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Authors: Brian Fagan
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kilometers of coastal barrier, the Mississippi equivalent of the Bangladeshi mangroves is drastically reduced. The vanishing marshes caused the corps to build an encircling levee around New Orleans, turning it into a fortified city—this before one figures in the sea level rises of the future.
At this point, many experts believe that the coast is beyond salvation, as entire parishes vanish and nutrient and sediment starvation wreakhavoc on the coastal landscape. Today, much Mississippi water flows down the Atchafalaya, which is the main route by which severe floodwaters reach the Gulf. Morgan City, Louisiana, has a flood stage about 1.2 meters above sea level and lies directly in the flood’s path. Huge walls 6.7 meters high surround the small town, which must be one of the most vulnerable human settlements on earth. 8 It is as if the city dwells atop an occasionally active volcano, its fate decided by flood control installations up at Old River, far upstream. This is apart from the storm surges caused by hurricanes. Weather conditions over 42 percent of the United States determine the long-term survival of Morgan City. Floods here last not weeks as they do upstream, but months, for the more people upstream protect themselves with rings of levees, the more water arrives downstream.
Figure 13.4 The dedication of A. Baldwin Wood’s pumping station in New Orleans, 1915. Author collection.
THANKS TO HUMAN activity, the Gulf Coast is sinking, sea levels are rising, and humans have effectively reversed nature. Or have they? This is hurricane country, and when such storms arrive they tear into the coast and accelerate erosion dramatically, making for an even more severe threat of destruction from the south than from the north.
Hurricanes entered recorded delta history dramatically in 1722, when one such storm led some French settlers of New Orleans to suggest that the city was uninhabitable. In 1779, another even more severe hurricane razed the city completely. A long history of devastation of barrier islands and inland villages also haunts the coast, but people have always stayed—to farm, to fish, and, in more recent times, because of oil. Rising sea levels compound the problem as they encroach on the eroding and subsiding delta shore. By the 1970s, the estimated annual loss was about a hundred square kilometers a year. The rate has slowed since then, as oil and gas activity has declined somewhat and measures were taken to reduce the loss, which now stands at somewhere between sixty-five and ninety square kilometers annually. Then there are sea surges, which created some seven hundred square kilometers of open water at the expense of wetland in the 2005 hurricane season alone.
In earlier times, before human interference, sediment maintained theelevation of the wetlands and fed the offshore barrier islands, many of which are now disappearing in the face of hurricanes and rising sea levels. Tidal gauge data for Louisiana record a sea level rise of nearly a meter over the past century, most of it caused not by global changes in ocean volume but by subsidence. If the local sea level were to rise 1.8 meters between now and 2100, all efforts to restore the wetlands would be canceled out and New Orleans would be seriously threatened. This is why Hurricane Katrina was a defining moment in the adversarial relationship between humans and the ocean.
Poverty Point may have been vulnerable to river floods, sea level shifts, and climate change, but its people could disperse into villages and resettle elsewhere. Today, millions of people live on the low-lying coastal plains of the Lower Mississippi region, where warming temperatures, rising sea levels, and a projected higher frequency of extreme weather events pose serious threats to much larger, far more vulnerable populations. When Katrina came ashore on the Gulf Coast in 2005, Americans received a harsh lesson in the frightening vulnerability of densely populated cities lurking
At this point, many experts believe that the coast is beyond salvation, as entire parishes vanish and nutrient and sediment starvation wreakhavoc on the coastal landscape. Today, much Mississippi water flows down the Atchafalaya, which is the main route by which severe floodwaters reach the Gulf. Morgan City, Louisiana, has a flood stage about 1.2 meters above sea level and lies directly in the flood’s path. Huge walls 6.7 meters high surround the small town, which must be one of the most vulnerable human settlements on earth. 8 It is as if the city dwells atop an occasionally active volcano, its fate decided by flood control installations up at Old River, far upstream. This is apart from the storm surges caused by hurricanes. Weather conditions over 42 percent of the United States determine the long-term survival of Morgan City. Floods here last not weeks as they do upstream, but months, for the more people upstream protect themselves with rings of levees, the more water arrives downstream.
Figure 13.4 The dedication of A. Baldwin Wood’s pumping station in New Orleans, 1915. Author collection.
THANKS TO HUMAN activity, the Gulf Coast is sinking, sea levels are rising, and humans have effectively reversed nature. Or have they? This is hurricane country, and when such storms arrive they tear into the coast and accelerate erosion dramatically, making for an even more severe threat of destruction from the south than from the north.
Hurricanes entered recorded delta history dramatically in 1722, when one such storm led some French settlers of New Orleans to suggest that the city was uninhabitable. In 1779, another even more severe hurricane razed the city completely. A long history of devastation of barrier islands and inland villages also haunts the coast, but people have always stayed—to farm, to fish, and, in more recent times, because of oil. Rising sea levels compound the problem as they encroach on the eroding and subsiding delta shore. By the 1970s, the estimated annual loss was about a hundred square kilometers a year. The rate has slowed since then, as oil and gas activity has declined somewhat and measures were taken to reduce the loss, which now stands at somewhere between sixty-five and ninety square kilometers annually. Then there are sea surges, which created some seven hundred square kilometers of open water at the expense of wetland in the 2005 hurricane season alone.
In earlier times, before human interference, sediment maintained theelevation of the wetlands and fed the offshore barrier islands, many of which are now disappearing in the face of hurricanes and rising sea levels. Tidal gauge data for Louisiana record a sea level rise of nearly a meter over the past century, most of it caused not by global changes in ocean volume but by subsidence. If the local sea level were to rise 1.8 meters between now and 2100, all efforts to restore the wetlands would be canceled out and New Orleans would be seriously threatened. This is why Hurricane Katrina was a defining moment in the adversarial relationship between humans and the ocean.
Poverty Point may have been vulnerable to river floods, sea level shifts, and climate change, but its people could disperse into villages and resettle elsewhere. Today, millions of people live on the low-lying coastal plains of the Lower Mississippi region, where warming temperatures, rising sea levels, and a projected higher frequency of extreme weather events pose serious threats to much larger, far more vulnerable populations. When Katrina came ashore on the Gulf Coast in 2005, Americans received a harsh lesson in the frightening vulnerability of densely populated cities lurking
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