Hurricane Katrina is estimated to be the largest natural disaster in U.S. history (Figures 1 and 2), killing more than 1,800 people and causing tens of billions of dollars in damage. Massive resources will go towards the restoration of New Orleans and the Mississippi delta. While some have argued that it does not make sense to rebuild New Orleans at all, given its highly vulnerable location, others have raised broad questions about how the city and region should be restored. It is clear that enormous public resources are going to be spent and some form of rebuilding is going to occur, not least of all because the Mississippi River in the New Orleans region is home to the largest port in the nation and one-quarter to one-third of oil and gas used in the nation is either generated or shipped through the north central Gulf. So, the real question is not if but how it should be rebuilt. There are two broad options: (1) essentially replace what was there before; or (2) use this tragedy as an opportunity to create something substantially different and better.
Option 1 seems to be largely the direction being taken so far. The Army Corps of Engineers has been actively working to rebuild the levees to their pre-storm status of being able to withstand a Category 3 hurricane and there is discussion of rebuilding all of the levees to withstand a Category 5 hurricane and even of building a Category 5 levee system across most of the Louisiana coast. There is already serious doubt as to whether a rapidly reconstructed levee will provide the needed protection and even if the rebuilding is successful, it will merely be setting the pins up to be knocked down again by a future, even larger hurricane. In addition, the increasing cost of energy will probably make such a levee system unsustainable. In the meantime, the city of New Orleans faces a combination of worsening problems, including: (1) likely increases in intensity of tropical storms due to global warming; (2) the continued sinking of the city due to land subsidence and sea level rise, albeit at a slower pace than in the past; and (3) the continued destruction of the coastal wetlands that serve as the city’s storm protection barrier (in addition to the many other ecosystem services they provide).
Option 2 seems to be the only viable and sustainable option, but it has so far received little serious attention. This article elaborates on a substantially different vision of a truly new New Orleans – one that can provide a sustainable and high quality of life for all its citizens, while working in partnership (not in opposition) with the natural forces that shaped it. This New Orleans can also serve more generally as a model for sustainable development.
That New Orleans would be devastated by a major hurricane was unfortunately both predictable and predicted. It was clear from studies published in the past 50 years that New Orleans was becoming more vulnerable with each passing year. The wetlands surrounding New Orleans provide protection from storm surges. These wetlands area result of 6 millennia of land building but they have been lost at an average rate of 65 km2 (~25 mi2) per year since the turn of the century (Figure 3). The barrier islands were rapidly eroding as well. Almost 5000 km2 (1800 mi2) of coastal wetlands have been lost since the 1930s, and the situation has continued to deteriorate. Figure 4 shows the loss of coastal wetlands projected to occur by the year 2050. This forecast was made before Hurricane Katrina, and 100% of the projected loss actually occurred during the storm.
The cause of this dramatic land loss was a combination of natural and human forces. For millennia, the natural process of geologic subsidence was counterbalanced by riverine inputs into a deltaic plain characterized by natural hydrology. However, in the 19th and 20th centuries, there was a massive disruption of the hydrology of the delta. Riverine input was drastically reduced by the creation of levees, and the closure of distributaries and the internal hydrology of the delta were pervasively altered, mainly due to canal dredging for oil and gas exploration and extraction. As a result, the blanket of freshwater, sediments, and nutrients from the Mississippi River basin that used to spread across the delta is no longer there. The heavily managed Mississippi River was forced to dump most of its load off the continental shelf into the deep waters of the Gulf of Mexico and the wetlands deteriorated due to canal dredging, subsidence, and saltwater intrusion.
The Atchafalaya River, a branch of the Mississippi River that now carries one-third of the Mississippi’s flow, discharges into shallow waters of the delta and has both built new deltaic lands and protected a large area of existing wetlands along the central Louisiana coast. The history of the Atchafalaya delta shows that appropriately managed river discharges and hydrologic restoration (by removing canal spoil banks) can result in net marsh creation and counteract the forces of land loss.
