing the Extent of the Oil Slick between April 25 and April 30, 2010

Beginning in the fall of 2006 and continuing through the fall of 20o7 (really a small amount of time considering the enormity of the issues facing the coastal wetlands) I made five trips to the Louisiana coast, delving deeper and deeper into the deterioration of its wetlands and our attempts to restore them.

At the beginning of last year, when I decided to devote this blog to all things Mississippi River, I decided I would respond to news with history. That is what my book, The Mississippi: A Visual Biography is about, the history of the Mississippi River and the wetlands it created, how they were formed, what we have done to change them, and how we are trying to manage the river and wetlands we have created.

I came away from the experience of photographing, researching, and writing the book as a generalist on the Mississippi and its wetlands, not as an expert on any one portion of the river, but as the rare person who has looked at the river as a whole. The oil leak, such an inadequate description of the rupture of this mile-deep oil well, in the Gulf of Mexico brings home to me the limits of my expertise on the river.

Nevertheless, I shall do what I said I would do: Respond to news with history, this about Breton Sound and oysters:

Breton Sound at the Bohemia State Wildlife Management Area just off Pointe a la Hache

The Mississippi and the Gulf of Mexico performed their annual two-step year after year, exchanging freshwater for salt in the Breton Sound estuary: Saltwater streamed into the basin on gulf tides in the late fall and early winter; during its spring rise the Mississippi flooded the basin with freshwater and sediment and flushed out saltwater. In the 1930s the Corps of Engineers ran their flood protection levees down the west bank of the Mississippi to Bohemia. From then until 1991, when the Louisiana Department on Natural Resources opened the Caernarvon Freshwater Diversion Structure, Breton Sound depended on rainfall for freshwater.

Beginning in 1812 brackish marshes in Breton Sound moved inland, just a little bit between 1812 and 1960. After 1960 the pace of movement sped up. Oil and gas  companies dredged numerous canals that crisscrossed the region, gobbled up 8,256 acres of marsh, extended to the gulf, changed the water flowed through the marshes, and allowed saltwater into fresh and intermediate marshes. Erosion increased to 270 acres a year.

In 1965 Hurricane Betsy washed in saltwater and destroyed the forested wetlands in the backswamp of the Mississippi natural levee close to the head of the sound, turning the area to open water. By 1986 brackish marshes with a salinity of five parts per thousand reached clear north to the Big Mar, an impoundment just off the Mississippi at Caernarvon.

Oysters moved inland with the marshes. By the late 1980s the rising levels of salinity and disease in Breton Sound were killing the oysters. Black drum and conch, saltwater predators, feasted on them. By 1990 saltwater had destroyed 50,000 acres of private oyster beds, which ringed the southern rim of the marshes and followed marshes off the east bank of the Mississippi. Oysters and levels of salinity have been an issue in Breton Sound ever since Slavonian immigrants found an abundance of oysters east of the Mississippi in the 1840s.

Louisianans began discussing the need for freshwater diversions through their levees as early as 1900. They first considered diverting Mississippi water into Breton Sound in 1914 to restore oyster beds. Each flood brought levee breaks that killed the oysters in the first year, but boosted production in the following years. Beginning in 1926 the State tapped the Mississippi with small siphons designed to increase oyster production. In 1955 oysters farmers in Breton Sound requested a freshwater diversion. Four years later the U.S. Fish and Wildlife Service informed the Corps of Engineers that diversions would be advisable. Congress authorized diversions in 1965 and held public hearings in 1968 and 1969, when a diversion at Caernarvon was proposed. For a dozen years the State, the Corps, Fish and Wildlife, and oyster farmers discussed the pros and cons of a diversion. In 1982 the State signed on.

Caernarvon Marshes, Dominated by invasive water hyacinth.

In 1986 Congress authorized a freshwater diversion structure to be built at the Caernarvon crevasse, located just short of the English Turn on the Mississippi fifteen miles south of New Orleans. It was at Caernarvon that the City of New Orleans blasted a crevasse on May 9, 1927 in the levee that released floodwaters from the flooded Mississippi to take pressure off its levees, and save the city from a levee break. The purpose of the new diversion was to reduce salinity in Breton Sound and to increase habitat for fish and wildlife, including nutria and muskrat for the fur trade. Over the years Louisianans put more and more demands on Caernarvon as they learned how to use this new reconstruction tool and recognized its possibilities.

