Want to flood-proof Manhattan? It’ll cost at least $11.6 billion

Key landmarks are shown in yellow. Sites of potential flood barriers are in red.

John Timmer

Want to make Manhattan waterproof? A few years ago, the idea seemed ludicrous to everyone but a handful of researchers and urban planners. But the aftermath of Hurricane Sandy, extended outages, and infrastructure damage changed the conversation. Suddenly, long-ignored plans for multi-billion-dollar flood barricades were given serious attention.

But does it merit the attention? In today's issue of Science, researchers describe a risk assessment model that they use to consider a variety of approaches for flood-proofing the Big Apple. They conclude that, for now, adaptation makes more economic sense than a giant flood barrier—but that may change. Under a middle-of-the-road climate scenario, where storm intensity and ocean levels both rise, building a barrier starts to make sense before mid-century.

Options

The authors of the new study (who are scattered among four different academic institutions) focus on a number of different plans for minimizing the impact of floods. At the low end, the city would simply harden key pieces of infrastructure, like the subways, airports, and electrical generation and distribution sites. Accompanying that would be changes in the building codes requiring that buildings elevate above common flood levels and/or incorporate basic levels of waterproofing. Since New York has a massive existing stock of buildings, some effort would also have to be made to compel changes in that.