How Portland’s Bayside Plans to Cope With Increased Flooding Caused by Climate Change

Dec 15, 2016

Climate change poses a threat to property and infrastructure up and down the East Coast, and in Portland, residents and planners are starting to devise a response.

The latest installment of our occasional series “Beyond 350: Confronting Climate Change” focuses on the growing movement toward “coastal resilience.”

Portland’s Bayside neighborhood is one of the city’s most vulnerable to climate change. Rising sea-levels and more frequent, intense rainfalls are taxing its aging stormwater overflow systems.

“The biggest problem is that Bayside is our lowest elevation neighborhood,” says Bill Needelman, the city’s Waterfront Coordinator.

Needelman says this area, on a flat plain near the city’s Back Cove inlet, is 4-5 feet lower than bustling Commercial St. on the harbor.

“The construction of 295 in the 1960s essentially created a berm between the neighborhood and Back Cove. But it’s a permeable berm,” he says. “Water can come underneath the highway through the stormwater system at highest elevation tides, and when we have large storm events, rain is coming down the hill and through the sewer system. And a lot of water collects between the highway and the hill.”

You can see it at high tide on any given day — parts of the street that borders the cove, Marginal Way, are flooded shin-deep. Back in 2015, during a big, fast rain, the entire neighborhood flooded, with some cars set afloat.

And the science suggests it’s going to get worse. Cameron Wake is a climate scientist at the University of New Hampshire who has helped that state develop a plan for what’s known as coastal resilience. He spoke to several dozen Bayside residents this week about what their neighborhood faces.

“Essentially the rate of sea-level rise has doubled over the last 30 years. So the rate of sea-level rise is increasing,” he says, by more than a half-foot on the Portland waterfront over the last century, according to data collected by the National Oceanic and Atmospheric Administration.

And Wake says extreme precipitation events — four or more inches of rain over two days — are becoming more frequent.

“So you see back in the ’60s and ’70s and ’80s, average for Southern Maine we had two to three to four of these events. Over the course of the past two decades, right, we now have six and eight,” he says. “So a doubling of these events, and these are the big events, like the one that happened in 2015, that lead to big flooding.”

Credit Cameron Wake / University of New Hampshire

So what’s to be done? That’s the question city planners, Bayside residents, businesses and property owners are beginning to ask. A recent stormwater pipeline expansion project has been put on hold, clearing the field for big-vision thinking.

Wayne Feiden, a national expert in coastal resilience, says solutions range from retreat — moving buikldings and people away from the riskiest areas — to fortifying structures, to innovating new ways to adapt or revamping old ways. Something as simple as clearing a culvert.

He says there’s no one answer.

“You absolutely can’t retreat everywhere along the coast. You absolutely can’t armor everywhere along the coast, you can never armor in isolation without thinking about, ‘OK, if I armor here and the energy is going somewhere else, that’s going to make erosion somewhere worse,’” he says. “You need to think of these things as a system, but people are part of that system.”

Feiden says development pressure can play a role. When prime real estate is scarce, developers can be convinced to invest in resiliency projects on their own. Where pressure is less intense, governments may have to provide incentives, such as allowing taller buildings to compensate for the cost of taller footings needed to withstand high water events.

Credit Cameron Wake / University of New Hampshire

In Portland right now, developers are on the move, building new housing units at a fast clip. The Portland Housing Authority is one that’s planning for resilience as part of a 45-unit project, called Bayside Anchor.

Jay Waterman, the agency’s development director, says the building will include retention tanks under the site, and “rain gardens” — planted areas that allow runoff from walkways or parking lots to be absorbed by the earth.

“The new construction projects are probably only 5 percent of the land area in all of Bayside,” he says. “So it’s all those other existing buildings and existing impermeable surfaces like streets and parking lots that are the problem. They need to be raised up or permeable or infiltrating stormwater.”

Marginal Way in Portland on Thursday
Credit Fred Bever / Maine Public

Waterman suspects that many small projects — retention basins, rain gardens, sluiceways — will add up to an adaptive solution. There’s some grander thinking too: a giant hinged gate to close off the cove during tidal surges, or a levee system along its banks.

Laura Cannon, a Bayside resident and member of the neighborhood association, says the city’s public engagement process is important. But what’s also needed, she says, is for the neighborhood’s threats from climate change to be documented.

“How much of it is from the ocean, how much of it is from the river, how much of it is water that can’t move because old pipes are clogged with rust? How much water can we accommodate?” she says.

The city has set aside $100,000 to answer that question, with some of the funds to facilitate public participation in the Bayside Adapts initiative, and some for an engineering study to examine infrastructure gaps.