OPPORTUNIST ADAPTATIONand Infrastructural Landscapes: Bonnet Carré Spillway

Essay by Kees Lokman and Travis BostSeptember 2011

Introduction

The impact of industrialized urbanism of the nineteenth and early twentieth century on the landscape was un-precedentedly extensive. Industrial production and com-merce were assuredly the impetuses behind this phase of urbanization however the method of conveyances for production and urbanization was the development of large-scale infrastructures to support this enormous growth. They served generally to conquer space by time and more specifically to early industrialization to conquer nature as a human enemy. Yet further, the noxious condi-tions and difficult geography of industrialization required the implementation of infrastructures to ‘solve’ problems created by industry (such as sanitation). These com-pounded infrastructures still leave significant marks on the built landscape today while, despite declarations of a post-industrial condition in the developed world, ever newer infrastructural systems are continuing to be laid. The engineered ‘solutions’ of the industrial era were largely built for a single function that addressed a particular ill to urbanization or commerce at a given time

and place. Their designs sought to improve efficiency and consistency, and reduce risk or uncertainty. Thus rails, wires, pipes, conduits, and bridges smooth the otherwise messy conditions of the natural, while levees, dams, and canals sought to externalize the natural and its coordinate risk. In order to assure risk management and consistent operation, the structures of these systems are heavy and inflexible. This incongruity is desperately pronounced as nearly all serve as conduits of flow for re-sources, energy , or commerce. Industrial era infrastruc-tural can thus be described as facilitating conveyence of flows along while eliminating flow across. However, this essay will present the possibility for openness of adaptation in function and operation of these same infrastructures and landscapes. The open-ing up of opportunities for adaptation of infrastructural landscapes (both aging and to come) will prove increas-ingly crucial in a present of post-industrial, globalized ur-banism. Presented here is research exploring the Bon-net Carré Spillway as an example of a multi-functional, multi-dimensional infrastructural landscape, which oper-ates as an open framework for emergent economic and ecological opportunities.

Mississippi River and Tributaries Project

The Great Flood of 1927 was the worst flood on the Mis-sissippi in the history of the United States, inundating 26,000 square miles and displacing 600,000 people.[1] The resulting congressional Flood Control Act of 1928 authorized the Mississippi River and Tributaries Project (MR&T).[2] This was the first totalizing system of flood control on the river, rather fragmented levee boards. The paramount goal of the project was to protect the Lower Mississippi Valley, home to 4.5 million people, from a hy-pothetical flood, far worse than that of 1927. [3] The MR&T proposed a shift from the previously accepted strategy for flood control that called for ever-higher levee construction since the first levees of 1717. [4] The designed system of operation, called for four floodways that would each be opened separately in re-sponse to specific flow rates and river gauges in particu-lar parts of the river to lower the flood stage in the main channel. Artificial crevasses, distributaries, and spillways had been proposed in the past, including Carroll Riker’s fantastical ‘overland seaway’, but were dismissed largely due to the strong faith in levees.[5] In contrast to the Figure 1: MR & T Project Design - US Army Corps of Engineers

larger, seldom opened floodways at Birds Point-New Ma-drid, Morganza, and West Atchafalaya that are opened by dynamiting dedicated levees, the Bonnet Carré Spill-way is an operable mechanical structure, opened nine times in its history, most recently in 2008.[6]

Spillway Operations

The 7,623 acre Bonnet Carré Spillway was rapidly com-pleted in 1932 with a number of technical advances in-cluding unprecedentedly deep timber pilings and strong concrete, both far beyond the norm for the period, ac-cording to the Army Corps of Engineers website Novem-ber 2010. The design features a smaller than standard levee – approximately eleven feet in height – along the riverbank that is higher than normal river stage for the majority of the year. The structure itself is located approx-imately 800 feet back from the river. It is an enormous concrete weir, 7,000 feet in length divided into 350 bays; the bays each contain a fence of twenty 12” x 12” creo-

sote timbers standing on end, blocking the water’s flow into the spillway land behind. In times of exceptionally high water, twin diesel-powered cranes, riding on parallel tracks atop the concrete bays, pull the timbers to release the water. Directed by the upper and lower guide levees, the water then runs across the nearly six mile length of the spillway lands at up to 250,000 cubic feet per sec-ond and into the shallow, brackish Lake Pontchartrain, eventually draining to the Gulf of Mexico. This process generally lasts from one to two months and leaves ap-proximately nine million cubic yards of sediment. Addi-tionally, during the Spring months when water levels are highest, the weir leaks considerably – up to 10,000 cfs – adding beneficial freshwater, nutrients, and sediments to the spillway and lake ecosystems.

