New Boston building rules set standards for areas at risk of flooding

A man watches as waves crash into Fan Pier along the Seaport district in Boston, Mar. 3, 2018. An enormous nor'easter brought flooding, damaging winds, and even heavy snow to parts of New England.
A man watches as waves crash into Fan Pier along the Seaport District in Boston, March 3, 2018. An enormous nor'easter brought flooding, damaging winds, and even heavy snow to parts of New England. Keith Bedford/Globe Staff

The threat of coastal flooding remains one of climate change’s largest anticipated impacts on Boston.

But the problem has already more than loomed: In recent years, residents have experienced first hand floods that engulfed neighborhoods, particularly during one winter storm in 2018 that sent shock waves through the Seaport.

And climate models predict the problem will only intensify: By 2070, sea level rise is expected to hit 40 inches, according to the Boston Planning and Development Agency, which says buildings rising right now could still be standing come that time.

That said, the BPDA recently codified a new set of zoning requirements for new developments and retrofit projects, which officials hope will help better protect residents and their properties from the impacts of coastal storms and rising tides.

The BPDA Board voted to approve the Coastal Flood Resilience Zoning Overlay District last month. The district covers areas of Boston that are most at risk, including Downtown, the Seaport, the South End, Chinatown, East Boston, and waterfront areas of Charlestown and the North End, among other neighborhoods.

The Boston Zoning Commission voted to back the zoning overlay on Oct. 13, and Acting Mayor Kim Janey signed the standards into law on Tuesday.

“We must take the steps that will better protect our neighborhoods from the increasing threat of coastal storms and sea level rise,” Janey said in a statement last month. “By requiring developers to do more in vulnerable areas, we are protecting our infrastructure, our jobs, and our homes.”

The Coastal Flood Resilience Zoning Overlay District. —BPDA

The district includes areas beyond those outlined by the Federal Emergency Management Agency’s flood maps: The overlay covers areas of Boston that “could be inundated during a major coastal storm event … with 40-inches of sea level rise,” the BPDA says.

“For Boston to grow and thrive for generations to come, we must ensure that buildings constructed today are resilient and protected from the impacts of climate change,” BPDA Director Brian Golden said in a statement. “By updating our zoning code to go above and beyond the FEMA flood maps, Boston is leading the way in not only preparing for the storms of today, but the storms of tomorrow.”

The zoning overlay creates new standards and exceptions relating to building height and setbacks, along with lot coverage and required open space, among other criteria. The regulations largely apply to projects larger than 20,000 square feet, although they also apply to some beginning at 10,000 square feet in parts of the city closest to the harbor.

Buildings that undergo Resilience Review with the city will have their height measured from two feet above the “Sea Level Rise Base Flood Elevation” instead of at grade.

Only certain uses are allowed below the flood elevation, such as flood prevention measures, storage, and parking.

For setbacks, “projects will have allowances to extend into side yard, rear yard, and front yard setbacks for structures … such as stairs or ramps to get from surrounding grade to a higher first floor elevation,” the BPDA says.

The district would also allow side and rear yard structures to house utility systems in lieu of storing them in basements or below flood levels, according to the department. Those structures, along with stairs, ramps, and similar components, will be excluded from lot coverage and open space measurements, officials said.

“As we’ve learned the hard way over and over again in recent years, Boston sorely needs updated zoning — along with district-wide coastal solutions — to make sure that our most vulnerable citizens and more of our neighborhood buildings are prepared for sea-level rise, storm surges, and other impacts of climate change,” President and CEO of the nonprofit Boston Harbor Now Kathy Abbott said in a statement earlier this month. “We look forward to working with the City to implement these protections.”