In NYC, the last time that the East River touched the Hudson River (see below) was on September 3, 1821 when a hurricane struck directly and the tide rose 13 feet in one hour. Should the city plan for it to happen again?
Along its 520 mile long coastline, New York’s waters have eased upward at an inch a decade, a rate that some say is accelerating. If so, by 2050, another 2 feet might be added. Although not below sea level, New York is vulnerable. A direct hurricane hit could mean subways flooded for weeks, basements inundated, electricity out, undrinkable water, commuter transport lines incapacitated.
Assessing the unlikely probability that a massive storm would directly hit New Orleans, in 1978, economists recommended a relatively low level of levee protection. Using rational cost benefit analysis, the question was where to allocate the city’s limited resources. They had no crystal ball–just some logical decision making that did not work out.
New York has some of the same dilemmas. When it equips subways with better flood protection like higher ventilation grates, then the same money cannot be used for new subway cars. Consolidated Edison says it would need $250 million for submersible switches and above ground high voltage equipment and other flood appropriate retooling. Green roofs? Sea gates? Water permeable bike paths? Stop all waterfront development? They did install porous riprap rock in Brooklyn. (???I have no idea what this is but the name is great).
You see where this is going. If a catastrophic storm hits the city, people might say the cost was immense. However, using classic opportunity cost reasoning, don’t the benefits of minimal action outweigh any benefits we enjoy if we mobilize for the storm of the century now?
This NYC site has a complete hurricane history for the city. Most of my facts about the city’s planning for a devastating flooding event are from this NY Times article. Also, I suggest looking at this EconLife post on cost benefit and pre-Katrina planning. Looking at this Congressional Report on Hurricane Katrina might provide more insight about current NYC decisions and Japan’s lack of planning for her recent nuclear plant catastrophe.
When the 1831 storm hit, the East River, extending down the right side of Manhattan met the Hudson River located west of the city.