1New Orleans, Louisiana (USA) is inextricably linked to the mighty Mississippi River that literally built the land upon which the city stands and which provided its strategic position as an entrepôt for French colonial ventures in the 18th century. With a vast hinterland, since 1718 New Orleans has served as the gateway for traditional exports consisting of furs, timber, cotton, sugar, grains, and more recently petrochemical products. A multitude of manufactured goods wind their way up river on this massive inland river system as well.
2In addition to serving as a vital route for commerce, the river drains 1.2 million square miles of North America and at peak flood stage can carry around 2 million cubic feet of water (figure1). Before the arrival of European colonists, indigenous settlers occupied high ground to avoid annual inundations while gathering food and other resources from productive floodplain wetlands. The French, seeking the most strategic site for building a colonial capital, decided to erect a city on land that was a mere 15 feet above sea level. This location provided a portage between the city and Lake Pontchartrain, a brackish lake with a natural connection to the Gulf of Mexico. They could sail ocean-going ships into the lake and portage goods a short distance into the city and avoid the difficult 100-mile passage upstream against the river’s powerful current. In addition, it was close enough to the river mouth to deter British or Spanish incursions. While it satisfied strategic concerns, it placed the city in a flood-prone location. For the last 300 years, municipal leaders have had to grapple with the risk of inundation while seeking to strike a balance with a challenging environment that would enable an urban population to survive on an ill-suited location.
Figure 1. New Orleans’s location on the lower Mississippi River.
Cartography by Clifford Dupelchin.
3This chapter will examine the use of levees to offset the risk of flooding and how that fixed infrastructure has contributed to population dynamics in the lower river valley. Early efforts to fend off floods focused on the threat of the river, and colonial and later federal efforts led to the erection of massive earthen embankments. By the 20th century, the threat of hurricane driven storm surge prompted investments in additional levees designed to complement the river barriers and keep the sea out of the city. Levee building and also failures of the levees during storms has contributed to a shifting population – a reshaping of the urban footprint. In many respects, the demographic dynamics of New Orleans are a harbinger of what we might expect to see in coastal regions around the globe facing climate-driven sea-level rise.
4A hurricane nearly destroyed the incipient city in 1722, but river floods became the most frequent threat to French settlers. By 1727, the city had erected modest levees and an 1728 colonial law mandated that rural planters construct their own levees to help create a continuous line of protection – that offered safety to rural planters and their enslaved workers and the city dwellers alike. By 1763, levees protected, albeit imperfectly, over 50 miles of riverfront above and below New Orleans. Levees encouraged additional settlement along the river. By the time of its first census as part of the U.S. in 1810, New Orleans had a population of over 17,000 people, and the bulk of the population in what became the state of Louisiana lived on plantations behind levees as well (figure 2). The commitment to levees dominated the local strategy for dealing with the nearly annual floods.
Figure 2. Levees along the river by 1812
Cartography by Clifford Dupelchin.
5The dual ironies of levees is that they encourage development in areas of risk – the so-called “levee effect.” This is exactly what happened in New Orleans. Also, on the lower Mississippi they constrict the floodplain and thereby raise the height of flood waters. Before levees, water spread out across the alluvial floodplain that was 50 to 100 miles wide and only rose to modest heights. Once confined between levees set only a few miles apart, the flood stage rose considerably. Over time but unknown in 1800, the river bed tends to rise, further aggravating the flood risk and putting greater pressure on the inconsistently made levees. To cope with both all-to-frequent levee failures during the spring floods and also the rising flood stages, local authorities continually worked to build the levees higher and higher. This demanded more and more money and prompted appeals for deferring the costs to successively higher levels of government.
