urban ecology and design laboratory

Of Storm Surges and Sea Changes: Urban Adaptation to Rising Waters

The following editorial is written by Katharine Gehron, Timothy Terway and Alexander Felson,

Kate is a master’s student, Tim is a PhD student and Alex Felson is a assistant professor at the Yale School of Forestry & Environmental Studies and the UEDLAB Contact Kate here.

The public and private infrastructure that underlies metropolitan life—sprawling, reticulate, the product of massive amounts of labor and investment—is essential to public health and stable civic life. We depend on it continuously, yet it is largely invisible until it is compromised. Events such as power-grid failures, road and rail impasses, port closures, and drinking-water contamination are potentially catastrophic and quickly produce states of emergency. 

Extreme weather events related to climate change pose grave threats to urban infrastructure, especially in densely settled coastal cities, where millions of people depend on clean running water, transportation corridors, and other services that are produced or provided near sea level, which is predicted to rise between 3 and 6 feet in the next hundred years (Vermeer and Rahmstorf 2009). The extensive damage caused by Hurricane Sandy is likely a sign of things to come, as other extreme weather events of recent years suggest that we are already experiencing the effects of climate change. Coastal cities are home to our most important economic centers and to a disproportionate fraction of the population. We must find ways to mitigate the damage that is sure to be visited upon the most vulnerable, low-lying zones. 

We can do this by way of three major approaches: the construction of hard infrastructure such as sea walls, the implementation of “green” infrastructure such as engineered wetlands, and retreat. The first approach involves top-down coordination and significant expenditure of public funds; the second may be more bottom up and may be implemented over time by various alliances between civic groups, nonprofits, the private sector, and government; and the third depends on the ability of insurance companies, FEMA, and homeowners to develop mutually agreeable arrangements that lead to a coordinated response, not conflicts about property that result in gridlock. 

Each approach requires very different actions and decisions on the part of the city, regulators, and homeowners, with different associated costs. Hard infrastructure may permit cities to avoid the necessity of tearing down their most flood-prone structures, which may protect neighborhoods as well as business districts. However, hard infrastructure is expensive to build and maintain, and it may fail with little warning, and with serious consequences, especially for people who lack the resources to move out of harm’s way. (The breach of the levees during Hurricane Katrina visited far more tragedy upon poor minorities in New Orleans than it did on those with means.) If we build extensive hard infrastructure, how likely is it that we will learn from the past and distribute risk more equitably? That we will plan for failure? Even if we succeed at these things, the construction of walls and other structures to hold back the sea will take years and will not address short-term exigencies. 

The implementation of green infrastructure can be integrated into planned, or managed, retreat from the shoreline, through the replacement of structures and open space with engineered tidal wetlands. While this concept has been accepted in Great Britain and the Netherlands for some time now (see, e.g., French 2006), it is a somewhat shocking and new approach in the U.S.; a recent article in the New York Times described this strategy as “apocalyptic” (“Protecting New York City, Before Next Time”). Is it? Current sea level rise projections suggest that planned retreat from rising seas, in conjunction with the establishment of salt marshes, is a practical and sustainable response to a process that is already under way. Yet for the wave attenuation function of the marshes to be significant, a wide expanse of the shoreline will likely have to be converted to marsh. It is unclear whether enough urban land could be set aside, whether through voluntary sale of private property (inefficient and unlikely) or government fiat (a political hornet’s nest), to create sufficient marshland to make this option feasible.

Some of these tensions and problems are reflected in the contributions to “Rising Currents,” a 2010 MoMA exhibition organized by the museum’s curator of architecture and design, exhibited the responses of several teams of architects and landscape architects to design challenges produced by sea level rise in New York City, an issue that has heretofore been largely neglected, as is clear in the remark of one tenant of a flooded office building following Hurricane Sandy: “We had prepared for an emergency. The emergency we had prepared for was an act of terrorism, not this” (“Future Is in Limbo for the Damaged Buildings Close to the Water’s Edge”).

Each team contributing to “Rising Currents” proposed a design solution for a different section of New York Harbor. “A New Urban Ground,” prepared by dlandstudio and the Architecture Research Office, proposes retrofitting the shore of Lower Manhattan with engineered wetlands that would protect this part of the city from tides that, in coming years, may inundate (according to the project numbers) a fifth of the region at high tide and more than half of the region during extreme storm surges. Can modifications to the shoreline buffer the sea? These wetlands are intended to absorb stormwater, reduce wave height and force, and reduce erosion. However, research on the benefits of wetlands for wave attenuation is limited, and the depth of wetlands required is typically greater than what is currently available. The proposal also calls for porous streets that would absorb stormwater and help to reduce the amount of flooding that would occur on impervious concrete. Pipes carrying sewage, water, gas, and electricity would remain buried but would be placed in a waterproof enclosure. Flood mitigation and the waterproofing of sewer lines would help reduce water contamination resulting from combined sewer overflow during extreme storm events, a longstanding problem, but the replacement of substreet pipes with waterproof, insulated pipes would be very expensive and disruptive. It seems that the ideas presented in the proposal are a good start to a necessary conversation but in need of further critical analysis and especially engagement with local populations and stakeholders, as well as city officials. 

Such civic engagement is an essential part of coastal adaptation planning, a process that raises some difficult social issues. Who will stay along the shoreline by choice, and who by necessity? What will the distribution of risk be like, and will we, as a society, help those with few resources find new places to live at higher elevations? What will be the costs of such dislocations to community coherence and civic identity? The questions raised by the prospect of retreat are disturbing and complex. By underestimating the scale of sea level rise and attempting to hold it off primarily with fortifications, we may end up spending great sums of public money to build structures that may not be able to withstand the stresses that will be placed upon them and that may therefore fail, creating particularly disastrous results for underprivileged communities To adapt to sea level rise in cities, we will need civic collaboration across scales, from the federal government to neighborhood groups, of a kind with midcentury wartime efforts, when citizens grew their own food in victory gardens, saved metal scraps, and worked together in ways both large and small to respond to a crisis. We may need to balance the construction of large-scale hard infrastructure with local efforts to green the coastline.

It remains an open question whether such an integrated enterprise is possible—whether opposing interests will splinter fragile coalitions and create secondary conflicts that complicate the primary issue, or whether factions will manage to reconcile in order to solve urgent problems through the formation of new social (and physical) structures in a changed world. Contemporary civic discord suggests there will be plenty of conflict in coming years over property rights, government assistance, public spending, and other issues related to states of emergency and natural disasters. Time will tell.

-Katharine Gehron

References:

Vermeer, M., and S. Rahmstorf. 2009. Global sea level linked to global temperature. Proceedings of the National Academy of Sciences of the United States of America 106(61):21527–21532.

French, P. W. 2006. Managed realignment: The developing story of a comparatively new approach to soft engineering, Estuarine Coastal and Shelf Science 67(3):409–423.

Feuer, Alan. “Protecting New York City, Before Next Time.” New York Times, November 3, 2012. Accessed 11/28/2012. http://www.nytimes.com/2012/11/04/nyregion/protecting-new-york-city-before-next-time.html?pagewanted=all.

http://www.moma.org/explore/inside_out/category/rising-currents

Kleinfield, N.R. “Future Is in Limbo for the Damaged Buildings Close to the Water’s Edge.” New York Times, November 5, 2012. Accessed 11/28/2012. http://www.nytimes.com/2012/11/05/nyregion/damage-unclear-future-in-limbo-for-some-buildings-in-lower-manhattan.html?pagewanted=all.