The death toll still incalculable, the suffering unimaginable, the recovery plan unclear, the preparations inadequate – the destruction of the city of New Orleans at the hands of Hurricane Katrina has shaken the nation.

In the era of terror, our emergency preparations are focused on confronting man-made disasters – but we have fresh evidence that natural disasters can sometimes deliver a September 11-like punch, leveling not just buildings but a city.

New York City is not immune. While generally blessed from a geographic standpoint – the fault lines that run below the city’s bedrock are essentially dormant; tornadoes, forest fires, and floods are not frequent problems – history shows that some hurricanes have hit our city in the past, to deadly effect.

In 1938, a hurricane claimed the lives of 600 when it hit New England, including 10 deaths in New York City. The threat only grows more acute as some scientists worry that a warming Atlantic Ocean could make it easier for hurricanes to reach this far north.

And we have all to clear an idea of the danger once such a hurricane arrives. If a Category 2 storm hit New York City, Lower Manhattan would be under 6 feet of water. A stronger Category 3 or 4 hurricane hitting just north of Atlantic City could cause the deadly northeast curve of the storm to slam into what is called “the New York bite” – the right angle where Long Island juts out from the mainland, with New York City in the corner. The narrow mouth of our harbor could act as a funnel for the storm surge, focusing and then briefly trapping the rising wall of water in the bay.

A 1990 study by the Army Corps of Engineers expressed concern that exceptionally tall bridges such as the Verrazano-Narrows and George Washington could be exposed to hurricane-strength winds blowing at higher speed than at sea level, severely disrupting evacuations. In addition, there is the likelihood that a Category 4 could place John F. Kennedy Airport and the surrounding area beneath 20 feet of water, while also severely flooding the Holland and Brooklyn-Battery tunnels.

Subways provide another unique challenge for New York in a strong hurricane scenario – the 468 miles of underground tunnels that stretch across the city could flood easily and almost immediately. The electrified third rail would have to be shut down in advance, with subway cars removed to a safe area to avoid being tossed around tunnels and city streets like children’s toys.

Such a scenario came closest to occurring when the sixth-costliest hurricane in American history hit Long Island in September 1938, causing damage that exceeded $18 billion in today’s dollars. Power was knocked out throughout the city for days, more than 100 large trees were upended in Central Park, and subway service was suspended. But overall the city got off easy, with the eye of the storm passing 50 miles to the east, causing extensive devastation in New England.

Survivors of the 200-mile-a-hour storm recounted seeing a 25- to 40-foot “fog bank” rolling toward the coast. This “fog bank” turned out to be the murderous wall of water associated with a storm surge moving forward at 60 miles an hour.

Lesser storms have made their mark on our city as well – an 1821 hurricane passed directly above Manhattan, causing the Hudson and East rivers to meet at the aptly named Canal Street. A relatively modest Category 1 hurricane in 1893 completely destroyed a resort island named Hogg Island in the Rockaways, off the coast of Queens.

We forget these past storms at our peril, as we can see from the calamitous results of the complacency of New Orleans in the face of its own history. New Orleans is in the Gulf stream storm belt, making it especially vulnerable, yet the levy system was not adequately reinforced. In September 1915, another deadly hurricane made landfall at Grand Isle, the same place where Katrina came ashore.

New York’s leaders understand the importance of planning. Just two weeks ago, the city’s Office of Emergency Management performed a tabletop drill imagining what would happen if a hurricane hit the city. Among their conclusions: Evacuations would have to begin at least a day in advance for those living in lowlying areas.

Since New Yorkers think more about proximity to subway stops or local landmarks than whether their neighborhood is a “low-lying area,” the emergency office’s Web site at nyc.gov/oem offers a way for residents to type in their address to determine the likely impact on their home of a hurricane and consequent flood.

The emergency management office’s Urban Search and Rescue Team is at New Orleans assisting in a mammoth rescue and recovery effort that will likely take months. As that effort continues, New Yorkers should understand that hurricanes are not distant afflictions that only hit the south.

Pop culture recognized the danger to New Orleans, as attested by one of my favorite songs, Randy Newman’s “Louisiana 1927” – an unofficial state anthem of sorts, recorded in the 1970s:

“The river rose all day
The river rose all night
Some people got lost in the flood
Some people got away all right
The river have busted through clear down to Plaquemines
Six feet of water in the streets of Evangeline
Louisiana, Louisiana
They’re trying to wash us away.”

New York has also been warned. Hurricane history may be our best guide to the future.