PORTLAND, Maine — Three years after it withdrew a set of high-tech maps showing flood hazards in Cumberland and York counties, the federal government has released new maps.

The Federal Emergency Management Agency released preliminary flood insurance rate maps, or FIRMs, for the two counties on Nov. 5.

The FIRMs could have a huge impact on property owners throughout the region because the maps are used to determine who is legally required to buy flood insurance — which can cost thousands of dollars a year — and where building development may be restricted because of flood potential.

In general, the new maps extend southern Maine’s flood zones inland, placing more properties in high-risk “special flood hazard areas.”

That’s a result of changes in geography and because FEMA is using more precise data and new methods for analyzing it, according to Kerry Bogdan, the FEMA senior engineer who oversees the mapping project in Maine.

For example, the mapping analysis, which takes into account factors such as topography, water depth and wind speed, now considers the impact of a flood’s largest waves. Previously, waves of average height were considered.

Despite the expansion of the flood zones, residents may find individual homes or businesses are now in zones with less flood risk than indicated by current FEMA maps, some of which are 30 years old.

So FEMA is urging the public to carefully review the highly-detailed maps found on the agency’s website and soon in town and city halls. There are more than 300 for Cumberland County alone.The agency also plans to discuss them at a series of public meetings to be scheduled in January.

“Because there have been changes, we really encourage people to take a look and understand what [the new maps] mean,” Bogdan said.

“If there’s a giant nor’easter coming at us, you want to be familiar with what your flood risks are sooner rather than later.”

Following the public meetings, there will be a 90-day period in which property owners and municipalities may comment on the maps or appeal their classifications. After any changes to the maps are made, FEMA expects them to be finalized by the summer of 2015.

The public review process is one with which southern Maine is already familiar.

In 2009, FEMA issued preliminary FIRMs that provoked protest from the public. In several communities, homeowners and business people complained about miscalculations in the mapping that placed their properties in higher-risk flood zones. Some people hired surveyors and experts who said the mapping analysis didn’t account for unique geographic features in southern Maine.

Portland appealed the 2009 maps because they placed the waterfront in a special flood hazard area, a classification that would have put an end to much development along Commercial Street.

Ultimately, FEMA discarded the 2009 FIRMs and went back to the drawing board.

The new maps incorporate feedback from the previous try, and should be “better overall,” said Joe Young, mapping coordinator for the Maine Floodplain Management Program, which works with FEMA.

But Young admitted that no map is perfect.

“The trouble with the maps is that they’re based on a modeled event. They’re done with a scientific approach, but they’re not a reflection of any one storm,” he said.

“So there’s always room in the model for mistakes. Especially when you have a coastline as complicated and irregular as Maine’s, it’s difficult to get things exactly right.”

With the maps released just two weeks ago, Young said it’s too early to gauge how communities will react. He said some may find they have fared better than they did three years ago, while others may find themselves in higher-risk categories.

“We may have settled down one hornet’s nest only to find we’ve kicked over another,” he said.

Jeff Levine, Portland’s director of planning and urban development, said the city will be paying close attention to see how the waterfront is classified under the new mapping. Areas such as Bayside and the islands will also be carefully scrutinized.

If necessary, the city may again appeal to FEMA to change the maps.

“[FEMA] was really responsive to us last time,” Levine said.

But like the public, city planners need to spend time carefully reviewing the maps.

“We’re just getting our teeth into them now,” he said.