In February 1991 the Corps of Engineers and the Louisiana Department of Natural Resources opened gates in the five fifteen-foot square culverts of the Caernarvon Freshwater Diversion Structure for the first time and released freshwater, sediment, and nutrients into an outfall channel. The Corps designed the structure to flow at the rate of 8,000 cubic feet per second. The intent of the project was to control salinity in Breton Sound, preserve 16,000 acres of marsh, and benefit an additional 77,000 acres of marshes and bays. It must be noted that Congress did not authorize Caernarvon for marsh creation, but rather for salinity reduction. Marsh creation, it seems, was a by-product.

Over the years the DNR changed the operations plan of the diversion structure. At first the agency operated the structure to maintain the salinity of the state oyster seed grounds. For three years in 1994, 1995, and 1996 the DNR kept the gates in the structure wide open during the winter to maximize the amount of sediment pouring into the outfall region and to nourish marsh vegetation. Its third plan provided more consistent patterns of salinity at the five parts per thousand line, which had been pushed south to the northern edge of 1986 oyster leases. The fourth sent high and low pulses of water into the marshes during the spring to mimic actual flooding, to hasten the marshes’ recovery after Katrina and to manage the five parts per thousand salinity line.

By 1998 freshwater marsh plants increased seven-fold in the first seven years. New marshes increased by 406 acres and fresh marsh appeared in the vicinity of Big Mar and around Lake Lery to the east. Salt marsh plants decreased by fifty percent. The basin’s rate of sedimentation kept pace with sea level rise.

As salinity levels dropped, anglers caught twice the largemouth bass. Upward of 25,000 ducks descended on the marsh to winter. Muskrats and alligators built nests, muskrats by the thousands, alligators by the tens. When a red tide threatened Breton Sound in 1996, the Corps of Engineers suspected it was the freshwater diversion that held it back. The new marsh removed nitrogen from the water before it reached the Gulf of Mexico. So did the exploding population of new oysters, which increased from close to zip to thousands. White shrimp increased, but brown shrimp declined, so did the number of blue crabs and red fish. Speckled trout remained about even. All this occurred with no fish kills, no algal blooms, and no decrease in water quality.

When Katrina made landfall at Buras, Louisiana and crossed the Mississippi into Breton Sound, the sound took a big hit.

Katrina’s winds and surging waters ripped across the fresh marshes to the southwest of Caernarvon, sheared them down to the root mat, pushed them up into accordion pleats, and then skidded them across the basin until they hit the elevated ridges–levees, natural levees, and spoil banks–and deposited them there. The winds rolled the marshes into balls, and tossed them into trees or scattered them across shallow ponds–newly created areas of open water.

When Katrina departed Breton Sound, the hurricane left behind forty-one square miles open water, ninety percent of it in fresh and intermediate marshes created by freshwater diversion in the northwestern part of the basin. In some places the water was more than three feet deep. But, for the most part, water skimmed mud flats. It was hoped that the marsh balls, made up of buoyant organic soils, would anchor in the mud flats and reestablish the marsh. Once the Louisiana Department of Natural Resources repaired the diversion structure, the agency opened the gates wide to deliver freshwater and sediment of the most heavily damaged areas.

Mississippi River Ridge at Cane Ridge Slough

In the Spring of 2006 U.S. Geological Survey Landsat maps displayed the areas of open water and new growth in the northwestern portion of Breton Sound. Trees along the Mississippi natural levee were leafing out. So were trees along the Cane Bayou Ridge and the River aux Chenes ridge to the south. Some marshes were recovering between the Caernarvon outfall canal and the north shore of Lake Lery. But the site of the changes in outfall management, the region southwest of Big Mar, looked dead. That all changed by September. The marshes, closest to the outfall management area, those along the Mississippi ridge and those surrounding Lake Lery, were thriving, even though the river was running so low that little water and sediment got to the wetlands. To the south along River aux Chenes and directly west of Bayou Terre aux Boeufs, there was little recovery.Marshes at Delacroix along the Bayou Terre aux Boeufs Ridge

