What are some of the lessons that Sandy teaches us about the way we build?

Almost two weeks after Sandy struck, my wife and I got our heat and hot water back; electric power had returned a few days earlier. Our apartment in Lower Manhattan relies on the Con Edison steam system, not a boiler; the utility's slow repair process was the source of the lag between the restoration of power and the return of heat. In both cases, though, we had relied on a centralized technology, rather than a distributed one, which raises fundamental questions about how we conceptualize and deploy necessary infrastructure. As we rebuild, we must be alert to the susceptibility of massive systems to massive failure.

If you remove the areas most at risk of flooding (pink in map, top), you get the original outline of Manhattan (map, above).

Sandy's misery–and risk–were unevenly distributed. Of course, the greatest damage occurred in the lowest-lying areas of the city, where homes were flooded and swept away. Up on the 16th floor of our apartment building, we were inconvenienced; but having to travel uptown to shower and use the Internet was hardly comparable to the real tragedies suffered by so many. And, because we live in a zone of privilege, the police were everywhere. The situation was very different in the city's public-housing projects–where more than 400 buildings were affected and where, two weeks after the storm, over 15,000 apartments remained without heat, hot water, or power.

It is clear to rational observers that the seas are rising, that the frequency and energy of storms are increasing, and that we're desperately unready. In many ways, New York was less prepared for Sandy than New Orleans was for Katrina. Although its system was inadequate and failed spectacularly, the pumps and levees of New Orleans were a longstanding acknowledgment of the topographic and hydrological facts of a situation known to be parlous. While New York has marshaled far greater financial, material, and leadership resources, and shown instances of remarkable resilience (the badly flooded subways came back amazingly fast), it has done almost nothing to plan for the re-contoured reality of climate change. We are only slowly recognizing that it's a problem we've brought on ourselves by the way we've built. A map of Lower Manhattan reveals that the area of greatest danger is precisely the territory created by fill (beginning in the days of 17th-century New Amsterdam), further evidence of the substantially anthropogenic causes of the flood.

The problem can be addressed only by actions that offer both behavioral and physical solutions. Tunnels must be protected, barriers built, wetlands restored and constructed, attenuating shoals inscribed, pavement made porous, and equipment such as generators and fuel supplies elevated or otherwise secured. The economics are clear: Our failure to protect our lowlands will cost, just for Sandy, perhaps $50 billion, and the cost curve for repair has surely crossed the one for protection. At NYU Langone Medical Center on the East River–which had to close when its generators failed and its belowground MRI machines were destroyed–the damage may be up to $1 billion. We are now forced to think, as New Orleans did, about environmental triage, about the necessary dialectic of protection and abandonment, a problem that far exceeds actuarial calculation.

This nexus locates the social dilemmas of environmental transformation. In New York, we must ask whether working-class shore communities–such as the Rockaways in Queens and Midland Beach on Staten Island–have become our Lower Ninth Wards. How will we balance the claims of culture and community against the severity of the risk and the lifestyle economics of relatively low-density settlement on a fragile shore? It seems certain that we will protect, rather than abandon, the global assets of Lower Manhattan. But an examination of the 600 miles of New York's coastline will surely demand serious, even radical, thinking about a broad range of protective tactics, from massive Dutch-style defenses to softer forms of naturalization to strategic withdrawal. These decisions will play out along lines that will not simply be technical but will focus the values that underlie the very idea of community, the meaning of mutuality.

Perhaps the most symbolically fraught damage caused by Sandy was the flooding of the 9/11 Memorial, the preeminent marker of the form of risk that has dominated our thinking for the past decade. It's often remarked that generals always prepare to fight the last war. It's time to recognize that we can no longer focus such disproportionate resources on yesterday's risks. Let us hope that the poisonous anti-government and anti-environmental politics of today do not prevent us from using our peace dividend to solve this urgent threat.