Wet and Wetter

Location really is critical in proximity to coastlines, and to the objective measuring stick of the geodetic vertical datum, the zero elevation.  The denizens of New York City learned this harsh lesson in 2012, on the receiving end of the same damaging forces more typically experienced by coastal residents from Bangladesh to the Netherlands.  Hurricane Sandy was unusual in many ways – late-season, upper Atlantic location – but the force carried by wind and water were the standard hurricane fare.  In New York, storms like this happen so infrequently and unpredictably as to make designing a plan of resistance for homes or small buildings uneconomical.  However, when the financial capital of the world is crippled by storms, it is useful to consider whether some hardening of the infrastructure systems might be practical.

Water finds the cracks and basins in the urban system.  Rain celebrates a flight of stairs leading down into the earth, an opening to below, an invitation to sweep detritus along with it to return to the filtering sands beneath our manmade crust on top.  An open escalator, a ventilation grate, a bank of turnstiles – these offer no barrier to water.

New York City transportation systems failed as spectacularly as the electrical grid.  Five million riders a day use the subways.  On a fine day, 13 million gallons of water are pumped out of tunnels, primarily rainwater, and the ubiquitous flow of sidewalk- and street-cleaning that enters through subway vents.  On a wet day, the systems can barely keep up.  There is no extra capacity for storms or superstorms, which bring in not just water but introduce salt water, corrosive and conductive, into this electricity-dependent subterranean world.  “Because city officials are not in the business of advertising their concerns, most New Yorkers don't realize that some have been imagining this scenario for a while. The culprit, some say, could be climate change. To be sure, New York faces unprecedented dangers in a warming world. Although the waters along the east coast of the United States have been inching up since the end of the last ice age, the rate of rise has accelerated in the last 150 years. This is particularly true in places like New York, where land is also subsiding as the Earth's crust readjusts. If polar ice sheets continue to melt at their current rate, the water around Manhattan and Long Island could rise by five inches within the next eight years. By mid-century, local sea level could be up by a foot, and up by two feet by 2080.”[i]

This financial capital is sounding more and more like the world trade center of a thousand years ago.  Venice may have defined trade in the twelfth century, but its susceptibility to encroaching waters has affected the city’s stability as a financial powerhouse since then.  If engineers can’t keep the water out, the beautiful palaces will continue to crumble, the floating hummocks sink, and the city disappear beneath the waves, a modern Atlantis. Against modern threats, cities including Rotterdam, Venice, and London are creating new types of water barriers at the mouth of rivers and estuaries.  These mechanisms address rising sea levels, storm surge and flooding, especially under the influence of extreme weather patterns.

As global weather patterns tip from the predictable to the extreme, coastal fortifications against hazards will increase.  The catalog of proposed measures is long and expensive: bulkheads and bulwarks, drowned reefs of subway cars, restored wetland fringes, wave attenuators, pervious streets, rainwater bladders, harbor barriers, flood gates, sea gates, all manner of gates, oyster reefs, inflatable balloon dams, et cetera.  The force of water is impossible to resist.  Venice learned this long ago, although elegant efforts valiantly extend the city’s lifeline.  Will other coastal centers of finance and trade – New York City, London, Tokyo, Hong Kong – learn these lessons before they also succumb to the waves?

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[i] Jesse Newman, “For New York's Subway, Sandy's Devastation May Be Just the Beginning.”  The Atlantic, Nov 1 2012.