6The efforts of local levee builders were far from satisfactory. One of the worst inundations occurred in 1849, when a levee built by a planter several miles upstream from New Orleans failed (figure 3). Water flowed across the agricultural land and poured into the city. It rose to depths of six feet in some of the city’s lowest neighborhoods. The high water remained in the city for several months and forced some 12,000 people to flee their homes while many businesses temporarily ceased operations. Deliberations after the flood centered on building bigger and better levees, not relocation. The city invested in strengthening its levees and population continued to grow – the levee effect in its purest form. In 1860, New Orleans was one of the ten largest cities in the U.S. with a population of 168,000. By the 1870s, the urban resident were situated safely behind a levee system that did not allow a major inundation in the city again. New Orleans’s population continued to grow to 287,000 by 1900.
Figure 3. A crevasse in the Mississippi River Levee
Courtesy New Orleans Public Library.
7Flood protection was far from complete and massive inundations of rural agricultural lands in the 1870s finally convinced the U.S. Congress to assign levee building responsibilities to a newly formed federal organization – the Mississippi River Commission. When the federal government assumed these duties and costs, it adopted a “levees-only” policy – that is, it strove to build a solid wall along the river and closed off several distributaries, or natural outlets that served as safety valves for floodwaters. It cost far less to armor only the main river channel and not the several distributaries. This policy and its infrastructure perpetuated, and even aggravated, the perpetual problem of rising flood stages.
8Major floods in the early 20th century drove additional investments in ever taller levees. When the disastrous flood of 1927 inundated 20,000 square miles of land, forced some 600,000 rural residents to evacuate their homes, killed several hundred people, devastated agriculture across a wide territory, and caused damages estimated in excess of $36 million, it did not inundate New Orleans. The oldest and strongest levees in the entire system protected the major city on the lower river. Although the city survived unscathed, revisions to the flood control policy after 1927 placed an enormous emphasis on protecting this key urban center. Engineers proposed a revamped approach which they referred to as “levees and outlets.” They foresaw the construction of a pair of artificial outlets, structures that would divert controlled flow of flood water to the Gulf of Mexico and thereby reduce pressure on the levees at New Orleans. The first outlet was positioned just upstream from New Orleans and to redirect water to Lake Pontchartrain where it would flow into the gulf. Its primary purpose was to protect the city and an emerging petrochemical industry, and secondarily it protected sugar plantations. A larger diversion was designed to divert excess flow down the Atchafalaya River, a major distributary. All in all, these multi-million dollar projects have protected the city, even during major floods in 1973 and again in 2011.
9In addition to the outlets, the high waters of 1927 forced a recalculation of risk throughout the valley, and inspired another phase of levee enlargement. For every foot a levee is raised, it requires many feet of horizontal space to support the higher elevation. So the new levee system displaced people from the diversion channels and from the areas needed to accommodate the wider footprint of the levees. Hundreds of families had to sell their homes and relocate - a type of forced environmental migration. Businesses, churches, and even cemeteries were displaced in the process. Officials claimed there was little opposition because residents desired enhanced protection. Ultimately, the huge investments in levees and outlets represented a commitment to a largely fixed structural infrastructure that encouraged continued development in the high-risk floodplain.
10With constant improvement to the levee system in the 20th century, the principal city in the lower valley continued to grow and major petrochemical complexes found the floodplain a viable and adequately secure location. New Orleans’s population reached nearly half a million by 1930. Accompanying urban growth, major oil companies began buying riverfront land and erecting refineries. Initially they clustered near Baton Rouge, well above any flood risk, and upstream and downstream from New Orleans (figure 4). Riverside sites offered ready access to ocean-going shipping, plus water for processing and waste removal. Safety principles at the time encouraged manufacturers to include a buffer zone around their new plants to minimize risk to neighbors. Plants built near New Orleans and Baton Rouge incorporated this guidance initially. Yet, where the factories grew, populations followed, and over time the buffers suffered encroachment. Both factories and communities grew – behind the safety of the massive levees.
Figure 4. Norco Refinery a few miles upstream from New Orleans.
Courtesy Louisiana Digital Library.
