The federal government is redrawing its maps that define flood zones, a move that could have a significant impact on the cost of flood insurance for homeowners and businesses.

This summer, the Federal Emergency Management Agency redrew flood maps for New London County using new topography data and updated computer models on how flooding occurs. For some people, the new maps could change whether their property lies on the official flood plain.

"Probably the most important thing, for anybody regardless of where you live, is just to check," said Diane Ifkovic, the state's flood plain manager. "Go to your town hall or, if it's online, check the preliminary maps. Do it just to see if anything has changed, if you're being taken into the flood plain, taken out of the flood plain. Just so you know."

The new maps are available for review at local town or city halls, Ifkovic said. Many towns have posted the new maps to their Web sites.

Some communities, including Stonington and Groton, have held meetings to educate residents about what the changes to FEMA's flood maps mean to property owners, especially those whose homes are being placed on a flood plain for the first time.

"We've been fielding people's questions all month, and many people's classifications are changing just slightly," said Michael Murphy, Groton's director of planning, at a community meeting about the map changes held in late November. "The principal reason for this meeting ... is to talk to people who were not on the flood plain before and are now being included on the flood plain."

Standard insurance policies typically do not include flood coverage, but most banks require mortgage-holders who live on a flood plain to carry flood insurance through the federal government.

The most significant impact of the new maps will be on people who live in areas that are now being considered flood plains for the first time. There is an appeals process, but "it's more than just 'I don't like that you say I live on a flood plain now,'" Ifkovic said.

Anyone who wants to submit an appeal must file one with paperwork on the FEMA Web site, www.fema.gov. The appeals process requires a property holder to hire an engineer who can show that FEMA's data is inaccurate or flawed, Ifkovic said.

A grandfathering clause allows property owners whose flood risk is increased to save money on their insurance, Ifkovic said. If property owners purchase a policy before the new maps are officially released, tentatively scheduled for Sept. 30, 2010, their first year's bill will be based on their current flood zone.

The policy's cost will increase the next year to a "standard policy," but it will not be as high as it would be without the grandfathering clause, Ifkovic said.

"This way they can have a policy for $1,200 when they could have had a bill for $2,200," Ifkovic said.