You might remember that on valentine’s day I did a talk with Bob Boucher for the Oakmont Symposium in Sonoma. He was very excited that the final draft of this academic paper had just been released and talked about the difference this could mean to Milwaukee. Fittingly this research was paid for by a grant from the local water agency. Which is the kind of thing that makes sense but rarely happens.
UWM researchers find that beavers could be a remedy for downstream floods
A new study by two U
WM researchers shows that restoration of an animal that Wisconsin was known for 300 years ago – beavers – could be a part of the solution.
Enough of the dam-building animals living in the right spots along creeks and streams can alleviate flooding in some of Milwaukee County’s worst-struck areas, according to research by Qian Liao, an associate professor of civil engineering, and Changshan Wu, a professor of geography.
When beavers build homes, called lodges, in wetland habitats, they also construct dams to create a pond so that they can enter the lodge from under water. A significant amount of water backs up as the pond forms, and that hinders fast-moving water, which has a cumulative effect downstream.
Whoohoo! Everything about the opening is perfect, except for that line about Wisconsin knowing beavers for 3oo years. Hmm I’m thinking they’ve been around a bit longer than that. Maybe you want to check in with the Oneida or the Chippewa about that? They might have other opinions.
Bob Boucher, founder of the environmental advocacy organization Milwaukee Riverkeeper, proposed the study to officials at the Milwaukee Metropolitan Sewerage District, which funded the research.
“If there are hundreds of beaver dams distributed across the entire watershed, you have many locations where you can reduce the water flow,” Liao said. “And not just the volume, but also the timing, so that the combined delay at each dam has a significant impact on the downstream peak flow.”
Collecting data with their cellphones, Boucher, Holloway and students Max Rock and Madeline Flanner spent much of 2020 visiting 163 locations on the GIS maps. They made observations either by canoe or by hiking into areas at bridge road crossings to evaluate whether locations had ample food sources and the kinds of trees the animals use for building.
A cellphone app that Rock developed helped the team rank the locations by quality, based on all the data. What they found was enough habitat to support around 4,500 beavers – or about one family for each 100 acres of wetlands
That’s right. Bob is so skilled at maneuvering these things he got Milwakee sewage to pay for it and a student to develop a cell phone app that could study it.
Liao fed the model different scenarios of beaver dam activity at 52 locations that would provide the highest potential to reduce downstream flooding, while also having ideal conditions for beaver. According to the model, dams would reduce the peak flow by between 14% to 48%, depending on the details of the storm, but also on the dam location.
“For example, if the storm was relatively uniform across the entire watershed, then you would have the highest reduction of water flow,” he said. “But if the storm dropped most of its rain on southern areas of the river watershed, then dams located upstream where there’s less rain will have a diminished effect.”
How awesome is this research? Beaver dams can make a huge difference. But we need MORE OF THEM. That’s what I take away from this article.
“There have been other studies that showed the effect on flooding of introducing beaver dams, but those studies only measured the effect a few miles downstream,” Liao said. “What we did is a little different. We looked at it on the watershed scale.”
