Coastal flood maps leave homeowners in the lurch

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.

With the FEMA maps capturing so few of the flood claims, MAPC researchers dove into contributing factors, like distance from bodies of water or wetlands, the year a structure was built, the type of soil in the area, or the slope of the ground beneath the structure. Buildings constructed between 1940 and 1980 were disproportionately impacted by the flooding, likely because they were built closer to waterways and wetlands than later houses, as were those on flatter ground.

Disaster claims paid to Massachusetts residents after the storm totaled $59 million, with awards capped at $29,900 and the average amount awarded per claim $1,762. Average flood insurance payouts dwarfed the disaster claims, at $10,526 per claim, and the highest flood insurance payment was $500,000, said Anne Herbst, one of the report’s primary authors. 

This suggests, Herbst said, that there may have been many homes with serious flood damage that simply were not insured. So the $59 million in damage likely significantly undervalues the overall costs to homeowners.

In the most affected municipalities, like Randolph, Sharon, and North Reading, about 6 percent of all homes filed flood claims. For a municipality to see that many homes with serious flood damage is “a fairly remarkable number, especially if you consider that this only counts residents who pursued the process of filing a claim,” Herbst said. In some census blocks, more than one in ten homes filed claims.

MAPC authors interviewed homeowners about the 2010 flood, and two-thirds of them reported recent flooding. The long-term angst associated with dealing with flooded basements and maintenance is profound, researchers said.

“There is an undercurrent of general stress,” one anonymized interviewee said. “It puts us in a bad position future-wise. We want to be here, to put down roots. Now we’re in a property we’re not even sure what to do with. Should we invest? Should we sell? We wouldn’t want to surprise the next family.”

MAPC recommends several actions to reduce uncertainty for homeowners in inland flood-prone areas, primarily by increasing access to flood claim data and requiring flood history disclosure. Researchers are also calling on the state to provide more funding for stormwater management to repair aging infrastructure and add new infrastructure.

Dedham’s town engineer, Jason Mammone, said the town has used state funding grants to gather data and convene groups of residents to offer input into short- and long-term resilience goals.

“Even some of the short-term goals, even though they don’t seem huge in the grand scheme of things, it’s something tangible that people can grab onto,” he said. The town expects to go back to residents this month with goals that they hope to advance if they get another grant through the state Municipal Vulnerability Preparedness program.

A statewide climate change assessment came out in December and the state is updating its hazard response plan, said Mia Mansfield, director of climate adaptation and resilience at the Massachusetts Executive Office of Energy and Environmental Affairs.

Within the climate assessment, damage to inland buildings was the top infrastructure sector issue identified, Mansfield said, because of “the magnitude of the impact, the disproportionality of the exposure.”