Climate Defenses Will Help Keep Coastal Cities Afloat

The names–Andrew, Katrina, Sandy–are reminders of the devastating storms that hit U.S. shores every few years, claiming lives and causing billions in damage. But in many coastal cities, they can also serve as lessons in the crucial effort to guard against the increasing threat of climate change.

New Orleans finally made a long overdue investment in its flooding defenses after Katrina hit in 2005. The result is a new $15 billion, 130-mile levee system that allows the city to close 220-ton gates along waterways and pump water from the sewage system.

In New York City, after Sandy paralyzed the nation’s economic capital, officials approved a project known as the Big U to protect the southern half of Manhattan. The barrier serves as a sea wall, keeping water out of the city during storms, but its integrated, parklike design will also enhance the urban environment. The critical defense system has secured more than $500 million to begin construction in 2018–but much more will be needed to finish.

Up the coast in Boston, officials are considering a more straightforward barrier that could close off the city from dangerous swells in the wide Massachusetts Bay.

A wall would be futile in Miami, which rests on porous limestone and is filled with high-rise towers built at water’s edge. In any given year, there’s an approximately 1-in-125 chance that Miami will face a storm that causes at least $15 billion in damage. By 2100, the chances will grow to 1 in 30.

The solution in South Florida may require a wholesale rethinking of the region’s urban planning. Buildings need to be built on higher ground, systems relocated and some places abandoned entirely. It’s a strategic approach that requires reconciling current needs with future risks–and could serve as a long-term planning template for the rest of the nation.