To Prevent Floods And Erosion, Let Vermont's Rivers Take Their Own Path
As many Vermonters know all too well, catastrophic floods have become increasingly frequent in the state. In many cases, they devastate homes, roads and farms.
In the last four decades alone Vermont has seen three disastrous floods that occurred at the regional or statewide scale – at or above the so-called 100-year flood level – including Tropical Storm Irene.
For decades the state has tried to protect roads and homes from floods and erosion by bringing in construction equipment and bolstering riverbanks with expensive rock walls.
But in recent years the state has been trying a new approach: creating river corridors to allow the river to carve out its natural, more meandering path. And that means letting the river flow, even if it erodes farmland or what was private property.
Stowe's river corridor
On a crisp sunny day, river scientist Mike Kline crunches through the brush alongside the Little River downstream of the village of Stowe.
Kline is the manager of the rivers program at the Department of Environmental Conservation. He points across the river to the first river corridor the state ever purchased.
It doesn’t look like much; it’s about 100 feet of pebbly beach, some shrubs and grass. But this newly established bank is a big achievement. The river corridor is one piece of a bigger plan: to allow the river to re-meander so it can slow down, keeping it from eroding away roads and homes.
And Kline says the plan is working. Slowly.
"Rivers are working year after year to get back to that natural geometry. The most important thing we can do is change our land-use expectation and move out of the way." — Mike Kline, Department of Environmental Conservation
“This juvenile floodplain over here is going to grow, eventually, as the river meanders,” Kline explains. “It’ll create, you can see upstream, a whole other gravel bar feature on this side of the river.”
The fact that a new floodplain can begin to form at all – instead of the river water being forced to shoot downstream in a straight channel — is thanks to a statewide river corridor program that began right here in Stowe.
It started when Kline, the Department of Environmental Conservation and the Stowe Land Trust worked with several willing landowners to buy back a stretch of their property alongside the river. With that land the group created the first river corridor easement.
Why riprap fails
The key was that landowners had to agree to give up their rights to farm or build structures on the land, and most importantly, give up the right to attempt to armor the river bank with rocks to hold the river back.
That’s because scientists and town managers alike realized that those expensive efforts to hold back the river by stonewalling its bank, called riprapping, ultimately fail over time. Stowe residents know this all too well, says Tom Jackman, the planning director for the town of Stowe; he’s seen the town spend extensively over the years, riprapping the river to keep it from eroding the town’s recreational bike path.
"Once you riprap a stretch of river ... you're pretty much committing to keep replacing that over years." - Tom Jackman, Stowe planning director
“Once you riprap a stretch of river,” Jackson explains, “once you armor it, you’re pretty much committing to keep replacing that over years. Ultimately, it fails at some point, particularly with a river like the West Branch, really powerful with high water events. It drains off of Mt. Mansfield and can go from a little trickle to a raging torrent. It’s a very active, flashy river.”
That’s exactly why the Mike Kline and the DEC decided to change tactics. Instead of trying to fix the river, they decided to try to fix the land use instead.
“The light bulbs went off and we thought, rivers are working year after year to get back to that natural geometry,” Kline says. “The most important thing we can do is change our land-use expectation and move out of the way.”
Un-straightening Vermont's rivers
In the eight years since the first easements went into place in Stowe, aerial photos show that the river is reclaiming the land, eroding some of the easement property and slowing down, and depositing sediment on opposite banks.
Restoring this meander is key because in Vermont most damage comes from erosion, not from high waters. Deep, fast-moving waters, forced down channelized rivers, augment this erosion.
Slowing down the water helps reduce flood risk because, as Kline explains, “slower water can absorb into the ground, instead of fire-hosing its way down into the valley.”
"Slower water can absorb into the ground, instead of fire-hosing its way down into the valley." - Mike Kline, Department of Environmental Conservation
But across much of Vermont, many rivers and streams are still structured like firehoses: deep, fast running channels that were originally carved out to power mills or float lumber down river. It’s a problem that affects nearly all corners of the state.
“If [we] talk about the surveyed rivers, one out of every three river miles in Vermont has been straightened,” Kline says. “That’s thousands of miles of rivers and streams, from our very smallest to largest.”
Kline says the river corridor program is a win-win: river corridors protect homes, roads and infrastructure, and they save money.
“It not only helps landowner divest of those riparian lands,” says Kline, “but it is much cheaper for taxpayer in long run.”
Cheaper to meander
Kline says for land that is actively eroding, landowners who want to riprap the riverbanks are looking at around $70,000 to $100,000 for a project, whereas for the state to buy an easement along that stretch might cost around $25,000 to $30,000.
“So [for] literally one-third the cost… rivers [are given] space forever, versus $100,000 of riprap with shelf life of 10 years, and [then] we’re right back in there armoring again.”
And lastly, Kline says putting the meandering bends back in the rivers protects the water quality of Lake Champlain.
About 21 percent of the phosphorous pollution in the lake comes from rivers. If river water is allowed to slow down and curve, it instead deposits most of its sediment along the riverbanks, in floodplains and wetlands where plants can use it to grow.
That’s because about 21 percent of the phosphorous pollution in the lake actually comes from rivers. But if the water is allowed to slow down and curve, it instead deposits most of its sediment along the riverbanks, in floodplains and wetlands where plants can use it to grow.
“If these places are protected, [it] can really make a difference,” says Heather Furman, the Vermont state director of the Nature Conservancy explains. “Not only for our rivers to be able to move within existing corridors, floodplains, but also for water quality.”
“[River corridors] can serve the purpose of absorbing sediments, pollutants from rivers before they hit the lake,” Furman added.
A strengthening current
So far the state has signed about 52 river corridor easements. And more than 30 towns, including Stowe, have also adopted regulations to limit future development in erosion zones along the river.
While the DEC rivers program was working on these new approaches before Tropical Storm Irene, Kline says the damages further spurred the Legislature to act.
"If these places are protected, [it] can really make a difference. Not only for our rivers to be able to move within existing corridors, floodplains, but also for water quality." — Heather Furman, Nature Conservancy
Caitrin Maloney with the Stowe Land Trust agrees: “If [you] can take a bright spot from a disaster, that was one of them,” Maloney says. “Okay, now we can organize around this, and say this is a priority. And [Irene] is what happens when we don’t.”
Vermont’s new Clean Water Act does strive to make it a priority. The state is looking to expand the river corridor program to address more of the thousands of conflict areas across the state, where channelized rivers threatened homes and infrastructure. The hope is that over time this will give the rivers space to restore to that natural, dynamic balance.