Once again, I want to tell the story of Hurricane Katrina. Not the political one, but the ecological and engineering story. The story about the wetlands, and the levees that destroyed them. In the aftermath of Hurricane Katrina, this story needs to be told more than any other. It explains the magnitude of the Katrina tragedy, which was not only the a result of human and political mistakes that you may have heard of, but of long term errors you may not have.
The tale begins thousands of years ago, long before humans inhabited the Mississippi delta. Almost all of southeastern Louisiana was built up out of the ocean by the Mississippi River. The Mississippi, which drains runoff from 31 states and 2 Canadian provinces, carries billions of tons of silt annually to its mouth. Over the last 100,000 years, up until as recently as the early twentieth century, the river annually overflowed its banks, flooding thousands of square miles of wetlands and depositing the billions of tons of silt in the process. This annual flooding gradually built up a landmass that comprises most of the southeastern Louisiana, including the Isle of Orleans.
In 1719 the French explorer Jean-Baptiste Le Moyne de Bienville founded New Orleans. Realizing the need for a port city along this magnificent river, Bienville weighed many alternatives, and finally chose the current site for economic reasons. France needed a port near the mouth of the river, one close enough to the ocean to provide easy access for very large vessels, but far enough inland that city buildings would be well-insulated from storms and on high enough ground to resist flooding. The oldest part of New Orleans, where the French Quarter now stands, fulfilled these requirements. The land he chose was (and still is) above sea level, and thus resistant to annual flooding. It stood on relatively firm ground on the natural levee built up by centuries of river deposits, and was within a day’s sail of the Gulf of Mexico, making it a better port option than points further inland and on even higher ground, such as Baton Rouge.
Unfortunately, although the oldest part of the city was built on relatively well-chosen ground, as New Orleans grew it gradually overflowed its old footprint. New suburbs developed, houses sprung up in areas further from the riverbanks, and on softer, lower ground. The larger the city got, the more people moved to flood-susceptible areas.
The story of New Orleans’s growth in the nineteeth century is a fascinating one that I cannot go into completely here, but it can be summarized by saying that in the early days the city grew along the river banks on the high ground of the natural levee until the space ran out. Then growth followed several elevated ridges, including the Esplanade and Metairie ridges. After larger levees and more sophisticated drainage canals were constructed, people began moving into the lower areas. It is worth noting that after Katrina, none of these early high ground areas, including the ridges, flooded. The early settlers knew what they were doing. It was the modern builders who forgot.
In the later 19th century, the U.S. government recognized that a problem had developed. New Orleans had become one of America’s largest shipping centers, an absolute necessity for the continued growth of trade in the Ohio and Missouri river valleys, and yet large parts of it were exposed to flooding. More importantly, the annual spring floods that built up the land in the first place presented a practical problem. It was very difficult to negotiate an overflowing river, and commerce would often shut down when the river was at flood stage. To prevent this from happening, Congress authorized a plan to raise levees along the entire southern length of the Mississippi. This allowed for year-round deep shipping channels and kept the river commerce-friendly. (This story is extremely well told in John Barry’s book The Rising Tide.)
In 1927 the Mississippi had a record flood. It was the largest natural disaster in Southern history prior to Katina; the levee broke in 127 places and flooded 27,000 square miles, killing 246 people. The 1927 Flood is a remarkable story in itself, but its relevance to Katrina is this: After the flood, Congress decided it would increase the levee strength to guarantee that such a catastrophe would never happen again. The money was approved, and the Army Corps of Engineers executed the plan.
The plan was successful. Since 1927, the Mississippi has never again overflowed its banks along its entire length from Memphis to the Mississippi Sound. Unwittingly, though, in solving an old problem the government planners had created a new one. Since the Mississippi no longer flooded, the annual silt deposits that originally built up the land in the southern delta suddenly ceased. This interruption of an ancient and beneficial natural process would in time lead to disastrous environmental damage, and make New Orleans far more vulnerable to hurricanes.
The first sign of the harm that the end of the floods might cause was subsidence. Homes and developed land throughout southern Louisiana began to sink, as the soft alluvial soil settled and compacted. With the levees in place, and without continual silt deposits to keep the land healthy and growing, the swamps dried up.
As the swamps dried up, a much more serious problem developed — land loss. Without fresh river water to nourish it, the swampland was slowly eaten away by a process known as salt water intrusion. The Louisiana marshland is very close to the ocean, and only slightly above sea level. The constant flow of fresh water from rain and flooding creates a pattern of runoff from the land outward to the ocean that not only sustains the swamp, but also prevents the salty ocean tide from working its way in. Without this regular outflow and with the land slowly sinking, the ocean saltwater crept in, killing the trees, grasses, and wildlife. St. Bernard Parish, where I made my home prior to Hurricane Katina, has large expanses of old growth cypress forests that are now dead, a direct result of the incoming Gulf water. The process of saltwater intrusion is devastating to the wetlands. Eventually all the plant life is killed, and the soft soil crumbles away in the daily tides.
New Orleans is surrounded by wetlands, a civilized oasis on the edge of one of the largest expanses of swampland in the United States. Fully 40% of the land officially classified as wetlands in the continental 48 states is in Louisiana. As the march of saltwater intrusion continues, almost all of it could be gone within a generation. In all likelihood, the process of land loss began as the construction of the current Mississippi river levee system began in the 1870s and accelerated when the project was completed in the 1930s, but scientists did not begin to fully appreciate the damage being done until 1960s. By the 1980s it was clear that land was disappearing at an alarming rate, and that the process seems to be accelerating. It is estimated the Louisiana has already lost 1900 square miles of wetlands, an area larger than the state of Delaware. Another 500 square miles will be lost by 2050. Currently, the state is losing 24 square miles a year, or the equivalent of 2 football fields every fifteen minutes.