Emergent Economies

As the spillway was planned, it had to negotiate the pre-existing infrastructures of the roadways and railway lines.

Figure 2: Bonnet Carre Spillway as part of a larger network of spillway systems along the MIssissippi River.

These uses were the only economies on or traversing the site at the time (other than the demolished plantation); however the spillway lands have since transformed to fa-cilitate many hard infrastructural economies both trans-situ and in-situ. These infrastructures were initially seen as simply coincident, not in line with the single-purpose engineering.[7] The three rail lines, US-61, and later Interstate-10 were therefore externalized from the spillways lands by raising them on piles or trestles to a separate plane of infrastructural activity, hydrological below and economic

above. River Road, along the levee’s crest, was the exception. It was integrated into the system by being moved behind the structure to be flooded during open-ings. The roadway therefore becomes a flexible convey-ance right-of-way – sometimes transferring traffic along its length, other times water is conveyed laterally across its width. New Orleans’ only land bridge to the continent thus becomes a flexible causeway.

Regional and national power grids and later the petroleum industry developed in the area, each cutting extensive networks throughout of the delta’s marshes to house cables, transmission lines, and pipelines. These infrastructures were more readily given right-of-way and today network across the spillway lands. From minimally accommodating existing industry to allowing new indus-try to affect the grounds, the Army Corps of Engineers went further to allow the drilling of twenty oil and gas wells on the grounds. Where once commerce travelled above, then through and below the spillway, now it would also flow in and out of the area as well. Operated by the large locally-based oil industry, profit went to both private and federal interests. The mentality therefore softened from single-purpose, hard engineering to one of layered uses and economies. But these economies need not be necessarily independent and sedimentary but could also be symbi-otic. After the first openings of the spillway, an informal economy developed, unanticipated by the original de-sign, mining and selling the vast silt deposits left within the spillway. This economy is net positive for not only the excavation companies which are currently given open rights to the soil, but also for the Army Corps as this ma-terial must necessarily be cleared in order for the struc-ture to function properly. The current 10-year average frequency of opening interfaces with the excavation ca-

Figure 3: section through length of Bonnet Carré Spillway, Mississippi River, left, flows to Lake Pontchartrain, right.

Figure 4: section through weir structure of Bonnet Carré Spillway.

Figure 5: lateral section of spillway, water flows through area channelled by left and right guide levees with infrastructure aobve and below.

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pacity of the operation which takes several years to haul the deposits from a single spillway opening. The Army Corps has now begun a strategy to both standardize and profit from this business by initiating a competitive bid process for excavation rights. Waste has been acknowl-edged as resource. This sand is used not only as fill for construction projects in the nearby cities but is also used as fill by property owners to raise their subsiding land. After the 2005 hurricane season, clay also began to be excavated from the site to be used in reinforcement of the area’s storm surge levees. This economy there-fore mimics the natural process of sedimentation by the river that would replace subsiding soil and build natural levees by seasonal flooding. Economy and ecology be-come conflated. This fluid interplay is a soft adaptation and extension of the initially designed engineering.

Soft Systems

While secondary infrastructures and economies are be-

ing legitimated in the Bonnet Carré Spillway, other un-planned soft adaptations have developed for human ac-tivity outside of the original design. Without a formalized plan for recreation in the enormous area, residents have appropriated the space for boating, hunting, fishing, fire-arm shooting, hiking, camping, model airplane flying, as well as ATV and 4x4 vehicle use. Some of these uses have been accommodated semi-formally through out-grants though many continue with the casual approval of the spillway’s operating staff. The recent master plan studies show the Corps has aimed at legitimizing as many of the current legal uses as possible. Planning of current and future use occurs in re-lationship to the other functions within the spillway. With the periodic flooding come silt deposits; these are exca-vated, leaving borrow pits which are then occupied by local wildlife as well as stocked with game fish for fishing, hunting and birding. The haul roads built by the excava-tion companies are maintained by the spillway staff and used by recreational visitors to access the interior areas. ATV, 4x4, dirt bikers, and mountain bikers make use of

