On Monday, the Federal Emergency Management Agency's new flood maps for New London County will take effect.

For businesses and homeowners near the shoreline or inland waterways, the new maps could mean changes in the level of flood risk assigned to their properties. Some will see higher flood insurance rates as a result, said Diane Ifkovic, environmental analyst with the state Department of Energy and Environmental Protection and the state's national flood insurance coordinator.

"Some rates could rise up to 25 percent," said Ifkovic, adding that the changes are the result of the 2012 federal Flood Insurance Reform Act, as well as improved mapping technology used on the updated maps. The new maps replace versions that are about 20 years old.

On Thursday, the public will have a chance to see the maps and ask FEMA and DEEP officials questions. A short presentation on the new maps will begin the program, to be held at DEEP Marine Headquarters in Old Lyme.

"This is the time to find out about the maps, when the experts will be there," said Joe Sastre, emergency management director for Groton.

The maps are also available for viewing at town halls and can be found at www.msc.fema.gov.

Kerry Bogdan, senior engineer with FEMA Region 1, said the agency has been updating maps for the entire East Coast. Some changes are subtle, such as the flood-zone boundary moving a bit in one direction or another, while other areas have changed "drastically," she said.

Generalizing about how the maps have changed from the previous version is difficult, because the differences are unique to each parcel of property. That's why it's best for individual property owners to view the maps themselves and learn what the changes might mean for them, Bogdan said. "It's site-specific," she added.

The new maps offer a more accurate reflection of how wave action can cause flooding during storms, and the contours of some flood plain areas are larger, Bogdan said.

Ifkovic said some property owners who were just outside the flood zone may find that they are now within the zone and will be required to carry insurance. Others will find they are in a higher-level flood-risk zone.

Sastre said that for the town of Groton, there were "no surprises" in the new maps, and that they more accurately reflect where flooding actually has been occurring during major storms than the previous version.

j.benson@theday.com

IF YOU GO

Who: Department of Energy and Environmental Protection

What: Information session about new flood maps

When: 5 to 8 p.m. Thursday

Where: DEEP Marine Headquarters, 333 Ferry Road, Old Lyme

More information: www.msc.fema.gov