Call for Ideas Lens: Environment

Geography of New Orleans

BY RICHARD CAMPANELLA

 
 
 

New Orleans occupies a relatively rare geomorphological phenomenon: a delta in which the quantity of river-deposited alluvium overwhelmed the erosive effects of sea currents and tides. What ensued, over seven millennia, is one of the world’s biggest, best examples of a river-dominated (fluvial) delta, prograding a hundred or so miles seaward into the Gulf of Mexico. (Most other deltas are wave- or tide-dominated, meaning that the sea “wins the battle,” sweeping away most river-deposited sediment and leaving the delta more or less flush with the coastline.) The resulting Mississippi River Deltaic Plain originally lay entirely above sea level, with its natural levees two to three meters high, paralleling the Mississippi River and its distributaries. Behind them were freshwater swamps, and lining the coastal fringe were wetlands and saline marshes. It was a dynamic and fluid environment, halfway between hydrosphere and lithosphere.

Ecological abundance and convenient access attracted humans to the delta, even as the Mississippi continued to jump channels and overtop its banks. Indigenous peoples occupied the delta provisionally, moving to higher ground when the floodwaters came. European colonials, on the other hand, sought permanent settlement, and starting in the 1700s, engineers endeavored to impose rigidity upon deltaic fluidity, in the form of artificial levees and drainage canals. 

In time, these structures would enable New Orleans to grow and prosper as a built environment, even as they disrupted vital deliveries of fresh water and sediment to the physical environment. Later, engineers drained the swamps and marshes, and developers urbanized the “reclaimed” land into valuable real estate—all with civic complicity. New Orleans thus began to spread onto lower ground and sprawl beyond its crescent of natural levees to become a modern metropolis, twenty miles across. 

But that removal of runoff and groundwater opened up cavities in the finely textured swamp soils, which, dried and oxidizing, proceeded to subside below sea level. Concurrently, over ten thousand linear miles of petroleum and navigational canals were excavated throughout the deltaic plain, allowing salt water to intrude and further erode already-deteriorating wetlands. 

Coastal Louisiana began to lose over 2000 square miles of land, while greater New Orleans sunk into a series of topographic bowls. Human activity had essentially converted a river-dominated delta into a sea-dominant system, ever more dependent on barriers to keep the rising seawater at bay. When some of those levees and floodwalls breached in the face of Hurricane Katrina’s storm surge in 2005, the deleterious effects of three centuries of deltaic tampering came to light, and proved utterly catastrophic. 

As New Orleans enters its fourth century, local architects confront the same challenges shared by their peers elsewhere, such as energy efficiency, rainwater catchment, and the use of recycled materials. But they also grapple with geographical variables distinct to this delta. As our forebears understood, the best—arguably, the only—terrain suitable for building here is the natural levees, which, not coincidentally, are also the only major urbanized areas that remain above sea level. The farther and lower we go from these relatively high ridges, the weaker grows the case for sustainable human habitation. If you design an architecturally sustainable structure in geographically unsustainable place, you’ve nullified the benefits of your design and likely increased human exposure to hazard. Yet to the extent that architecture is a client-driven profession, geographical location is the one variable usually beyond the control of the architect. So the geographical questions posed for futureNOLA architects: 

Does a designer committed to architectural sustainability have an obligation to take a stand on the geographical suitability of the client’s site, at the risk of losing the commission? 

Relatedly, who’s to say whether a particular geography is unsustainable? Is everything within the Hurricane Storm Surge Risk Reduction System “fair game”? Are local zoning codes and FEMA Flood Insurance Rate Maps good enough, and if so, to what level of risk—1 percent, 0.2 percent, or lower? 

Does elevating a structure above base flood elevation fully satisfy the architect’s responsibility to design against flooding, even though the surrounding community could still inundate? Would you accept a commission to design a sustainable home in, say, Venetian Isles? Lake Catherine? Braithwaite? Lafitte? What about the rear of the Lower Ninth Ward? 

Given the wide range of predictions of climate change impacts and sea level rises, which should become the profession’s standard? 

Or is all this asking too much of a profession fundamentally responsible for structural design, not regional planning?


FOR FURTHER READING:

Campanella, Richard, Bienville’s Dilemma: A Historical Geography of New Orleans. University of Louisiana Press, 2008.

Colten, Craig E., An Unnatural Metropolis: Wresting New Orleans from Nature. Louisiana State University Press, 2006. 

Day, John W., Matthew Moerschbaecher, David Pimentel, Charles Hall, and Alejandro Yánez-Arancibia, “Sustainability and Place: How Emerging Mega-Trends of the 21st Century Will Affect Humans and Nature at the Landscape Level.” Ecological Engineering, 2013.

Reese, Carol McMichael, Michael Sorkin, and Anthony Fontenot, editors, New Orleans Under Reconstruction: The Crisis of Planning. Verso Books, 2014.

RCampanella_please credit to Paula Burch-Celentano ofTulane  University.jpg

Richard Campanella.
Photograph by Paula Burch-Celentano of Tulane University.

Richard Campanella, a geographer with the Tulane School of Architecture, is the author of ten books and over 200 articles on the geography, history, and culture of New Orleans and related topics. He may be reached at http://richcampanella.com, rcampane@tulane.edu, and @nolacampanella.