Figure 6: material flows from the Bonnet Carré Spillway.

the uneven terrain and borrow pits of the excavation operation as trails and obstacles. All of these activities are subservient to the central function of the structure and therefore shift in location or change in function or character in response to the decennial flooding and the biannual heavy leaking through the structure from high tides. Moreover, the opening of the spillway has become a massive spectacle, advertised in advance by local me-dia, drawing thousands to watch the slow process. En-gineering becomes theatre. The shifting ecology of the river governs the soft, networked ecology of the opera-tional and recreational uses of an originally single-use structure. In its latest master plan, the National Econom-ic Development Index is used to estimate a monetary value for the recreational functions of the spillway at 3.5 million dollars annually. By associating a dollar amount, the auxiliary and soft become integral extensions of en-gineering that complement the functioning of the whole design.

Environmental Dynamics

When the spillway is opened, the massive amount of fresh water, nutrients and sediment dramatically affects the ecosystem of Lake Pontchartrain and its surround-ing wetlands. When the spillway was opened in March 1997, releasing more than 3 trillion gallons of river water, a severe algal bloom was documented. A large percent-age of the extensive surface area of the lake was covered with blue-green algae, causing toxic and anoxic condi-tions which killed fish and macrophytic plants. This was warned against in 1927, even as the spillway was being designed, by Percy Viosca, citing speeded flow caused by the guide levees and the lack of existing wetland sys-tems to slow and collect excess nutrients before reach-ing the open water of the lake. The spillway water also carries industrial wastes, pesticides and changes the wa-ter temperature and salinity levels in the lake, increasing turbidity.[8] At the same time, the increased nutrients and sediments coming from the Bonnet Carré also benefit

Figure 7: Infrastructural and ecological networks of the Bonnet Carre Spillway.

Lake Pontchartrain by increasing fish and shellfish pro-duction, reducing salinity levels and increasing marsh-land production. Because of these findings, proposals have been developed to examine how the spillway can be modified to divert limited amounts of water from the Mississippi throughout the year. Freshwater diversion systems, unconnected with spillway systems, have been implemented by the Army Corps in other areas of the Lower Mississippi (as at Caernarvon) with the same goal. However, sparse data exists to confirm results of these diversions as of yet. The ecosystem of Lake Pontchartrain also infil-trates and transforms the spillway lands itself. The calm, secluded freshwater habitats within the spillway, offer an ideal nursery for aquatic populations. The spillway, with positive and negative effects has significantly altered the pre-existing ecosystem but the interaction between the two zones signals a need to work within this synthetic ecology, as with the proposed freshwater diversion.

Constructed Ecologies

Since the emergence of heroic engineering ‘problem solving’ as a response to crises related to nineteenth century and early twentieth century industrial urbaniza-tion and not unrelated natural disasters, we have seen a remarkable development of constructed urban land-scapes and public works typologies. Most were imple-mented with the aim of ‘conquering’ nature, disease,

or societal ills with rigid solutions that were suited to a single time and purpose. As part of this lineage, the Bonnet Carré Spill-way (7,623 acres) stands as a yet unidentified typology of constructed landscape, one that could be character-ized as an evolved soft system, or infrastructural ecol-ogy. The Bonnet Carré, as part of the Mississippi flood control system, is simultaneously highly engineered and indeterminate in its function and use, creating a dynamic landscape of adaptive stability, continually manufactur-ing new ecologies and environments. The planned “de-struction” or flooding of the spillway has enabled the growth of vital wetlands for coastal erosion control, rec-reation grounds and wildlife habitat. At first unplanned, the spillway has created unforeseen ecological, cultural and economic opportunities. What was envisioned sole-ly as a flood control system has evolved into a unique coastal strategy to revive estuarine dynamics, reshape urbanism, create regional economies, cultivate new life-styles, and restore coastal biodiversity. Taken together, (controlled) flooding becomes a mechanism of defense. Nature, no longer conceived as separate from urbanism, is fully integrated into the urban footprint.