11During World War II and in the following decades, the petrochemical industry expanded across the lower Mississippi River floodplain. Much of the post-war growth took place in rural areas between the two initial refining nodes. Companies could acquire sugar cane acreage for relatively low prices and in more rural areas they did not face restrictions on the emission of noxious emissions and the river handily diluted liquid wastes. By 2000, there were some 150 industrial facilities lining the river.
12These industries spurred the growth of many small communities near their operations. Good paying industrial jobs enabled former agricultural communities to prosper. Yet, the benefits did not flow equally through society. There were few jobs for the many African American who lived in the area, other than custodial positions. During this phase of industrial growth, corporate officials tended to ignore the safety guidelines and failed to include buffer zones adjacent to new facilities. It was common for companies to construct noisy, emission-releasing factories adjacent to small linear settlements on the floodplain. Numerous plantation owners, after the American Civil War, gave former slaves slivers of property where they established rural communities. When the petrochemical industry arrived, corporate decision-makers apparently gave little thought to the risks or nuisances they would create for residents in these “fencerow” communities. Over the years, community members have mounted environmental justice campaigns to secure corporate funding for buyouts and relocation of residents exposed to the hazardous conditions in the shadow of the industrial operations.
13In other instances new refineries or processing plants dislodged small, often African American communities. Petrochemical giants acquired portions of former sugar operations, particularly the sites of former grinding mills – the industrial component of plantations – and the former workers’ quarters. Other plants acquired entire communities and the residents had to move to make way for the new economic activities. In either instance, communities of African Americans found themselves displaced during the last quarter of the twentieth century.
14Levees, to a large extent, facilitated this urbanization of the floodplain. Even though the levee enlargements displaced urban and rural neighborhoods that were in the footprint of the larger structures, the number of people forced to move was only a tiny fraction of the total population. Industrial expansion, and the attendant growth of floodplain towns, was made possible by the presence of the flood-control infrastructure.
15When a devastating hurricane drove storm surge into the city’s lakefront neighborhoods in 1915 and severely damaged as many as 25,000 homes. Local officials sought to eliminate future damages, and they turned to a familiar technology, levees, to protect the growing city. Over the next two decades, the local levee board gradually erected a 9.5 foot high seawall along the lakefront on the north side of the city – the area most susceptible to hurricane storm surge. This structure enabled the expansion of residential neighborhoods into the areas inundated in 1915.
16Another major storm drove storm surge into the city and the neighboring parish in 1947. Although the number of homes damaged was considerably less than in 1915, local officials again sought to erect additional levees in areas that were inadequately protected – extending the fortifications to protect emerging suburban neighborhoods that were part of the post-war suburban sprawl. By the mid-1950s, levees protected a long expanse of the city’s lakefront. Yet, this barrier was not up to the task of preventing flooding caused by Hurricane Betsy in 1965. This storm drove water into section of the city not yet protected by levees. It caused major damage to some 15,000 homes and inundated a sizable territory known as east New Orleans. The three storms of the 20th century demonstrated the weakness of hurricane levees. Unlike rivers, hurricanes follow different paths, the move at variable speeds, and have varying wind speeds and storms surges. Thus, it is common for levees built to protect against the last storm to be ineffective for the next.
17After the 1965 storm, not surprisingly, local leaders called on the federal government to expand the flood protection fortifications. Congress swiftly approved a major hurricane protection system that would enlarge the barriers for areas already armored and expand them to include the eastern sections of the city that were less secure and had suffered the most recent damage. The levee construction moved forward slowly, but the city and adjacent parishes encouraged development within the intended protection system. During the next half decade, municipal authorities approved dozens of new subdivisions within the very footprint of the area flooded in 1965. Populations swelled in the low-lying, surge-susceptible neighboring parishes of St. Bernard and Jefferson – well before the levee system was completed.
