topography

Many New Yorkers who are lucky enough to gaze at waves lapping on a beach near their homes pay a price for the view.

Maps provided by the city’s Department of Buildings show that coastal sections of Queens, Staten Island and Brooklyn are in “special flood hazard areas.” Practically all of Coney Island, much of the Rockaways, the Long Island Sound-hugging strip of the Country Club neighborhood of the Bronx, and the southeast coast of Staten Island are all edged in the dotted blue that, on the city’s maps, signifies susceptibility to major flooding.

In contrast to its experience in some suburban areas, FEMA had an easy job remapping New York. By 2005, the city had produced digital maps that imposed a fine grid over the city’s topography and supplied, for each box of the grid, the average elevation. FEMA analyzed the data using its own formulas, which account for factors like wave action, rainfall and soil permeability, and came up with a mathematical prediction of the chances of that elevation succumbing to a catastrophic flood. The mapping was declared complete in 2007, and homeowners were notified if they were in the flood plain.

Officials for FEMA said they could not pinpoint how many New York properties were placed in the flood zone for the first time, nor how many were removed, because the New York remapping was completed before such tabulations were made. But they also said there were probably few actual changes in New York because its highly regarded maps had already revealed to its homeowners which of them were at risk.