Like most readers, when I first heard these numbers I thought there must be a mistake. Land doesn’t disappear that quickly. But I have seen this land erosion with my own eyes, and the proof is in numerous satellite photographs taken over the last thirty years. See for yourself.
The levee system, unfortunately, is not the only thing that is contributing to this shocking land loss. There is one more complicating factor. Louisiana sits on the edge of one of America’s largest oil reserves, an offshore reservoir currently estimated at over 70 billion barrels. This does not include a brand new discovery in deep water near the Lousiana-Texas border, which could increase that estimate substantially.
The size of this huge oil reserve is reflected in the number of active oil platforms off the Louisiana coast. Numbering over 4,000, these platforms make up the largest concentration of offshore drilling platforms in all of the United States, including Alaska. In the early days of oil exploration, oil wells were scattered throughout the Louisiana wetlands and in the shallow waters a short distance from the shore, in shallow water. As technology has improved, platforms have moved into deeper and deeper water.
To supply this huge number of platforms, oil companies dredged canals through wetlands. These canals were heavily used in the early days, but as of late, as platforms have moved further off the coast, many of them have been abandoned.
These access canals have also been a source of substantial coastal erosion. Daily tides and hurricane surges have repeatedly forced ocean water up these canals, hastening the process of saltwater intrusion. With each tide, and each storm, the saltwater from the ocean kills trees and grass that hold the land together, and as the plant life dies, the land crumbles and washes away. I could give you statistics and scientific opinions, but you can see it for yourself by looking at maps of the Louisiana coast. All of the straight lines that cut across the land are manmade. They are destroying the land at a rapid rate, and very little has been done to stop this process.
There was a time, even in Louisiana, when wetlands loss was not considered an important issue. Wetland, after all, is just another word for swamp, and what good is a swamp? You can’t live in a swamp (unless you are a Cajun). Swamps are desolate and useless, except when drained and put to good use. So if we lose some of it, or all of it, who cares?
That should be, given today’s state of environmental awareness, an easy question to answer. Louisiana’s wetlands are home to thousands of species of birds, including many endangered ones. There are more alligators in Louisiana than in Florida. The Louisiana wetlands produce the largest seafood catch in America, excepting Alaska, which is many times its size. And the Louisiana wetlands are the home of the Cajun people, a population of about 500,000 French speakers who comprise one of America’s most interesting ethnic groups. All of these things could be gone in our lifetimes.
The wetlands also serve a very important practical purpose here in Southeast Louisiana. They protect inland areas from hurricanes. Studies at Louisiana State University suggest that each square mile of wetlands could absorb as much as 1 foot of a hurricane storm surge. Katrina’s storm surge was about 28 feet in Louisiana. It is not hard to imagine that a landmass the size of Delaware could have absorbed much of this surge, saving many lives and billions in property damages, perhaps leaving New Orleans intact.
The process of land destruction in Louisiana started in the late 1800s when the first levee was erected along the Mississippi and has continued unabated since. Without annual flooding, the wetlands are unable to recover from the horrific damage a hurricane can deliver to the coastline. According to the US Geological survey, Katrina swept away 30 square miles of marshland in St. Bernard Parish alone, or roughly 5% of the landmass, in a single day. Before the levee system, that loss could have been rebuilt over many decades of natural flooding. After the levees, the loss is permanent.
This staggering loss of American soil goes on without any public comment on the national level. As more than one Louisianan has remarked, if a foreign nation were to invade the U.S. and occupy the state of Delaware, we would be outraged. But because the same land mass is washing away an inch at a time, no one gives a damn. We like to see dramatic stories in America. We respond with outrage when buildings blow up and bodies float in the street. But long term, gradual tragedies are not worthy of our attention, even though the net result may be far worse.
It is true that when the levee system that finally corralled the Mississippi was constructed, the builders had no idea that their work would result in wholesale destruction of public lands. In that sense, it is not fair to hold them morally responsible for the damage done. On the other hand, the destruction of the wetlands was well underway by the 1960s and well understood by Louisiana ecologists in the late 1970s. In his book Bayou Farewell, Mike Tidwell says that many researchers were aware of the damage by the early 1970s. In his book The Storm, LSU researcher Ivor Van Heerden says that he was actively publishing research on the subject by 1980.
In 1719, when New Orleans was founded, it was low-lying as it is now, but the thousands of square miles of surrounding wetlands made it far less vulnerable to hurricanes than it is now. This change in vulnerability was human doing, or to be more specific, the doing of the federal government through its efforts to maintain year-round navigability of the Mississippi river. As soon as the levee system was completed, the wetlands were doomed, and Katrina was no longer a mere possibility. It was inevitable. Inevitable that after enough land dissolved into the Gulf of Mexico, New Orleans would become so exposed that a hurricane would destroy it.
Insofar as the levee system was designed and built by the federal government, and insofar as the government ignored repeated warnings by scientists studying the wetlands that Katrina could happen, it is the responsibility of the government to at least make a good faith effort to correct the harm it has done.
The most unfortunate part of this story is that all of this was preventable. The lucky part is that, even at this late date, the coastal erosion is reversible. If the right individuals at the state and federal level recognize what is happening and choose to do something about it, much of the wetlands of Louisiana can be reconstructed. With the proper approach, the city of New Orleans could be protected from a category 5 hurricane, and the wetlands could be brought back.
In the second part of this series, I will explain how the wetlands can be saved.