Opportunistic Adaptation

The Bonnet Carré emerged out of crisis, a constructed landscape that directly addressed ecological and eco-nomic challenges of the Mississippi Valley. It has contin-

Figure 5 (below): Size comparison and construction (and reconstruction) dates of similar public infrastructural landscapes.

ued to do so as of the recent 2011 flooding while also cre-ating opportunities for citizens, environmental concerns, and increasingly administratively and financially restrict-ed public agences. Finding solutions that stimulate both economic opportunities and environmental rejuvenation is key to developing healthy cities. Here, adaptation of aging infrastructural networks provides perhaps the best opportunities for creating soft systems, as in the Bonnet Carré Spillway. When working at these large scales, it is impos-sible and counter-productive to attempt to control every aspect of the design. Constructed landscapes and infra-structures, such as the Bonnet Carré Spillway, illustrate the advantages for contemporary practitioners to be managers and strategists, as much as designers. In ad-dition to complexities of scale, contemporary distributed forms of urbanism are more entangled in their economic and ecological conditions and thus increasingly bound to the dynamic nature of each. Thus, the maintenance becomes critical of a broad network of stakeholders that can be engaged throughout the evolution of these sites. Understanding key flows of water, waste, energy, mobil-ity and food among regional landscapes allows us to develop spatial networks that react and evolve to both lo-cal and regional circumstances over time.[9] Leveraging such soft systems requires adaptation of performance-based and process-oriented strategies, rather than stat-ic, highly aesthetic and mono-functional solutions. Finally, could we imagine opportunities for con-structed landscapes that literally allow for the “irrigation of territories with potential?”[10] Waste is no longer a liability, but an essential building block for structuring new ecologies and economies of scale. Sites may work both technically and ecologically, as well as socially, fis-cally and administratively, allowing new soft systems to develop. Logical and bewildering. Inflexible and tightly controlled ‘solutions’ addressing a single constraint with a single client adapt to opportunities of multiple, interde-pendent uses and flexible structures.

Note

This article is part of an on-going research project concerning

the condition of flexibility, infrastructure, economy, and ecology

of which this case is one study. This case will be supplemented

by primary source research via the USACE which was funded

in part by a Penny White Research Grant from Harvard GSD.

All images included are by the authors unless otherwise noted.

Sources

1. “Mississippi River and Tributaries Project,” Army Corps of Engineers, accessed 15 November 2010, http://www.mvn.usace.army.mil/pao/bro/misstrib.htm.

2. United States Army Corps of Engineers: New Orleans District, “Bonnet Carré Spillway Master Plan” (USACE May 2009), accessed 10 November 2010, http://www.mvn.usace.army.mil/recreation/mp_without_appendi-ces.pdf.

3. Army Corps, “Bonnet Carré Spillway Master Plan”.

4.“The Mississippi Levee System and the Old River Con-trol Structure,” Katherine Kemp, last modified 6 Janu-ary 2000, http://www.tulane.edu/~bfleury/envirobio/enviroweb/FloodControl.htm.

5. James N. Miller, “Moving Oceans Inland,” Modern Me-chanics and Inventions, September 1929, 38.

6. Mississippi River Commission, “The Mississippi River & Tributaries Project: Controlling the Project Flood,” (MRC 2010), accessed 10 November 2010, http://www.mvd.usace.army.mil/mrc/pdf/MRT%20info%20paper.pdf.

7. Army Corps, “Bonnet Carré Spillway Master Plan.” This document is the working source throughout the discussion of the spillway’s auxiliary operations in the sections ‘Emergent Economies’ and ‘Soft Systems’.

8. Robert W. Hastings, The Lakes of Pontchartrain: Their History and Environments (University Press of Missis-sippi 2009), p143.

9. Pierre Bélanger, “Landscape as Infrastructure,” Land-scape Journal 28 (2009), 79-95.

10. Rem Koolhaas, “What Ever Happened to Urbanism?” in S,M,L,XL, ed. Rem Koolhaas, Bruce Mau, 959-971, New York: The Monicelli Press, New York, 1995.