Just across from one of my favorite writing spots, the window counter at Northampton Coffee on Pleasant Street, a mark is emblazoned on the former lumber building: “Flood Level – 1936.” When I walk past, the mark is almost a foot over my head.
After a morning’s writing, I often hop on my bicycle and cross the levee meant to guard the city from rising waters. As I cycle over it, I ponder the collapse of New Orleans’ levees during Hurricane Katrina and the overtopping of Louisiana’s levees in this August’s deadly floods. Wheels bumping, I roll down the dirt roads of the Meadows to pause on the bank of the Connecticut River and stare at its wide flat waters.
When I first moved to the Pioneer Valley, I used to wonder about the flood of 1936. That was 80 years ago this March. Shouldn’t we be due, I thought, for another nasty flood? And if downtown was inundated by at least 6 feet of water, why don’t we more often have floodwaters creeping into neighborhoods nearer the river?
It turns out downtown wasn’t flooded by the Connecticut River alone. The Mill River used to flow straight past Northampton’s center, powering its mills, and compounded the effects of flooding. After the destruction of 1936, the Mill was rerouted in a major engineering effort. Along the length of the Connecticut, new flood-control measures were put in place.
Not just Northampton, but all towns bordering the Connecticut River and its tributaries may soon find their past flood planning isn’t enough for a future governed by climate change.
In late October, Richard Palmer, director of the Northeast Climate Center at the University of Massachusetts, gave a packed audience at the Forbes Library his take on how the behavior of the Connecticut River will change as the climate warms.
His statistics were startling. In the last half century, the amount of water falling during the Northeast’s heaviest storms has increased 70 percent. Warmer air holds, and then dumps, more moisture.
All extreme events – both droughts and floods – are now more frequent both here and worldwide, said Palmer. Our severe drought in New England this past summer fits these observations.
How will rivers be affected? In winter, less snow and more rain will pour water into rivers in more sudden bursts. Palmer and his colleagues have projected that by 2075, towns like Chicopee and Deerfield will see winter stream flow increase by at least half and possibly as much as double.
“A large, unexpected flood of greater magnitude than we’ve seen in the past is what I’d be afraid of, because it would have large economic consequences,” Palmer said.
In spring and summer, meanwhile, water levels could drop by comparison to today. No longer reliably fed by snowmelt, spring flows could decrease by almost 15 percent.
Normally, floods are cyclical, meaning you can predict approximately how often a flood of a given size will occur. Urban planners typically set up infrastructure to protect against a 100-year flood, or a size of flood that tends to occur about every 100 years.
But as the world warms, these are no longer normal times. Today, said Palmer, “we can’t look to the past to predict the future.”
What used to be a 100-year flood, in other words, could become much more frequent, threatening the area every 50 years, or possibly more often. Millions of dollars in flood planning could become outdated or even obsolete. Our planning may soon protect us, if you’ll excuse a pun, only against run-of-the-mill floods.
Every fall, I walk my first-year students at Smith College down to the Mill River. They stare at the levee that rises up alongside the bank. They wade into the water to measure its width and speed.
They watch videos from 2011, when floodwaters from Tropical Storm Irene drowned Smith’s boat house. In Greenfield, the water knocked out the sewage treatment plant for two days and destroyed the Eunice Williams dam. Roads and mobile homes in Hawley were washed away.
Then the students use the history of water flow on the Mill since 1939 to calculate how often we expect floods of various size to occur. They discover that we should expect an Irene-sized event about once every 17 years.
But when they split the data set in half, everything changes. Using only earlier data up to 1978, the calculation gives an Irene-sized flood only every 25 years. But from 1978 to now, the same storm is expected every 12 years. In other words, recent decades should see twice as many Irene-sized storms compared to the past.
The students’ limited data set represents only a rough estimate, for just one spot on one river. But their simple classroom calculation exactly dovetails with what experts tell us to expect from a changing climate.
We often think of climate change as a confusing technical argument playing out among scientists and bureaucrats. But its effects are already there for anyone to see, even a college freshman barely out of high school.
The Connecticut River is the lifeblood of our region. It travels through four out of six New England states. Its sediments and waters carry and deposit nutrients, feeding farmlands and ecosystems. From the Algonquian Indians, who named it “Connecticut” meaning “long river,” to the pioneer industrialists who built their mills on the banks, the river and its tributaries created the region’s society and economy.
But like so much of the natural world, the river will support us only in the measure that we steward it as a resource, and understand it as a changing entity.
And as we give it our excesses, spilling greenhouse gases from our cars and power plants and industry into the atmosphere to fuel an ever-warming climate, excess is exactly what the river will give us in return.
Naila Moreira is a writer and poet who often focuses on science, nature and the environment. She teaches science writing at Smith College and is the writer in residence at Forbes Library in Northampton. She’s on Twitter@nailamoreira.