Through much of its history New York had a working waterfront. Be it for passengers, cargo, fishing, or ship building, warehouses and other industries, the waterfront was a busy, stinky, messy place. As a result the poshest residences were usually built inland, think Park Avenue. Since the ports are no longer used for industrial purposes there has been a rush to build along the shore. As discussed in a long article in Sunday's Times, maybe riverside condos aren't such a great idea.

The problem? Global warming is driving up sea level. Five inches higher by 2030 and another couple inches by 2050. While that doesn't sound like much, a slightly higher sea level lets water from a storm surge travel much further inland. Couple sea level rise with a likely increase in the frequency and strength of storms, both tropical and nor'easters, and you greatly increase the risk of an infrastructure disaster. Allstate is already refusing to renew policies in metro New York because of storm vulnerability.

Did you ever wonder why the West Village has low buildings? Why does the Manhattan skyline take a dip between the Financial District and Midtown? The answer is sand and bedrock. Early skyscrapers needed to be built on bedrock close to the surface. Sand underlies much of downtown above the Financial District. If a storm surge pushes through the West Village it is going to scour the sand that supports lots of unreinforced buildings, causing them to collapse or otherwise be unusable. It's not just the West Village, Red Hook is mostly fill, Coney Island and the Rockaways are nothing more than semi-permanent barrier islands, all the islands within Jamaica Bay are only a couple feet above sea level, as are JFK and LaGuardia airports. Shown in the map above, is the storm surge estimated for a category 3 hurricane, roughly the size of Hurricane Katrina. All the places in blue would be overrun with water.

Shiny new glass buildings are also a problem. Under the current building code, windows have to withstand wind gusts up to 110 miles an hour. That's fine for a minor hurricane, but it offers little protection in a major storm.

To deal with these problems the mayor has set up PLANYC, the Office of Long-Term Planning and Sustainability.

The options for holding back the sea are not pretty. A seawall would have to be dozens of feet high. A wall that high needs to be really wide. Good-bye river views and access!

A set of storm surge barriers, moveable, underwater locks that would be put into use ahead of an approaching storm will offer partial protection. According to SUNY-Stony Brook researchers there would have to be four barriers: under the Verrazano Bridge, between Staten Island and New Jersey, between Long Island Sound and the East River, and across the Rockaway Inlet. Barriers like this are expensive, $10 billion each, but that is a small investment if it protects trillions of dollars worth of infrastructure.

Other ideas PLANYC2030 are considering include requiring buildings to be retrofitted, and more appropriate land-use planning, including buffers to absorb the impact of storm surges. A draft revised building code is to be released this spring. Expected changes include requiring stronger windows and strengthening of critical buildings, such as hospitals, in flood zones.

Storm surge map from NASA and based on the work of the NYC DEP, SUNY Stony Brook, and FEMA.