The Federal Emergency Management Agency has released long-awaited revisions to its flood risk maps.

FEMA released the updated flood work maps for Atlantic, Hudson, Monmouth and Ocean counties Sunday evening. Homeowners can check their addresses on a FEMA website to see how the agency classifies their flood risk.

FEMA says the new maps decrease the number of homes in high-risk "velocity" zones from advisory maps that the agency released in December, which showed the risk of flooding was worse than believed. Those maps overestimated the amount of land in the V zones, officials said today.

Properties in the high-risk zone would have to be raised or risk higher flood-insurance premiums, and some residents and legislators worried that it would be too costly for some homeowners to comply.

In Atlantic County, there was an 80-percent decrease in the number of acres labeled as V zones, Bill McDonnell, the mitigation branch director for the FEMA region that includes New Jersey, said at a briefing this morning about the new maps. The county has a significant amount of marshland that could absorb a wave's impact, he said.

There was a 76-percent decline in V zone acres in Hudson County. Ocean County had a 45-percent decrease in V zone acreage and Monmouth had a 46-percent drop in V zone acres, McDonnell said.

"We did not take into consideration all of the impediments or obstructions that would impede a wave" in the earlier maps, McDonnell said. In Hudson county, a number of urban structures would obstruct waves, officials said.

Authorities said they didn't have the precise number of homes affected by the changes.

The maps will give Superstorm Sandy victims deciding whether to rebuild more information about what to do. State and federal officials have said that residents won't get grants to repair homes damaged by Sandy unless the homeowners comply with the new maps.

Officials also stressed that the revised maps still reflect an increased risk for flooding.

"The overall risk has increased from the current effective map," McDonnell said. "We anticipate that the risk may increase in the future."

New Jersey Sen. Robert Menendez praised the map revisions in a statement last week, saying the earlier versions were "fundamentally flawed."

Maps for Salem and Cumberland counties are expected to be released shortly, followed by Middlesex, Essex, Union and Cape May.

Any changes to insurance rates wouldn't go into effect until 2014, after flood insurance rate maps are released and the public and local officials have the chance to provide feedback.

Contact Emily Babay at 215-854-2153 or Follow @emilybabay on Twitter.
Contact the Breaking News Desk at 215-854-2443; Follow @phillynews on Twitter.