The hydrologist in charge of the National Weather Service’s Northeast River Forecast Center said it’s no accident that Cranston is seeing a remarkable increase in flooding and that more flooding and extreme storms will gradually become the norm.
“Smaller, urbanized watersheds are the types of places around the country that we have difficulty,” said National Weather Service hydrologist David Vallee. “You just don’t have any place to put the water. In a heavy rain event, it means your flood threat is increased.”
That was the grim assessment in a detailed presentation Vallee led in Cranston City Hall Tuesday night. In slides depicting the Northeast’s changing climate and storm characteristics along with historical and technical facts about the Pawtuxet River watershed, Vallee told members of the city’s Flood Committee and a group of about 30 residents affected by the historic floods of March 2010 that those floods are likely a taste of more to come.
Some of those property owners are hoping a federal buyout program eventually gives them the opportunity to walk away from their homes, some of which remain uninhabitable or unsellable. And they told Vallee and the committee that they worry every time it rains about centuries-old upstream dams failing or the Scituate Reservoir overflowing, causing the Pawtuxet River to flood and forcing them to relive the nightmare, or, in many cases, to make their ongoing nightmare even worse.
Vallee said a change in the character of the climate since 1980 has been driving a trend of shorter, compressed winters marked by the passage of fast-moving, rain-heavy storms that overwhelm drainage systems and cause local rivers to reach flood stage more frequently. Data shows warmer weather lasting later into autumn and arriving sooner in the spring. At the same time, average rainfall totals for the season — and per storm — have steadily increased. On top of all that is the increased development and urbanization of the lower watershed.
The twists and turns of the Pawtuxet River were formed by receding glaciers from the last ice age that left behind rich, fertile deposits of land. Neighborhoods were built on that land “because the river was a lifeblood with the textile industry,” Vallee said. More recently, “we put a shopping mall on it. In that basin, we’ve put in a whole lot of paved surface. We put in two interstates. We’ve got a ton of property and tax dollars and infrastructure sitting along that river.”
The remarkable 2010 floods were the result of three strong nor’easters that swept through Rhode Island and drenched the state with a total of about 15 inches of rain in just four weeks, Vallee said. And speculation that there was water mismanagement at the Scituate Reservoir or an upstream dam is unfounded, he said. “In actuality it had nothing to do with improper water management. It had nothing to do with snow melt.”
Meanwhile the ground was already saturated and had no capacity to absorb any of the rain that was falling. And being early March, there was no vegetation to draw some of that water out of the ground — one of the reasons the reservoir’s water level drops in the summer, in addition to increased water usage.
Before the third rainstorm, the ground was supersaturated and the Scituate Reservoir was already full. When the storm hit, the reservoir was dumping 31,000 gallons of water per second into the Pawtuxet, which eventually crested at about 20 feet. Some have suggested the reservoir could be drained in advance of major storms, but then you run the risk not having enough water in the summer when the levels tend to run low.
“The reservoir was never intended to be a flood control device,” Vallee said.
The north and south branches of the Pawtuxet River have two big dams. One, the Arctic Mill Dam, is at Factory Street. The other is in Natick. Both were built in the 1800s, some of which are beginning to break down.
“Some we don’t even know who owns them,” Vallee said. “It’s becoming an increasing concern year after year throughout New England. If they break, we run the risk of killing people.”
At the height of March 2010 floods, a dam failure is what “petrified” officials at the River Forecast Center.
“When we have these big rainfalls and we’re assuming this isn’t the end [of these types of storms,] we begin to run the risk of these 1800’s dams failing.”
Dams are expensive things to remove and dam removal includes a host of ecological concerns. A removed dam will alter the flow of water along the river and can release toxic chemicals trapped under generations of sediment that formed behind the dam walls.
And removing a dam is not a panacea. The dam at Pawtuxet Falls was removed earlier this year and has lowered the water level behind it somewhat. But the total amount of water flowing through the river has not decreased, nor will the area be any less susceptible to flooding with fewer dams.
“If we assume this rainfall trend is real and we assume that we’ll have a shorter snow season and more winter precipitation that is liquid, this is the new reality. These floods will not go away,” Vallee said. “My concern is these moderate floods, the ones that are really emotionally crushing for people to hear the rain pouring outside. I know the impact for folks living along that river is devastating.”
People living along the coast are facing the same thing with coastal erosion, “and it gets all the notoriety,” Vallee said.
The questions for people to ask are: can we protect? Can we adapt? Or do we retreat?
There is no question that the data shows an increase in total rainfall, rainfall amounts per storm and average temperatures since the 1980s, Vallee said. “Something’s a little iffy around here. I’m not going to blame it on global warming. What we’re not seeing is that it’s not snowing or we’re seeing more or less. We’re seeing bigger extremes. Some years you get nailed. Some years you get nothing.”
If the choice is to protect, Vallee said communities can consider things like flood walls, dams and dredging. But he urged all projects to be considered from a regional or basin perspective. Walls and dredging might lower water levels for Cranston, but it could make flooding downstream in West Warwick much worse.
If the choice is to adapt, there are some sacrifices. Some homeowners have moved their heating and utilities out of the basement or the first floor. Others have resigned to the fact their homes might be worth less than they owe, or paid, or are stuck paying for flood insurance programs.
The last option, which many homeowners hope to choose, is to retreat.
“It’s a hard decision and there are certain restrictions,” Vallee said. “It’s not an easy decision for us damn Yankees.”
And it’s a lengthy process.
Maureen Casey, a Perkins Avenue resident, said she and many others are frustrated with the response after the floods. The Army Corps of Engineers should look at the whole system from top to bottom, “to exhaust everything that can be done to contain [flood waters].”
That process was supposed to happen but “we haven’t heard anything, we haven’t heard where anything stands,” Casey said.
“We’re in tough shape and it’s going to take another disaster,” Casey said. If the Warwick Mall flooded again, its owners “are a lot more powerful than Maureen Casey on Perkins Ave. and then the state at that point would have to do something and do it rather quick.”
Matthew Lupino, a Fordson Ave. resident, said he and other residents living on the Pocasset River have their own issues and would like to see a flood gauge installed on that river.
Vallee said it costs about $12,000 to $15,000 for a flood gauge to be installed in a river.
Councilman Robert Pelletier said the March 2010 floods were an eye-opener and he learned a lot about how the soil’s limited capacity to absorb groundwater can cause neighborhoods to get washed out.
“It’s critical for us to understand the groundwater situation from a development perspective,” Pelletier said. “So future planners know and are aware they shouldn’t be developing in zones that are in danger of flooding.”