Congress looked at the land loss projections in light of Katrina’s damage to the Caernarvon wetlands and voted to spend $10.1 million dollars to modify the way the Caernarvon project works. Most of the sediment pouring through the gates ended up in Big Mar, not in the wetlands downstream. To deliver more sediment to the marshes, the Corps of Engineers would dredge sediment from the river and run it through a pipeline threaded through the diversion structure to the wetlands. This would add sediment to the region even in years like 2006 when the river ran low. Excavators would deliver dredge through the structure to areas in the wetlands where sediment was most needed. Scientists suggested doing just that at a plan formulation workshop in June 2006. And, they added that the Caernarvon structure could be used to divert freshwater through Bayou la Loutre.[i]

Pelicans await fish diverted from the Mississippi along with freshwater in the Caernarvon Outfall Canal at the head of Breton Sound

Here we are five years later, and it looks like Breton Sound and its oyster beds and fisheries will take another great hit. LaCoastPost has links to articles, which state that Louisiana officials have open the Caernarvon diversion structure and its twin the Davis Pond diversion structure, which diverts freshwater to the Barataria Basin on the west side of the Mississippi, in order to flush freshwater through Breton Sound and the Barataria Basin to counter in influx of oil-laden saltwater into the wetlands.

Update: LaCoastPost has in its May 1st update on the oil slick a map from the New York Times, indicating that the oyster beds in Breton Sound have been closed to harvesting in anticipation that the BP oil slick will foul the beds.

Update: There is a web site refugewatch.org that covers how the U.S. Fish and Wildlife Service is handling the oil that is or may wash into any one of the twenty-five refuges in the five state that line the American shoreline of the Gulf of Mexico. As of May 21, the service is restricting air flights over Breton Island in Breton Sound in order to leave nesting birds in peace.


[i] Day, John W., Jr., et al, “Restoration of the Mississippi Delta: Lessons from Hurricanes Katrina and Rita,” Science,  Vol. 315, March 23, 2007,  1680, http://www.clear.lsu.edu/clear/web-content/Web_items/Science%20Paper.pdf; Barres, John, and James B. Johnston, USGS Reports Latest Land-Water Changes for Southeastn Louisiana,” U.S. Geological Survey, no date, http://www.lca.gov/images/Land%20Water%20Changes%20for%20SE%20LA.pdf; U.S. Geological Survey, “Landsat Thematic Mapper 5 and 7 Satellite After Katrina Images, Caernarvon Area, September 26, 2005, http://www.nwrc.usgs.gov/hurricane/images/katrina/post-katrina-caernarvon-l.jpg; Barras, John, “Caernarvon Diversion Post-Katrina, Illustrating Some Recovery after Spring Flows from the Caernarvon Diversion,” in Lopez, John, “Hurricane Protection: Where Do We Stand?,” Powerpoint to the Tulane Engineering Forum, May 11, 2007, 11, http://tef.tulane.edu/presentations/lopez_john.pdf; Scheifstein, Mark, “Land Lost: Hurricanes Katrina and Rita turned 217 square miles of coastal land and wetlands into water,” New Orleans Time-Picayune, October 11, 2006, http://www.nola.com/recovery/t-p/index.ssf?/recovery/articles/land_lost.html ; U.S. Army Corps of Engineers, New Orleans District, “Louisiana Coastal Protection and Restoration, Enclosure G, Plan Formulation Workshop Report,” June 2006, Prepared by Brett Boston and Vern Herr, Groups Solutions, Inc., G-36, http://lacpr.usace.army.mil/PreliminaryReport%5CEnclosure%20G.pdf.

Ecosystem Restoration as Infrastructure–MRGO, Part 1

 

MRGO and its Spoil Bank Runs between Lake Borgne and Breton Sound

MRGO and its Spoil Bank Runs between Lake Borgne and Breton Sound

 

In 1965 the U.S. Army Corps of Engineers completed the Mississippi River and Gulf Outlet, a deep draft navigation designed to shorten the distance between the Port of New Orleans and the Gulf of Mexico. At completion it was 650 feet wide and 36 feet deep. The sides of its channel sloughed off into the bottom. By 2005 the wake generated by Ocean-going ships had widened MRGO’s channel to 2,200. The Corps of Engineers spent $22 million a year to maintain the depth of its channel, which had been increased to 40 feet.

