Flood-prone watershed is focus of nearly $1M project
Scene of some of the worst of the floods of 2010, Canonchet Road in Hopkinton, R.I., leads past farms, homes, a small church, a plastics factory and a hodgepodge of man-made structures meant to control the flow of water.
On a late June morning, after inspecting the shallow earthen dam that blocks Canonchet Brook to form Ashville Pond, Maren Frisell and her team stopped at a concrete culvert built to let a small stream flow under the road.
Someone had placed a wire basket around the culvert opening on one end to keep the pipe from clogging with leaves, sticks and other debris.
After water resources engineer Rachael Weiter waded into the water with a flashlight, it was clear the wire basket was only marginally effective. Behind the culvert, water ponded into a small swamp. Dragonflies soared over the cattails. Bullfrogs gulped.
Across the road, a trickle of water gurgled out of the culvert toward a curious kind of concrete funnel that constricted the unnamed stream to two small openings.
“It’s an interesting structure — a double weir,” said Frisell, who also is a water resources engineer. “I don’t know why anyone would put that structure here. It just causes backflow issues.”
Since early June, Frisell, Weiter and intern Zach Valerio have been poking around culverts, dams and bridges throughout the 300-square-mile watershed of the Wood and Pawcatuck rivers to assess how these structures intended to manage water for the human environment may instead be making roads, homes and businesses more prone to flooding.
The three are doing the field work component of a flood resiliency project headed by the engineering firm Fuss & O’Neill.
In all, 550 structures in the watershed's 14 towns will be measured and inspected by the end of the summer, including some in the Connecticut towns of Stonington, North Stonington, Voluntown and Sterling.
“The whole goal is to make recommendations to reduce the flood hazard,” Frisell said.
While damage from the 2010 floods occurred throughout the watershed, it was particularly intense in the most developed areas along the lower Pawcatuck River, along the border between Connecticut and Rhode Island, where all the water from the smaller tributaries converges.
For people in the section from the Potter Hill Dam in Westerly to the Route 1 bridge between Pawcatuck and Westerly, becoming less vulnerable the next time the river swells over its banks is simply prudent action in a community aware that its central natural feature both gives and takes.
The flooding in the spring of 2010 caused about $42.4 million in damage in Washington County, R.I., and New London County, mainly in the sections in the Wood-Pawcatuck watershed, according to the Federal Emergency Management Agency.
A 2012 U.S. Army Corps of Engineers report concluded that a watershed-wide project to reduce flood risk is warranted.
“The river is a wonderful resource, but we should be mindful that there have been significant floods,” said Joe Miceli, owner of Miceli’s Furniture, the downtown Westerly business started by his father in 1952. “The town anticipates there will another significant flood.”
In 2010, the warehouse for Miceli's furniture store was among the Canal Street businesses under water. Now, after accepting the town’s offer to buy his warehouse, he’s looking for a building on higher ground to replace it.
Westerly Town Planner Marilyn Shellman said three homes and two businesses in the flood-prone area have accepted buyout offers from the town, while two others have burned down.
Some of the buildings have been razed, creating vacant land along the river’s floodplain that will be able to hold floodwaters.
The town would like to purchase other Canal Street buildings in harm’s way, but it hasn’t been able to get the owners to agree.
“We have properties at risk,” she said, “but for some people, it’s out of sight, out of mind.”
Now, however, the flood resiliency project is bringing the potential for future floods back to the attention of the region.
Using a $720,000 federal grant plus $200,000 in local matching funds, the Wood-Pawcatuck Watershed Association this year hired Fuss & O’Neill to undertake the project, the first to take on flooding issues on a regional scale.
“This project will help out the human-built environment and also the natural environment,” Denise Poyer, program director of the watershed association, told a group newly convened at the association offices March 26.
They were representatives of the 14 watershed towns, along with Connecticut, Rhode Island and federal land-use and emergency management officials comprising the project's steering committee.
Never before, Poyer said, has a gathering representing this particular geographic configuration — coming from all parts of the watershed around a common purpose — been organized.
“It’s the first time all the towns in the watershed have gotten together to specifically look at flooding issues,” she said. “Doing things town by town, you don’t get a lot done. You need to put this together in a cohesive format.”
Erik Mas, vice president of Fuss & O’Neill, said the recommendations that will be developed from the field work aren’t going to eliminate all flood risk.
“But they will minimize and reduce the damages, and help the area recover more quickly, especially from routine, smaller events,” he said.
Compared to similar projects his firm has completed, he said, this one is relatively large, encompassing 480 miles of rivers and streams, portions of two states, and 70 dams of various sizes, designs and histories, along with hundreds of smaller structures.
His agency will present findings to municipal officials and provide training about how to carry out a flood management plan and recommendations. There also will be presentations to the public this winter and next spring.
One of the main challenges of the watershed, he said, is the way development has occurred.
While it is about 75 percent forested, a condition that usually means there are ample open lands to absorb floodwaters, much of the development has occurred in the most vulnerable areas — the floodplains adjacent to the riverbanks — and in some cases, encroaching on natural stream channels.
The development is also highly concentrated in the lower part of the watershed, he added.
"The focus here will be on strengthening natural ecosystems, using natural approaches to enhance flood resilience," he told the steering committee. "This watershed is one of the gems in terms of biological diversity and surface water quality, and it's one of the last and largest intact forested areas between New York and Boston."
Instead of reducing flood risk by re-engineering nature, he said, the aim of the project is to work with natural systems.
Recommendations will identify wetlands that have been degraded that should be restored to hold more flood waters and provide better wildlife habitat.
Flood plains and other vulnerable areas where no development should occur will be identified.
Towns would be advised to amend land-use regulations to favor development that absorbs storm water with swales, pavement that allows water to penetrate and other types of "green" infrastructure, he said.
"We'll recommend green storm water technology to put more water back into the ground," he said. "There will be opportunities for retrofits and low-impact green infrastructure for new development."
Obsolete dams will be targeted for removal, and others tagged for repairs or upgrading for better storage of floodwaters. Culverts that are undersized and clogged will be identified, with suggestions for cleaning and replacements.
"We're definitely going to find a number of undersized culverts that are contributing to flooding," he said.
A priority for the recommendations will be established so officials will know which ones will have the greatest benefits, he said, adding that working on a watershed-wide scale will be more valuable for all the towns involved, lessening the chances that one town will attempt to reduce its flood risk by inadvertently sending the water to a neighbor.
"It's more efficient to work together, and it increases the chances for grant funding if multiple towns are involved," he said.
Editor's note: This is the fourth in a five-part series.
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