Climate change and the Louisiana delta

8 09 2014

 

In the August 28, 2014 issue of Huff Post Green, an article by Bob Marshall of The Lens caught me eye, because it’s another instance of climate change affecting the landscape in one of our most vulnerable areas: the Louisiana delta. I’ve excerpted some of it; if you want to read the full article, click here. So NEXT post will be about how the textile industry is contributing to climate change!

Al Shaw of ProPublica and Brian Jacobs of Knight-Mozilla Open News

Al Shaw of ProPublica and Brian Jacobs of Knight-Mozilla Open News

In just 80 years, some 2,000 square miles of Louisiana’s coastal landscape have turned to open water, wiping places off maps, bringing the Gulf of Mexico to the back door of New Orleans and posing a lethal threat to an energy and shipping corridor vital to the nation’s economy.

And it’s going to get worse, even quicker.

Scientists now say one of the greatest environmental and economic disasters in the nation’s history is rushing toward a catastrophic conclusion over the next 50 years, so far unabated and largely unnoticed.

At the current rates that the sea is rising and land is sinking, National Oceanic and Atmospheric Administration scientists say by 2100 the Gulf of Mexico could rise as much as 4.3 feet across this landscape, which has an average elevation of about 3 feet. If that happens, everything outside the protective levees — most of Southeast Louisiana — would be underwater.

 The effects would be felt far beyond bayou country. The region best known for its self-proclaimed motto “laissez les bons temps rouler” — let the good times roll — is one of the nation’s economic linchpins.

 This land being swallowed by the Gulf is home to half of the country’s oil refineries, a matrix of pipelines that serve 90 percent of the nation’s offshore energy production and 30 percent of its total oil and gas supply, a port vital to 31 states, and 2 million people who would need to find other places to live.

 The landscape on which all that is built is washing away at a rate of a football field every hour, 16 square miles per year.

For years, most residents didn’t notice because they live inside the levees and seldom travel into the wetlands. But even those who work or play in the marshes were misled for decades by the gradual changes in the landscape. A point of land eroding here, a bayou widening there, a spoil levee sinking a foot over 10 years. In an ecosystem covering thousands of square miles, those losses seemed insignificant. There always seemed to be so much left.

Now locals are trying to deal with the shock of losing places they had known all their lives — fishing camps, cypress swamps, beachfronts, even cattle pastures and backyards — with more disappearing every day.

The story of how that happened is a tale of levees, oil wells and canals leading to destruction on a scale almost too big to comprehend — and perhaps too late to rebuild. It includes chapters on ignorance, unintended consequences and disregard for scientific warnings. It’s a story that is still unfolding.

By the time New Orleans was founded in 1718, the main channel of the river was the beating heart of a system pumping sediment and nutrients through a vast circulatory network that stretched from present-day Baton Rouge south to Grand Isle, west to Texas and east to Mississippi. As late as 1900, new land was pushing out into the Gulf of Mexico.

A scant 70 years later, that huge, vibrant wetlands ecosystem would be at death’s door. The exquisite natural plumbing that made it all possible had been dismantled, piece by piece, to protect coastal communities and extract oil and gas.

 For communities along its banks, the Mississippi River has always been an indispensable asset and their gravest threat. The river connected their economies to the rest of the world, but its spring floods periodically breached locally built levees, quickly washing away years of profits and scores of lives. Some towns were so dependent on the river, they simply got used to rebuilding.

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That all changed with the Great Flood of 1927.

Swollen by months of record rainfall across the watershed, the Mississippi broke through levees in 145 places, flooding the midsection of the country from Illinois to New Orleans. Some 27,000 square miles went under as much as 30 feet of water, destroying 130,000 homes, leaving 600,000 people homeless and killing 500.

Stunned by what was then the worst natural disaster in U.S. history, Congress passed the Flood Control Act of 1928, which ordered the U.S. Army Corps of Engineers to prevent such a flood from ever happening again. By the mid-1930s, the corps had done its job, putting the river in a straitjacket of levees.

But the project that made the river safe for the communities along the river would eventually squeeze the life out of the delta. The mud walls along the river sealed it off from the landscape sustained by its sediment. Without it, the sinking of land that only occurred during dry cycles would start, and never stop.

If that were all we had done to the delta, scientists have said, the wetlands that existed in the 1930s could largely be intact today. The natural pace of sinking — scientists call it subsidence — would have been mere millimeters per year.

But we didn’t stop there. Just as those levees were built, a nascent oil and gas industry discovered plentiful reserves below the delta’s marshes, swamps and ridges.

At the time, wetlands were widely considered worthless — places that produced only mosquitoes, snakes and alligators. The marsh was a wilderness where few people could live, or even wanted to.

There were no laws protecting wetlands. Besides, more than 80 percent of this land was in the hands of private landowners who were happy to earn a fortune from worthless property.

Free to choose the cheapest, most direct way to reach drilling sites, oil companies dredged canals off natural waterways to transport rigs and work crews. The canals averaged 13 to 16 feet deep and 140 to 150 feet wide — far larger than natural, twisting waterways.

 Eventually, some 50,000 wells were permitted in the coastal zone. The state estimates that roughly 10,000 miles of canals were dredged to service them, although that only accounts for those covered by permitting systems. The state began to require some permits in the 1950s, but rigorous accounting didn’t begin until the Clean Water Act brought federal agencies into play in 1972.

“Once the oil companies come in and started dredging all the canals, everything just started falling apart,” said Joseph Bourgeois, 84, who grew up and still lives in the area.

