Deploying beavers to create dams could prevent Ellicott City flooding
Pickering is an ancient village in the Ryedale district of North Yorkshire, England, U.K. Descriptions of the place bring to mind Ellicott City, the old mill town in Howard County, Maryland, U.S.A. Visitors will find stone buildings along the main street in both communities. Both are nestled in valleys near public parklands. Both are tourist destinations. And both are situated on waterways and prone to damaging floods.
Pickering, in the drainage of the North York moorland, had considerable success in addressing its flood problems in recent years, but not in the big, costly way you might expect.
After consulting with experts, the townspeople rejected a large, concrete wall they considered unsightly and could not afford. Instead, they built 167 porous dams of logs and branches and 187 smaller obstructions, made from bales of heather, to slow the flow of water. They planted trees and found a way to impound flood water for slow release through a culvert.
“Pickering pulled off protection by embracing the very opposite of what passes for conventional wisdom,” journalist Geoffrey Lean reported in the Independent. “On its citizens’ own initiative, it ended repeated inundation by working with nature, not against it.”
The cost of the project was about $2.6 million.
Ellicott City, of course, has faced a threat approaching existential, with two catastrophic floods since 2016 costing millions of dollars in damages and lost business. The ambitious plan for saving the town, rolled out by Howard County Executive Calvin Ball last spring, includes razing buildings on lower Main Street, widening a river channel and boring a tunnel to divert the water that cascades into town with each storm. The initial cost estimate landed somewhere between $113 million to $140 million.
The plan for Ellicott City does not include beavers.
Pickering, on the other hand, is already there.
No joke.
Two beavers were released last year into a forest to build dams and help slow the flow of floodwater into the area. Just last month people who live in Yorkshire saw results. A storm by the name of Dennis came through and dropped what meteorologists call a “weather bomb” across England, with 90 mph winds and a one-day rainfall equal to what normally falls in two weeks. The storm caused extensive flooding, but apparently beaver dams upstream augmented the sticks-and-heather flood control already in place around Pickering.
“Beavers introduced to Yorkshire in 2019 may have prevented Storm Dennis flooding with their dams,” declared the Yorkshire Post on Feb. 20.
Alan Puttock, an environmental researcher from the University of Essex, proudly displayed that headline in Hunt Valley last week as he presented research at BeaverCON 2020, a gathering of professionals engaged in managing beavers and reintroducing them to places where their dam-building could benefit humans.
While the research is not complete for the Pickering area — the newspaper headline might have been more speculative than scientifically conclusive — Puttock presented other examples of Eurasian beavers doing their part to control flooding.
With climate change comes more extreme weather — from floods to drought — and their advocates believe beavers can play a role in softening the effects of both. Beaver dams slow flows and prevent flash floods. In drought, the dams act as slow-release reservoirs of fresh water.
“It’s not a silver bullet,” Puttock says. “But it’s part of the answer.”
For a few centuries, humans have thought of the beaver either as a source of fur or as a nuisance, or not thought of it at all. That’s changing. In England, the once-native beavers have been reintroduced to areas their ancestors inhabited 400 years ago, and researchers like Puttock have been evaluating the benefits of their engineering skills.
In 2011, in Devon, a pair of beavers were released into an enclosed, 7-acre woodland that had been used for farm drainage. In due course, they built not one dam but a series of 13 dams. The dams resulted in a mosaic of ponds and canals that, from the sky, came to resemble a rich wetland.
Research shows that the ponds produced the desired effect; they slowed the flow of water through the area during heavy rains. Additionally, the ponds captured tons of sediment; water entering the beaver-created ecosystem carried three times the amount of sediment as water leaving the area. And the beaver ponds captured a significant amount of nutrients (phosphorus and nitrogen) that would otherwise flow off the farmland and downstream. So, water quality improved.
There’s more. When beavers build their dams and ponds, they create new habitat conducive to greater botanical and wildlife diversity. That’s why The Beav is known as a keystone species. That’s why the world was a very different place when they were around — before millions of them were trapped, before they disappeared from vast stretches of North America, before we filled in wetlands, before we built homes and driveways and highways in places we should have left alone.
So much of human activity causes flooding, it’s exciting to think about the possibility of bringing back beavers, deploying them where needed and where it makes sense, and letting them restore the landscape to its natural best.
We could consider it a team effort — combined human and beaver ingenuity to address serious challenges in land use, water quality and flood control.
Could beavers have spared Ellicott City its recent trauma? I don’t know. But I know we’ve tried man-made solutions for a long time. Maybe it’s time to include a naturebased one.