🌊New Growth in Flood Zones

Goal C: A Climate-Resilient Region

Housing units built in 1% annual flood zones 2010-2020: 9,000

Commercial square feet built in 1% annual flood zones 2010-2020: 9 million

Part of what animates MetroCommon is the urgency of climate change and the need to prepare for more extreme weather events. More frequent and severe flooding, among other climate-associated threats, will pose serious risks for the region.

A basic step in reducing future property damage will be curtailing new construction – even resilient, restorative construction – in flood-prone areas and on sites that could be used for flood storage and green infrastructure. Today, however, in many vulnerable places, development is still permitted. It’s even often eligible for federally subsidized insurance and rebuilding in case of storm damage.

FEMA flood hazard areas are the most comprehensive available delineation of locations at risk of coastal and inland flooding. MAPC’s Massbuilds database indicates that in the 10 years since 2010, over 13,000 housing units and over 15 million square feet of commercial space were built in FEMA flood zones. This includes nearly 9,000 housing units and nearly nine million square feet of commercial square footage in areas with a one percent annual chance of flooding. This statistic also includes projects in regulatory floodways and areas with a 0.2 percent annual chance of flooding.

Included in the developments built in flood zones are some of the largest and highest-profile developments our region has seen over the past decade. Much of the Boston Seaport, redeveloped with high-density residential buildings and millions of square feet of commercial space, is in a flood zone, as are large developments in municipalities ranging from Cambridge (Alewife), Somerville (Assembly Row), and Chelsea (new regional FBI headquarters), to Lynnfield (Market Street at Lynnfield), Wellesley (Linden Square), and Stoughton (Woodbridge Crossing). While we haven’t analyzed the specific risk to any of these development areas, and some may include advanced resilience measures, their presence adds to the amount of property – and people, in residential buildings – at risk from climate change.

Future analysis using sea level rise projections will allow us to better understand how sea level rise will impact developments along the coast, but we know that as sea levels rise, projects in high-risk coastal areas will be more and more vulnerable to damage; and high-risk coastal areas will expand, encompassing more buildings and project sites.

Local officials can minimize future risk by discouraging flood-prone development using tools such as zoning to restrict development in current or future flood zones, and participation in the state’s Municipal Vulnerability Preparedness program. State permitting should be updated with standards that reflect projected climate conditions for the life of any project. Importantly, to have the clearest insight into where flooding is most likely, we must have access to accurate flooding data from FEMA and other sources, which provide transparent methods and limitations of their data.

MetroCommon Goals: Metro Boston is prepared for – and resilient to – the impacts of climate change, Goal C.4

MetroCommon Recommendations: Prepare for and respond to the threats of climate change, Action 1.3, 2.1, 2.2, 2.3, 3.1, 3.2, 3.3