It’s well known that flood events have greatly deteriorated riverbeds and banks across Vermont – a kind of damage known as fluvial erosion. But many current river management techniques used in the aftermath of flooding can put rivers in an even more precarious state, according to river scientist Shayne Jaquith.
On Wednesday, October 16, at the Valley Players Theater in Waitsfield, Jaquith gave a presentation on river science and flood damage, called “Living with a Mad River: A History of Human Impact and How River Science Informs Us About Moving Forward.” The event was hosted by Friends of the Mad River.
Jaquith is currently the watershed restoration manager for the Vermont chapter of The Nature Conservancy. Previously, he was based at the Vermont Agency of Natural Resources (ANR) for two decades. Prior to that he was the former executive director of Friends of the Mad River.
Under its Rivers Program, the ANR recently analyzed over 5,000 miles of Vermont rivers and found the majority of them to be on the verge of massive erosion. “Our rivers are just very unstable. They’re primed to collapse,” Jaquith told attendees at his talk.
“We’re trapped in a cycle,” he said, in which human projects and investments encroach on rivers, weakening them and leading to flood damage, only to be followed by short-term river management efforts that essentially encroach on rivers even more.
These techniques include deepening river channels, smoothing out their “roughness” by removing sediment and debris (dredging), and straightening rivers out as they come into contact with investments like roadways and buildings. Each can increase the power of water flow through river channels -- especially during heavy rains, eroding rivers to the extent that development projects get severely damaged and homes get washed away.
These damages are ultimately more costly than damage due to water and sediment inundating buildings. Jacquith pointed out that property damage from future flood events in Vermont is estimated to exceed $5.2 billion in the next 100 years -- “So, it’s an expensive forecast,” he said.
His talk focused on some strategies for river restoration, like a recent project in which a natural resource management firm created over 30 wood-jams within a mile-long stretch of the West River in Windham County – essentially cutting down trees and letting them fall into the river at certain sites. This technique built the riverbanks up substantially, allowing water to slow down and spread out into flood plains, with the potential of reducing damage in lower valley communities during future flood events.
Wood-jams mimic the state of Vermont rivers prior to European settlement, Jaquith said – with “multi-thread channels” that meandered through wetlands, congested by the debris of beaver dams. “You need nooks, and crannies, and crevices, and wood, and you need deep pools,” he said when describing balanced, stable rivers.
Hiring sawyers to create wood-jams is relatively inexpensive for municipalities, he added, but these need to be carefully planned, as they could damage infrastructure when they move further downstream -- as they inevitably will. “Everything in river restoration is temporary. Those dynamic forces [of a river] are always at play,” he said.
Other long-term strategies for preventing river erosion and subsequent flood damage shared in Jaquith’s talk include increasing the size of infrastructure like bridges and culverts to withstand moving debris and protecting river corridors from future development. Vermont recently passed the Flood Safety Act, which will begin requiring permits for development projects proposed in river corridors a few years from now.
To learn more about river science and the implications for mitigating flood damage, listen to Jaquith’s talk in its entirety on Mad River Valley Television.
https://www.youtube.com/watch?v=FsbjhITUZOA)