The mainstem Mississippi River was managed to allow deepwater shipping and commerce in the New Orleans region and throughout the Mississippi basin, as well as to impede flooding of developed areas, but this management regime ultimately led to the situation that made New Orleans so vulnerable. The net result has been that the people who lived below sea level in New Orleans were in more danger every year from: (1) the potential for river flooding; (2) the disappearance of surrounding wetlands due to both restriction of river input and internal hydrological alterations; and (3) the deteriorating levees, which were under continued strain due to age and increasing hydrologic demands. So, what happened in New Orleans, while a terrible “natural” disaster, was also the cumulative result of excessive and inappropriate management of the Mississippi River and delta, inadequate emergency preparation, a failure to act in time on plans to restore the wetlands and storm protection levees, and the expansion of the city into increasingly vulnerable areas. Many of the areas that are now below sea level (Figure 5) were not always so. Up until the first quarter of the 20th century, most of the city was above sea level, either on the natural levee of the river or on older ridges formed by earlier courses of the river. However, the drainage of the wetlands between the natural levee along the Mississippi River and Lake Pontchartrain promoted soil oxidation and rapid subsidence (Figure 6) in many parts of the city.
Increasing the area of coastal wetlands through ecological engineering provides a very cost-effective and sustainable approach for providing hurricane protection to human settlements in coastal Louisiana. Wetlands will provide an important and sustainable buffer against storm surges and wave action generated by tropical storms and hurricanes. Coastal ecosystems such as marshes and forested wetlands, whether naturally occurring or ecologically engineered, play a significant role in reducing the influence of hurricanes and even tsunami waves. The mechanisms involved include decreasing the area of open water (fetch) for wind to form waves, increased drag on water motion and hence the amplitude of a storm surge, a reduction in direct wind effect on the water surface, and direct absorption of of wave energy.
While few experimental studies or modeling efforts have specifically addressed the effect of coastal marshes on storm surges, anecdotal data accumulated after Hurricane Andrew in 1992 in Louisiana suggested that storm surge was reduced about 4.7 cm/km of marsh (3 in/mile of marsh). Extrapolating from this number, a storm tracking from the south of New Orleans through existing coastal marshes could have its surge reduced by 3.66 m (12 feet) if it crossed 80 km (50 miles) of marsh before reaching the city.
Since marsh plants hold and accrete sediments, often reduce sediment re-suspension, and consequently maintain shallow water depths, the presence of vegetation contributes in two ways: first by actually decreasing surges and waves, and also by maintaining the shallow depths that have the same effect. Because wetlands indicate shallow water, the presence of wetland vegetation is also an “indicator” of the degree to which New Orleans and other human settlements are protected.
What do we want to restore?
Before discussing options for restoring New Orleans, we need to consider what we are trying to restore and why. The conventional approach to economic development focuses only on the market economy – the value of those goods and services that are exchanged for money. The purpose is usually taken to be to maximize the value of these goods and services – with the assumption that the more activity, the better off we are. Thus, the more GDP (which measures aggregate activity in the market economy), the better. However, the purpose of the regional economy should be broader – to provide for the sustainable well-being of people. That goal encompasses material well-being, certainly, but also anything else that affects well-being and its sustainability. Moreover, there is a substantial amount of new research that demonstrates the limits of conventional economic income and consumption in contributing to well-being. In addition, there is growing evidence that ecological systems produce a range of services that support human well-being. Ecosystem services occur at many scales, from climate regulation at the global scale, to flood and storm protection, soil formation, fisheries, nutrient cycling, recreation, and aesthetic services at the local and regional scales. It has been estimated that the annual, non-market value of the Earth’s ecosystem services is a great deal larger than global GDP.
So, if we want to assess the “real” economy – all the things which contribute to real, sustainable, human well-being – as opposed to only the “market” economy, we have to measure the non-marketed contributions to human well-being from nature, from family, friends, and other social relationships, at many scales, as well as from health and education. One convenient way to summarize these contributions is to group them into four basic types of capital that are necessary to support the real, human well-being-producing economy: built capital, human capital, social capital, and natural capital.
Coastal wetlands in Louisiana have been estimated to provide $940 ha–1 yr–1 ($375 ac–1 yr–1 – these and all subsequent figures have been converted to 2004 US dollars) in storm and flood protection services. Restoring Louisiana’s coastal wetlands and New Orleans levees has been estimated to cost about $25 billion. Had the original wetlands and other natural features, such as barrier islands and natural ridges, been intact and the levees in better shape, a substantial portion of the $100 billion plus damages from this hurricane would have been avoided. Prevention would have been much cheaper and more effective than reconstruction. In addition, the coastal wetlands provide other ecosystem services which, when added to the storm protection services, are estimated to be worth about $12 700 ha–1 yr–1 ($5200 ac–1 yr–1). Restoring the 4800 km2 (480 000 ha) of wetlands lost prior to Katrina would thus restore $6 billion yr–1 in lost ecosystem services, or $200 billion in present value (at a 3% discount rate).
