MAPC graphic showing geocoded disaster assistance and flood insurance claims mapped with FEMA’s National Flood Hazard Layer

MA - Coastal flood maps leave homeowners in the lurch

Report recommends flood claim disclosures could help fill the gap

MASSACHUSETTS IS ONE of 15 states that has no flood disclosure requirements for a potential homebuyer, so residents usually turn to maps developed by the Federal Emergency Management Agency to see if their houses are vulnerable.

A new report from the Metropolitan Area Planning Council suggests those maps, which tend to focus on coastal and waterway flooding, may be missing a large part of the picture.

Fallout from a massive 2010 storm illustrates the problem. Across 19 days in March 2010, three storms dropped 1.5 feet of water on eastern Massachusetts, washing out MBTA tracks, flooding two dozen municipal buildings and 700 homes in Newton, leaving parts of downtown Peabody under seven feet of water, and causing other widespread flood damage in the Greater Boston region.

Using Federal Emergency Management Agency (FEMA) and the Massachusetts Emergency Management Agency disaster claims records, the MAPC report found that about 96 percent of flood damage claims after the historic downpour were in areas outside of special flood hazard areas identified on FEMA maps.

These maps are the “primary source of flood risk information” for homeowners and business owners, said Rachel Bowers, regional planning data analyst at MAPC. When massive flooding occurs outside of those zones, which are mostly focused on rising sea levels along the coast, inland homeowners can be in for painful shocks when basements unexpectedly flood after heavy rainfall.

“There is a lot of attention, as it justifiably should be, to climate change and seawater rise and its impact on the coast,” said Marc Draisen, executive director of the Metropolitan Area Planning Council, “but we also have to pay attention to inland areas – to flooding from rivers and streams, to flooding that may particularly affect previously filled land, to flooding in inadequately protected environmental justice communities, and to flooding of new development where perhaps adequate attention is not being paid to the possibility of stormwater now, 10 years from now, 30 years from now, certainly within the lifetime of those buildings.”

Researchers warn that downpours like those that occurred in the 2010 floods are going to become more frequent as the climate continues to change. The number of intense two-day storms increased by 74 percent from 1901 to 2016, the report says, and the heaviest rain events of the year now drop 55 percent more precipitation than the rainiest days of the midcentury.

The current FEMA maps roughly break down flood risk into 1 percent flood zones, 0.2 percent flood zones, and minimal risk flood zones, measuring the likelihood that a serious flood will occur each year. Only in the 1 percent flood zones are residents required to purchase flood insurance, but that category accounted for just 7 percent of all flood claims during the 2010 floods.

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