 

MRGO at Shell Beach

MRGO at Shell Beach

 

 

MRGO extended 76 miles into the wetlands southeast of New Orleans, cut through the cypress swamps that protected New Orleans, shredded brackish and saline marshes that slow down and reduce storm surges, broke through ridge created by Bayou la Loutre, a speed bump for hurricane storm surges, and the hydrologic barrier between Breton Sound and Lake Borge, ripped up submerged vegetation that anchored the floor of marshes west and south of Lake Borgne, and coverted 20,000 acres of wetlands to open water and had a negative impact on another 618,000 acres.

 

MRGO Spoil Bank

MRGO Spoil Bank

MRGO Spoil Bank and Hurricane Levee: Shell Beach

St. Bernard Parish, Louisiana

The MRGO spoil bank: It’s six-tenths of a mile wide, wide enough to support a live oak forest at Shell Beach, but too exposed to open water to protect the hurricane levees of St. Bernard Parish.

When the Corps of Engineers dredged MRGO, excavators cast their spoil to the south side of the channel, building a wide spoil bank that filled all of Turiano, Grass, Nicks Lagoons, and part of Portman Lagoon, all near Shell Beach, and all a part of the 27,600 acres of estuarine wetland and lagoon habitat lost to open water and spoil. This is the mid-section of Reach 2 of the channel. This is the reach that cut through the Breton Sound Marshes, the natural levees of Bayou la Loutre and Bayou Yscloskey, and the cypress swamps that protected New Orleans. 

The Corps of Engineers constructed the St. Bernard Parish hurricane protection levee, part of the Lake Pontchartrain and Vicinity Hurricane Protection Project, of highly erodible sediment dredged from the channel, set it right out of the edge of the spoil bank. 

On the eve of Katrina sandy core of the levee offered no defense to the storm surge raging in from Lake Borgne. Parts of the levee reached the intended 17.5 feet, much of it was unfinished and reached only 15.5 feet or even 13.5 feet. The Corps of Engineers constructed the levee in stages, and waited for the soils to dry and settle before moving on to the next stage. The engineers completed the third stage in 1994-1995 and were waiting for funding from Congress for the final stage, which would have brought the levee to 17.5 feet. This is what faced Katrina’s storm surge, long, tall waves that plowed across Lake Borgne, breached the levee in many, many places, ripped across the declining wetlands, overtopped the back levee, and flooded St. Bernard Parish.

In January 2006 the Working Group for Post-Hurricane Planning for the Louisiana Coast ruminated on spoil banks and levees in their publication of that month. The “V” formed by spoil banks and levees of the MRGO and Intracoastal Waterway funneled the storm surge out of Lake Borgne into the Lower Ninth Ward and New Orleans East via the Industrial Canal. The straight spoil banks along oil and gas canals cut through meandering bayous, stop the sheet flow of water through the marshes, capture freshwater that might nourish the marshes, and send it directly toward the gulf. The spoil banks of navigation canals, like MRGO and the Houma Nav deliver saltwater to fresh wetlands, killing them.

But, what if we could analyze the effects of these artificial canals and ridges and incorporate them into coastal planning. 


          Day, John, Mark Ford, Paul Kemp, and John Lopez, “Mister Go Must Go: A Guide for the Army Corps’ Congressionally-Directed Closure of the Mississippi River Gulf Outlet,” Environmental Defense Fund et al., December 4, 2006, http://www.environmentaldefense.org/documents/5665_Report%20-%20Mister%20Go%20Must%20Go.pdf; Seed, R.B., et al., Investigations of the Performance of the New Orleans Flood Protection Systems in Hurricane Katrina on August 29, 2005, Berkley, California: University of California at Berkley, July 31, 2006, (2-6)-(2-7), http://www.ce.berkeley.edu/~new_orleans/report/CH_2.pdf; Working Group for Post-Hurricane Planning for the Louisiana Coast, A New Framework for Planning the Future of Coastal Louisiana after the Hurricanes of 2005, Cambridge, Maryland: University of Maryland, Center for Environmental Science, January 26, 2006, 17-18, http://www.umces.edu/la-restore/New%20Framework%20Final%20Draft.pdf.