Climate change is causing more intense storms in Boston's suburbs, scientists say. That means more storm water is expected to flow over local streets in the coming years, picking up more oil, salt, and lawn fertilizer as it travels and dumping more of those pollutants in local lakes and streams.
To handle the predicted deluges, scientists at a recent regional conference in Maynard recommend following the example of officials in Littleton: Plant perennials.
For years, Littleton officials would close the public beach at Long Lake a few times each summer because of public health concerns over pollution from storm-water runoff. The town could have installed miles of pipe and built pumping stations and a treatment plant to keep the lake clean, but that would have cost millions.
Instead, using $630,000 in state grants and other funding, they built rain gardens - small patches of perennials planted on top of fresh soil and trap rock, created 1.5 acres of new wetlands, laid down porous pavement and sculpted "swales," or small depressions in the land, that direct storm water underground, rather than into the lake.
Since 2002, when the work was completed, the beach hasn't been closed once.
"Let the natural contours take care of the water flow," said Savas Danos, who oversaw the Long Lake cleanup as general manager of the Littleton Electric Light & Water Departments. "You get more ground water, sediments are stopped, and nutrients that cause algae blooms are taken up by the plants. It's flood control."
Danos spoke earlier this month at the annual conference of the SuAsCo Watershed Community Council, a nonprofit that advocates for the health of the Sudbury, Assabet, and Concord rivers and surrounding areas. At the conference, experts said measures like Littleton's rain gardens are likely to become more common.
Between 1948 and 2006, precipitation in Massachusetts and New Hampshire increased by 120 percent, said Iulia Barbu, a conference speaker and research assistant at the University of New Hampshire Stormwater Center, which was created in 2004 to test ways to mitigate heavy rainfall.
"Climate change is intensifying," said Barbu. "We have great potential for flooding."
Glenn Hodgkins, a hydrologist with the US Geological Survey who spoke at the conference, said local rivers have been swelling earlier and with more intensity in recent years in part because of the increased precipitation. He believes the region's flood-control infrastructure will have to be expanded.
"Peak flows seem to be up in New England," said Hodgkins. "If peak flows are up, you'll need to be able to handle more water."
Federal and state officials have already taken steps to manage storm water in Massachusetts. Last month, the EPA proposed new rules in the Charles River watershed that compel landowners with 2 or more acres of parking lots and other impervious surfaces to reduce their storm-water runoff.
At the same time, the state Department of Environmental Protection instituted a similar rule statewide that applies to landowners with 5 or more acres, though inside the Charles River watershed the DEP also adopted the 2-acre rule.
"Storm water is the single largest cause of pollution today in the Commonwealth," said DEP Commissioner Laurie Burt at the conference.
Landowners have 10 years to comply with the state regulations. EPA officials are currently testing their proposed rules with a pilot program in Bellingham, Franklin, and Milford. It is unclear when they might expand the rules to all 35 communities in the watershed.
The Sudbury, Assabet, and Concord rivers' watershed is especially vulnerable to pollution because development is quickly gobbling up the wilderness and open space that filters storm water flowing through the area, said Martin Pillsbury, manager of regional planning at the Metropolitan Area Planning Council.
In 1999, the last time studies were conducted, the three rivers' watershed had 23,150 acres of impervious surface, or 12 percent of the watershed's area in total. In 1971, when the previous study was conducted, only 17,100 acres were covered.
"Clearly, growth and development over the last three decades of the 20th century resulted in a significant increase in impervious coverage," said Pillsbury.
Another hydrologist at the conference, Scott Horsley of the Horsley Witten Group, said his business has grown as new water controls are slated to become either mandatory, as in the Charles River watershed, or popular, as in Littleton. His clients are discovering that rain gardens and swales are inexpensive but can be as effective at managing water as drains and culverts, which now require sophisticated equipment to conform to clean water standards, he said.
Horsley helps clients build rooftops with vegetation to capture rain water, porous parking lots with mesh concrete pavement that allow rain water to percolate downward, and other tools. Many of the measures are simple to undertake, he said, but they often aren't required by local regulations, so many builders don't bother with them.
In fact, zoning regulations often require developers to build in ways that manage storm water poorly, Horsley said. Wide roads are often designed so that large fire engines have room to maneuver on them, for example, but they also create more impervious surfaces that speed water elsewhere rather than retaining the rain and recharging ground water.
"We're probably making roads wider than they need to be," said Horsley. "The only reason we're building those roads is because the local codes say that's the way they should be. The developers don't like them. The people don't like them."
Kevin Maguire, a developer who recently completed 89 Oxbow, a 16-unit housing development in Wayland, said the town's fire chief waived the requirement for a cul-de-sac to allow fire trucks to turn around. That allowed Maguire to increase the density of the community and preserve more grassy surfaces to absorb rainfall.
Eighty-nine Oxbow was a Chapter 40B project, meaning it was proposed under state rules that allow developers to bypass local zoning as long as one-quarter of the development is sold at affordable prices. The developer still needs to negotiate with the town on site plans to gain permission to build, however. In the case of 89 Oxbow, town officials wanted a "green" development, which Maguire was happy to provide.
"I'm just trying to build really good housing for people," he said. "When it comes to green, it can be done."
Eighty-nine Oxbow has swales that keep water from running into the street, rain gardens that capture water, and rain barrels that store water to be used to water lawns. The development also has solar panels on its houses and other energy-saving features.
Most builders are open to smaller roads, rain gardens, and landscaping that controls flooding, said Jeff Rhuda, business development manager at Symes Associates, a Beverly-based commercial builder. In the end, he said, those measures are usually inexpensive compared with more traditional construction.
"You can either pipe the water, or you can build a nice swale on the side on the road and allow nature to do what nature does," said "Which do you think is much cheaper?"
John Dyer can be reached at email@example.com.