About 1,100 Westport properties will be affected next year by new flood zone maps prepared by the Federal Emergency Management Agency, according to the town's Planning and Zoning Department.

Most of the affected properties are in neighborhoods adjacent to Long Island Sound or the Saugatuck River, according to P&Z Director Larry Bradley. Many owners of the properties affected by the reconfigured flood zones could face new flood insurance rates.

The new Westport flood zones, based on digital mapping, comprise part of a broader flood map revisions of coastal areas in Connecticut performed by FEMA during the last year, according to Bradley.

FEMA's latest round of flood zone changes is a more ambitious project compared to the last set of FEMA flood map changes in Westport, which only affected between 200 to 300 properties.

"Now they haven't only changed the unit of measure, but they've changed the measurement of the flood levels," Bradley said. "Before, you had to be 10 feet above the flood level. Now you have to be 11 feet above the flood level."

Town residents who are not planning to make major changes to their properties will not have to alter their homes to comply with the new flood maps. New residential construction, however, will have to meet FEMA's new standards.

"If you do any kind of construction on your home, you're going to have deal with the issue," Bradley said. "But if you're going to live in your house and not make any changes, you don't have to deal with it."

In the new maps, about 20 Westport properties have been added to 100-year flood zones, also known as Special Flood Hazard Areas, while about 40 properties have been taken out of those zones, according to the P&Z Department.

"I think those are more corrective issues," Bradley said of the change in properties included in 100-year flood zones. "I don't think those numbers really give any trend one way or another."

Between 2,500 and 3,000 residential and commercial properties in Westport -- about one-third of all properties in town -- are within 100-year flood zones, according to Bradley.

FEMA's new maps reflect a move by the agency to adopt more stringent flood zone regulations, Bradley noted.

"After Hurricane Katrina, they realized that a lot of those old models for flooding needed to be updated," he said. "They've gotten a lot more restrictive about what they want people to do in terms of elevating their buildings."

The new flood maps could also help town residents' preparations for another major flooding event, such as Tropical Storm Irene, which inundated much of Westport when it struck the Connecticut coast last August.

"If people's houses are more elevated, then there's less chance of damage," Bradley said.

The new flood maps are scheduled to be enforced by May 2013, according to the P&Z Department. Before then, property owners will be able to submit data to FEMA during a "public comment" period that runs until Sept. 6 if they want to contest flood map changes affecting their properties or to appeal the accuracy of the general mapping process.

A public hearing about the flood map changes will likely be held in Westport early next year, before the new maps take effect, Bradley added.

The average flood insurance policy costs about $600 per year, according to FEMA's National Flood Insurance Program website. Homeowner insurance policies usually do not cover flood damage, the website adds.

"Grandfathering" options are available from the National Flood Insurance Program for properties mapped into 100-year flood zones, according to the P&Z Department.

pschott@bcnnew.com; 203-255-4561, ext. 118; twitter.com/paulschott