18Some have called the movement to the suburban parishes a type of environmental migration – moving from New Orleans where there was flooding to areas where there was not flooding. However, this description overlooks both the precise areas of development and the larger social trends of the 1960s and 1970s. There was extensive development in the new suburbs in eastern New Orleans directly in areas that had been flooded (figure 5). And the same was true for St. Bernard Parish. So movement was not to flee from areas of flood risk. The principal impetus was the national patterns of suburban sprawl and white flight. White residents sought to leave an increasingly African America city center, and in New Orleans, integration of schools was a prime factor in this racially influenced process. Furthermore, interstate highways provided means to commute to city-center jobs, and suburban developments offered more house for less money than inner city real estate. The levee-effect also played a role by providing a sense of security for the new suburban residents.
Figure 5. Residential subdivisions approved by the city after Hurricane Betsy
Note the concentration in areas flooded in 1965.
Cartography by Clifford Duplechin
19When Hurricane Katrina overwhelmed the incomplete levee system in 2005, it exposed serious flaws in the structures and caused extensive damage and shocking loss of life. About 80 percent of the city was inundated after a series of levee failures, over 1,000 people lost their lives, and more than 100,000 homes suffered major damage (figure 6). Despite massive investment in structural protection, a storm with lower wind speeds in the city than Betsy in 1965 caused far more destruction.
Figure 6. Flooding in New Orleans due to Hurricane Katrina 2005.
Cartography by Clifford Dupelchin.
20In the wake of Katrina, we have seen what could be called environmental migration. New Orleans proper has lost about 20 percent of its pre-storm population – nine years after the storm. Adjacent St. Bernard Parish, which also suffered major flooding has seen about half its residents relocate. Within the city, areas with the most extensive flood damage have experienced the most dramatic population losses. There has been a corresponding surge in population growth in upstream parishes and also in parishes north of Lake Pontchartrain – areas that did not see extensive flooding in 2005. This has transformed New Orleans from a compact city to one that effectively circles Lake Pontchartrain and extends up river through several parishes.
21From its founding, New Orleans has been the primary driving force for levee protection in the lower Mississippi River. Colonial laws and later federal policies after the 1927 flood directed the construction of levees and related infrastructure to fend off high water for the major city of the region. Urban growth justified the expenditures to reduce risk to business, citizens, and industry. The long line of levees also offered protection for agriculture and the petrochemical industry and encouraged intensive development across the floodplain. Since the 1860s, the levees largely protected the city.
22With the presumed control of the river, hurricane driven flooding became the most prominent risk in the 20th century. A series of hurricanes that caused extensive damage prompted calls for barriers along the city’s lakefront and eastern suburbs. Each storm followed a different path and damaged different areas. Levee building sought remedial protection and gave citizens a false sense of security. The metropolitan area continued to grow, although New Orleans proper lost population to its suburbs after 1965. The massive levee failures in 2005 destroyed that sense of security. Hurricane Katrina exposed weaknesses in the levees and prompted a major out-migration. New Orleans has lost a considerable number of citizens since this storm, but the urban area now occupies a much larger territory. Despite the repeated failures of structural protection in the past, the principal protection strategy remains levees, augmented by evacuation. With the ever expanding urban population, the territories where people demand levees also grows. This process increases the costs of levee construction and maintenance which places even greater demands on government bodies facing fiscal constraints.
23The movement of population around New Orleans, in spurts after major calamities, suggests a pattern that has relevance for climate-driven sea level rise globally. Rather than complete abandonment of major coastal cities, retreat to less risky locations, by those with the means to migrate should be anticipated. Investments in fixed infrastructure does little do assist with mitigating future hazard impacts and indeed delays a more orderly and socially supported resettlement.
24Acknowledgments: Research funding came from the U.S. Army Corps of Engineers, the Community and Regional Resilience Institute. Research assistance was provided by Peter Kamau, Amy Sumpter, Alexandra Giancarlo, and Jenny Hay.