Seven principals for the restoration of New Orleans and coastal Louisiana
The natural, built, human, and social capital assets of New Orleans have been radically depleted and need to be rebuilt. We can recreate the vulnerable and unsustainable city that was there before, or we can reinvent New Orleans as a new model of a sustainable and desirable city of the future. Here are some elements of a truly sustainable vision, based on ecological engineering and economics.
- Let the water decide. Building a city below sea level is always a dangerous proposition. While parts of New Orleans are still at or above sea level, much of it had sunk well below sea level since the first quarter of the 20th century. It is not sustainable or desirable to rebuild these areas in the same way they were before. They should either be replaced with wetlands that are allowed to trap sediments to rebuild the land (see below), or replaced with buildings that are adapted to occasional flooding (i.e., on pilings or floats). Wetlands inside the levees can help clean waters, store short-term flood waters, provide habitat for wildlife, and become an amenity for the city.
- Avoid abrupt boundaries between deepwater systems and uplands. Gentle slopes with barrier islands, shallow waterbodies, wetlands, and natural ridges are the best division, and avoid putting humans, particularly those who have few resources to avoid hydrologic disasters, in harm’s way. The abrupt boundaries of the levees are necessary, since natural features such as wetlands and barrier islands alone cannot protect the city, but we need to use both, as appropriate. The idea of avoiding abrupt boundaries is included in the idea of multiple lines of defense, where all of these features are integrated into a comprehensive flood protection system.
- Restore natural capital. A healthy economy requires a balance of built, human, social, and natural capital. Because of its enormous size (about 25 000 km2) and productivity, the Mississippi delta is perhaps the most concentrated area of natural capital in North America. This is reflected in the largest fishery and most important flyway terminus in the U.S., abundant fish and wildlife, high water cleansing ability, and high storm protection services. As discussed earlier, restoring the 4800 km2 of wetlands lost prior to Katrina would provide a host of valuable ecosystem services, worth roughly $6 billion yr–1, or $200 billion in present value (at a 3% discount rate).
- To do this we should use the resources of the Mississippi River to rebuild the coast, changing the current system that constrains the river between levees. Diversions of water, nutrients, and sediments, such as those envisioned in the LCA plan, should be greatly expanded in order to allow more rapid restoration of the coastal wetlands. Levees are necessary in some locations, but where possible the levees should be breeched by structures in a controlled way, to allow marsh rebuilding. Reopening old distributaries and crevasse formation are two additional ways to reconnect the river to the deltaic plain. The reconnection of the river should be integrated with other features, such as barrier island restoration, wise use of dredged sediments, and extensive canal and spoil bank removal, to develop a comprehensive restoration plan. Other restoration resources, such as treated municipal effluent and upland runoff, should also be used.
- Restore the built capital of New Orleans to the highest standards of high-performance green buildings and a car-limited urban environment, with high mobility for everyone. New Orleans has abundant renewable energy sources in the form of sun, wind, and water. What better message than to build a 21st century sustainable city, running on renewable energy, on the rubble of a 20th century oil and gas production hub.
- Rebuild the social capital of New Orleans to 21st century standards of diversity, tolerance, fairness, and justice. New Orleans has suffered long enough with social capital dating from the 18th (or even the15th) century. To do this the planning and implementation of the rebuilding must maximize participation by the entire community. This will certainly be difficult for a number of reasons, including the historical antecedents of racism and classism in the region, and the fact that much of the population has been forcibly removed from the city. Yet it is absolutely essential if the goals of a sustainable and desirable future are to be achieved.
- Finally, we should restore the Mississippi River Basin to minimize coastal pollution and the threats of river flooding in New Orleans. Upstream changes in the 3 million km2 Mississippi drainage basin have substantially changed nutrient and sediment delivery patterns to the delta. Changes in farming practices in the drainage basin can improve not only the coastal restoration process, but also improve the nation’s agricultural economy by promoting sustainable farming practices in the entire basin.
The restoration of New Orleans and the rest of the Mississippi delta can become another expensive disaster waiting to happen, or it can become a model of sustainable development. If it is the latter, it could be a truly unique inspiration to billions of people around the world. What better way to say to the world “look at what can be accomplished” than to create a sustainable and desirable city, shining like a jewel on the Mississippi, where all the streetcars run on renewable energy and are named “desirable.”
This entry is adapted from Robert Costanza, William J. Mitsch, and John W. Day Jr., A new vision for New Orleans and the Mississippi delta: applying ecological economics and ecological engineering Front Ecol Environ, 2006; 4(9): 465–472.
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