From 1930 to 1990, as much as 16 percent of the wetlands was turned to open water as those canals were dredged. But as the U.S. Department of the Interior and many others have reported, the indirect damages far exceeded that:

  • Saltwater creeped in

Canal systems leading to the Gulf allowed saltwater into the heart of freshwater marshes and swamps, killing plants and trees whose roots held the soils together. As a side effect, the annual supply of plant detritus — one way a delta disconnected from its river can maintain its elevation — was seriously reduced.

  • Shorelines crumbled

Without fresh sediment and dead plants, shorelines began to collapse, increasing the size of existing water bodies. Wind gained strength over ever-larger sections of open water, adding to land loss. Fishers and other boaters used canals as shortcuts across the wetlands; their wakes also sped shoreline erosion. In some areas, canals grew twice as wide within five years.

  • Spoil levees buried and trapped wetlands

When companies dredged canals, they dumped the soil they removed alongside, creating “spoil levees” that could rise higher than 10 feet and twice as wide.

The weight of the spoil on the soft, moist delta caused the adjacent marshes to sink. In locations of intense dredging, spoil levees impounded acres of wetlands. The levees also impeded the flow of water — and sediments — over wetlands during storm tides.

If there were 10,000 miles of canals, there were 20,000 miles of levees. Researchers estimate that canals and levees eliminated or covered 8 million acres of wetlands.

 All this disrupted the delta’s natural hydrology — its circulatory system — and led to the drowning of vast areas. Researchers have shown that land has sunk and wetlands have disappeared the most in areas where canals were concentrated.

There are other forces at work, including a series of geologic faults in the delta and the rock layers beneath, but a U.S. Department of Interior report says oil and gas canals are ultimately responsible for 30 to 59 percent of coastal land loss. In some areas of Barataria Bay, it’s close to 90 percent.

 Even more damage was to come as the oil and gas industry shifted offshore in the late 1930s, eventually planting about 7,000 wells in the Gulf. To carry that harvest to onshore refineries, companies needed more underwater pipelines. So they dug wider, deeper waterways to accommodate the large ships that served offshore platforms.

 Congress authorized the Corps of Engineers to dredge about 550 miles of navigation channels through the wetlands. The Department of Interior has estimated that those canals, averaging 12 to 15 feet deep and 150 to 500 feet wide, resulted in the loss of an additional 369,000 acres of coastal land.

 Researchers eventually would show that the damage wasn’t due to surface activities alone. When all that oil and gas was removed from below some areas, the layers of earth far below compacted and sank. Studies have shown that coastal subsidence has been highest in some areas with the highest rates of extraction.

 The oil and gas industry, one of the state’s most powerful political forces, has acknowledged some role in the damages, but so far has defeated efforts to force companies to pay for it.

 Even as politicians fought the lawsuit, it was hard to deny what was happening on the ground.

By 2000, coastal roads that had flooded only during major hurricanes were going underwater when high tides coincided with strong southerly winds. Islands and beaches that had been landmarks for lifetimes were gone, lakes had turned into bays, and bays had eaten through their borders to join the Gulf.

Today, in some basins around New Orleans, land is sinking an inch every 30 months. At this pace, by the end of the century this land will sink almost 3 feet in an area that’s barely above sea level today.

Meanwhile, global warming is causing seas to rise worldwide. Coastal landscapes everywhere are now facing a serious threat, but none more so than Southeast Louisiana.

The federal government projects that seas along the U.S. coastline will rise 1.5 to 4.5 feet by 2100. Southeast Louisiana would see “at least” 4 to 5 feet, said NOAA scientist Tim Osborn.

 The difference: This sediment-starved delta is sinking at one of the fastest rates of any large coastal landscape on the planet at the same time the oceans are rising.

Maps used by researchers to illustrate what the state will look like in 2100 under current projections show the bottom of Louisiana’s “boot” outline largely gone, replaced by a coast running practically straight east to west, starting just south of Baton Rouge. The southeast corner of the state is represented only by two fingers of land – the areas along the Mississippi River and Bayou Lafourche that currently are protected by levees.

 Similar predictions had been made for years. But Hurricane Katrina finally galvanized the state Legislature, which pushed through a far-reaching coastal restoration plan in 2007.

 The 50-year, $50 billion Master Plan for the Coast (in 2012 dollars) includes projects to build levees, pump sediment into sinking areas, and build massive diversions on the river to reconnect it with the dying delta.

The state’s computer projections show that by 2060 — if projects are completed on schedule — more land could be built annually than is lost to the Gulf.

But there are three large caveats.

  • The state is still searching for the full $50 billion. Congress so far has been unwilling to help.
  • If the plan is to work, sea-level rise can’t be as bad as the worst-case scenario.
  • Building controlled sediment diversions on the river, a key part of the land-building strategy, has never been done before. The predictions, then, are largely hypothetical, although advocates say the concept is being proven by an uncontrolled diversion at West Bay, near the mouth of the river.

 Trying to keep pace with the vanishing pieces of southeast Louisiana today is like chasing the sunset; it’s a race that never ends.

Signs of the impending death of this delta are there to see for any visitor.

Falling tides carry patches of marsh grass that have fallen from the ever-crumbling shorelines.

Pelicans circle in confusion over nesting islands that have washed away since last spring.

Pilings that held weekend camps surrounded by thick marshes a decade ago stand in open water, hundreds of yards from the nearest land — mute testimony to a vanishing culture.

Shrimpers push their wing nets in lagoons that were land five years ago.

The bare trunks of long-dead oaks rise from the marsh, tombstones marking the drowning of high ridges that were built back when the river pumped life-giving sediment through its delta.

“If you’re a young person you think this is what it’s supposed to look like,” Lambert said. “Then when you’re old enough to know, it’s too late.”

 


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9 09 2014
sondasmcschatter

Reblogged this on sondasmcschatter and commented:
I LOVE HER BLOG POSTS—————-

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