Boston’s flood zone grows, adding insurance costs for thousands

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BOSTON – New flood-zone maps put out by the Federal Emergency Management Agency expand the boundaries of parts of Boston at risk of being inundated and that may require thousands of property owners to buy flood insurance for the first time.

The new maps reassess the risk of flooding in coastal areas of Boston, Chelsea, Revere and Winthrop during the most severe storms, or those that are likely to occur only once in a century. According to Boston City Hall, more than 1,000 city acres with more than 9,300 residential units and over 2,400 businesses have been added to at-risk zones in the city alone. The maps become effective March 16.

Large parts of East Boston and Charlestown have been added to areas at risk. Increased harborside portions of the downtown and North End have also been added.

Some of the biggest changes can be found in the West End, which was barely touched by the 2009 boundaries. Another big addition was made in Dorchester, where the flood zone expanded inland.

A new mapping technique was used by FEMA, as the federal agency is often called, to improve accuracy, according to Dennis Pinkham, a spokesman. Aircraft flying over the region and measuring ground contours produced better topographical maps which were then combined with weather and tidal data to produce the new flood zone boundaries. The new maps don’t take into account the possibility of higher sea levels or other future risks.

The increase in accuracy may account for the bulk of the expansion, Pinkham said.  Boston property owners affected by the change can qualify for federally subsidized flood insurance through the National Flood Insurance Program since the city has adopted the FEMA maps to determine municipal flood zones.

The changes affect coastal properties, so property owners should be on the lookout for alterations that may affect them, according to Charlotte Moffat, the city’s flood plain manager.

The federal Flood Disaster Protection Act of 1973 and the National Flood Insurance Reform Act of 1994 require insurance for buildings located in a Special Flood Hazard Area on the currently effective Flood Insurance Rate Map. The city will give that designation to the new FEMA maps March 16.

Appeals contesting the new boundaries have been processed and adjustments to the maps have been made, Kerry Bogdan, a FEMA engineer, told WGBH News. The new maps will replace those created in 2009.

The state Conservation and Recreation Department, the city’s Environment Department and FEMA will host a community open house from 4 p.m. to 7 p.m. on Jan. 12 at the Boston Teachers Union Hall, 180 Mt. Vernon St. in Dorchester, to help residents and property owners understand the updated flood hazard zones.

A second meeting will be held from 5 p.m. to 8 p.m. in the cafeteria of the Staff Sgt. James J. Hill Elementary School, 51 Park Ave., Revere.

To learn more about FEMA’s updated flood hazard zones and FIRMS, visit: