The overnight storm on June 28-29 dumped 8.22 inches of rain on Baldwin.
The historic flooding that followed washed out bridges, caused the closure of over 50 roads and pushed St. Croix County to declare a state of emergency. To the northeast, Emerald, Wisc. recorded over 9 inches of rain in less than 24 hours.
“I’ve talked to people who’ve lived here their whole life and they haven’t seen water that high,” said Kasey Yallaly, a fisheries biologist with the Wisconsin Department of Natural Resources. “I’m not sure of the actual magnitude, but I’ve heard some say it was a 500 to 1000 year flood.”
Yallaly works regularly on the Rush and Kinnickinnic Rivers, St. Croix County’s most well-known trout streams. She said the Rush was hit the hardest by the storm, in particular a stretch on the lower Rush south of Highway 10.
“It looked like someone set dynamite off on the stream banks,” she said. “It was just ripped to shreds.”
Major rain events like the June 28 storm can have lasting effects on trout streams. Adult trout populations rebound fairly quickly after flooding, but juvenile fish can sometimes experience high mortality rates.
“They just can’t handle the flows like the adult fish can,” Yallaly said.
The Kinnickinnic River peaked at 3 p.m. on June 29 at 6,030 cubic feet per second (cfs). It generally runs between 140-150 cfs. With water levels that high, many young-of-the-year trout get washed out or stranded in pockets of water that eventually recede and die. In a normal year, Yallaly and her colleagues would sample the Rush following a storm like that to record fish numbers, but because of the COVID-19 pandemic, they’ve been unable to take on the projects.
“Because of COVID, we’ve been restricted to working in two person crews,” Yallaly said. “The Rush is one of our larger streams that normally takes up to ten people to sample. So we haven’t been able to get into these larger rivers to sample after the flood.”
Yallaly is confident however that the adult populations have rebounded well and said she’s been talking to anglers almost every day that are catching fish.
“The adult fish fair fairly well,” she said. “They should go back to their normal habitats within a week or two of the water receding.”
Erosion is also a major concern following floods, with certain areas being more susceptible than others.
“It kind of depends on what the land use is (on that part of the river) and what kind of shape it was in before the flood,” she said. “Some of those areas probably already had erosion going on and then the flood came and there was nothing to hold the banks.”
With erosion comes sedimentation, which can cover up critical trout habitat. However, floods can also remove existing sedimentation, revitalizing holes that have silted in.
“Pools that used to be really deep but had been filled in over the years, this flood scoured and washed them out,” Yallaly said. “And now they’re really deep, nice habitat again.”
Stream restoration efforts are a major focus of the DNR. Rebuilding banks and streambeds can help prevent erosion when floods come through, but Yallaly and her crew aren’t always able to access the land that needs restored.
“We can only work on land that we either own or have an easement on,” she said. Restoration efforts on the remaining areas are up to private landowners, and oftentimes these portions of the rivers go overlooked. Stream restoration is very expensive, and the hefty price tags mean privately funded projects are often unsustainable. The Natural Resources Conservation Service (NRCS) offers a cost share program to private landowners who’re interested in lightening their financial load on a restoration project, but that only goes so far.
The Fisheries Management Section of the DNR does have an excellent easement program that can be a perfect fit for landowners looking for assistance with a restoration project. Through the program, the DNR pays a landowner a one time, per acre fee for the easement, based on current land prices. In return the easement is open to public access for fishing, and it gives the DNR the right to do a trout habitat project on that land, with no cost to the owner.
“Depending on the stream, what kind of shape it’s in and the length of the easement, it could be well over a $100,000 project that comes at no cost to the land owner,” Yallaly said. “Plus they get paid for the easement.”
These easements benefit land owners, provide public land access, and can help prevent major erosion and sedimentation issues when floods occur.
“It’s a win-win for us and the land owner,” Yallaly said.
C.L. Sill can be reached at email@example.com or on Instagram @thewingbeat