NEW YORK — Nearly 3 million New Yorkers' homes are now in evacuation zones that cover more than a third of the city's population, under new maps released Tuesday.
In the wake of Superstorm Sandy, officials said last month, the number of zones would double and encompass about 600,000 more residents. Few storms are likely to require evacuating all six new zones, and the scheme is designed both to give officials more flexibility in ordering evacuations and give residents a better picture of their flooding risk.
"The new zones incorporate the best available data and will help the city to more effectively communicate to those most at risk depending on the characteristics of a particular storm," Deputy Mayor Cas Holloway said in a statement.
There have been only two mandatory evacuation orders in the city's history: for Sandy and 2011's Irene.
Despite televised urgings from Mayor Michael Bloomberg, text message alerts and police cars spreading the word with bullhorns in some neighborhoods, nearly two-thirds of residents stayed put after being ordered to leave for Sandy, according to a city-commissioned survey of 509 residents.
The storm ultimately killed more than 40 people in the city, almost all of them in areas under evacuation orders. The Oct. 29 storm also inundated some areas where residents hadn't been ordered to leave.
The new zones reflect a new understanding of flooding hazards from updated weather models and topographic data, and they assume that storm surge will coincide with high tide.
None lines up exactly with any of the prior three zones. But taken together, the new zones extend farther inland into some places, including lower Manhattan, parts of Brooklyn and the southeastern Bronx.
Also, some areas shift from a lower-risk designation into the zone most likely to be evacuated, although it doesn't include all the neighborhoods formerly in the highest-risk zone. A few are now in the next-highest zone.