Nowhere to Runoff: Somerville’s Flooding Problem

floodingUnion Square in 2010. Photo by Brandon Constant.

Suzahne Riendeau had owned her home on Cedar Street for about two years when she experienced her first bad flood in 1998.

“The closer I got to the house, the deeper the water got, until finally I got to my house. The water was about mid-thigh,” she recalls.

Further down the street, the water had nearly submerged some of the cars that had been parked there. Only one step was visible on the porch of Riendeau’s house. When she finally got inside, all she could see from the top of her basement stairs was water and whatever was floating in it—including her washer and dryer.

“I lost everything,” she says. She estimates it’s cost her around $50,000 to replace all the items waterlogged during bad flooding over the last two decades—which is why she gets nervous every time it rains.

Riendeau is one of many residents who have paid the price for Somerville’s flooding problem. Despite the fact that most of Somerville seems to be on higher ground—including Riendeau’s house on Cedar Street—a perfect storm of factors makes many parts of the city susceptible to flooding. Silt and clay-heavy soil makes absorbing rainwater a slow game, and much of Somerville’s land is covered by impermeable surfaces like pavement or buildings. Spring Hill is very close to the water table, and until it was so polluted that it was filled in during the 1920s, Millers River ran right through Union Square.

As far as natural disasters go, flooding is considered by the city to be the greatest potential hazard to people and property. In the latest draft of Somerville’s Hazard Mitigation Plan, the city identified 989 buildings on 6.37 percent of the city’s land where flooding most frequently occurs. At the time of the plan’s draft, the estimated value of those buildings amounted to $385 million in 2013. According to that plan, which was prepared by the Metropolitan Area Planning Council, at least 16 “natural hazards” have been designated “disasters” at the state or federal level since 1990, the vast majority of which involved flooding. As the climate changes, and with future development promising more impermeable surfaces, the problem can only get worse.

“I think what’s happened in the last generation or so is that even more surface [has been] covered over by concrete,” says Ward 5 Alderman Mark Niedergang, citing the combination of increased development and lax regulations as a factor. It wasn’t until 2012 that the Board of Alderman introduced ordinances that required a minimum amount of permeable surfaces for properties. Before then, some property owners could pave over their lawns for more parking or to avoid lawn maintenance, sans permit. According to a 2011 land use report, 77 percent of Somerville’s land is impervious.

flooding paved

A paved lawn in Somerville. Photo by Jen Stevenson.

Part of the problem could be alleviated by low-impact development (LID), says Jennifer Stevenson. She’s been studying Somerville’s impervious pavement problem for her capstone project at the Boston Architectural College. Stevenson has lived in Union Square for five years and lost her car to a flood. She believes that, if implemented correctly, LID projects could make a huge difference with minimal investment.

“If you think about big infrastructure, it’s one massive project, and it’s basically underground. We pump [the water] off site for it to be treated. LID is decentralized,” she says. “If you have enough LID projects, you end up connecting them and having an impact.”

When it rains in Somerville, the water slides off roofs and over pavement and then is either absorbed into the ground or diverted into a storm drain. With few areas to soak up the water, most of it is directed to the drains, where it overloads the aging, antiquated infrastructure. The water then backs up and out of the drains. LID solutions could help ease that pressure. Planting more trees, using pervious pavement and introducing green roofs—which are covered in vegetation—are all ways that Somerville could become more absorbent.

LID isn’t a one-size-fits-all solution, Stevenson says. Each project must be site-specific in order to avoid causing more harm than good. In 2009, during the renovation of Albion Park, the Department of Public works used perforated pipes to try and let some rainwater seep into the soil instead of whisking it all away. Surrounding houses soon had flooded basements, and the pipes had to be replaced.

One blanket solution that Stevenson suggests is reducing the water flowing from our houses to the drains. For instance, low-flow showerheads and toilets could cut back on how much water residents are sending to the sewer. And that matters: Stormwater and sewage meet in Somerville’s single-pipe system, which means when Riendeau’s Cedar Street basement floods, the water is fecal.

Overhauling the infrastructure is estimated to cost somewhere around $5 billion, money that Somerville doesn’t have. A few improvement projects are underway—plans for the Cedar Street Flood Mitigation Project are in the works, for example—but Niedergang says that the city needs to act quickly to capture some of the development gravy in order to fund a better infrastructure.

“We have the opportunity to get funding from developers for this. These folks are going to be coming in here, and they’ll be building stuff that people will use and enjoy, but they’ll also be making a ton of money. And so they need to do their fair share to help us out with this problem,” he says.

“We need that money. We don’t have $5 billion to redo the sewer system. If this doesn’t get planned out and prepared for, all of a sudden you’re up a creek without a paddle.”