Flooding in Levittown left one car soaked. (July 10, 2010)

Flooding in Levittown left one car soaked. (July 10, 2010) Credit: Newsday

FEMA's controversial Nassau County flood map is accurate, the agency said Wednesday, so no property owners will be removed from it - or from the requirement to spend as much as $3,000 a year for flood insurance.

The Federal Emergency Management Agency said its ground-survey spot-checks last year of elevations of 100 coastal Nassau locations verified a 2009 map's accuracy. Consequently, the 25,000 properties that the map added to the flood zone will remain, it said.

The decision also means homeowners who were required to buy flood insurance by their mortgage banks now will have to keep the coverage, which can cost as much as $3,000 a year.

But the results will not end the controversy over the map. Questions remain about FEMA's use of a model from an unpublished U.S. Army Corps of Engineers study of stormwater heights from Fire Island to Montauk to develop the Nassau map, officials and residents said.

FEMA promised to do the spot checks at a contentious meeting last year in Valley Stream. "The report confirms what we said all along, which is that we believe the Nassau County data was valid and the science was good so there would be slight changes in the elevations and it would not impact the flood zone or take anyone out of it," said Timothy Crowley, FEMA regional director of mitigation.

Crowley said the majority of survey points checked last year showed lower elevations than the county data used in putting together the map, meaning the flood zone could have been even bigger had the information been available two years ago. Some of the heights measured from the ground did show that aerial survey information supplied by Nassau for the 2009 map were higher by as much as 1.4 feet. But that was within FEMA's standards for accuracy.

Even those locations that were higher were not high enough to remove them from the flood zone because the level of expected flooding - the "base flood elevation" - was still higher than the revised ground elevation at the site, Crowley said.

"I'm disappointed but not surprised," said Carol Crupi, a Valley Stream civic leader who has been fighting the map. She said the spot checks were "an effort in futility" because FEMA hasn't changed the base flood elevation predictions.

To date, 105 Nassau residents have successfully appealed their inclusion in the flood zone and have been removed.

Sen. Charles Schumer (D-N.Y.), who has been fighting FEMA over the map, said, "FEMA's decision to raise base flood elevations was predicated on questionable data and flies in the face of decades worth of local data." He plans to reintroduce legislation that passed in the House but not the Senate last year to mandate a five-year moratorium on banks requiring flood insurance for homes in flood zones until questions about map methodology are resolved.

Jay Tanski, coastal processes researcher for the New York Sea Grant Extension Program, said he didn't expect any big changes from the ground elevation data spot-checks. "The bigger thing is the [Army Corps] model. They really have to . . . make sure that the model is working correctly."

Crowley said FEMA is conducting a flood study for New York City and Jamaica Bay, and results could affect the flood predictions for Nassau when it is completed by year's end.

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