By Lynn Keillor
Randy Brock's idea of a perfect spring day involves a fly rod, an assortment of flies, crafty trout, and a secret spot on the upper reaches of the Whitewater River. Brock is among countless trout anglers who have found favorite fishing places along this river in southeastern Minnesota.
The fishing just keeps getting better for anglers who pull brook, brown, and rainbow trout from these cold waters. "Last season was probably the best angling we've had down here for 20 years in all sizes of fish. And quite a few larger fish," says Steve Klotz, Department of Natural Resources Lanesboro area fisheries supervisor. "And this isn't just my opinion. We're hearing this from a lot of anglers."
From the look of the Whitewater River in August 2007, a person could hardly have imagined that any fish had survived the 17-inch rainfall and flash flood that tore out trees, moved bridges, and washed away sections of a county road. In some places, the river abandoned its channel and carved a new path for itself. Whitewater State Park lost a part of its campground.
Land-altering floods are as native to this area as brook trout. Water has been carving this geographically unusual area for more than 800,000 years. But DNR fisheries supervisor Steve Klotz suspects the land and waters would have responded differently to heavy rain in presettlement times, because the ecosystem had a better ability to absorb it. When European settlers arrived in 1851, the valleys were forested. Prairie grasses and forbs covered blufftops and lined riversides. As settlers removed native vegetation to make way for crops and used hills for grazing livestock, soil erosion and flooding began. In 1938 the valley town of Beaver flooded 28 times. Beaver was finally abandoned and subsequently buried with silt in the 1950s.
In the late 1930s, the Department of Conservation implemented conservation measures, such as tree planting on slopes. Farmers started terracing, strip cropping, and planting cover crops, which decreased erosion.
Today, sediment is still a culprit in the effort to maintain a healthy river system, says Ian Chisholm, DNR stream habitat program supervisor. "What you have is a lot of farming, reduced and altered riparian lands, and, eventually, a lot of sediment coming off the land, being deposited in the channels of the lower reaches of the Whitewater." Over time, sediment builds and confines the channel. Water moves faster in the confined channel, resulting in more sedimentation and erosion—making the river system less stable.
Since 1996 half of southeastern grasslands have gone back into row crop production, according to a U.S. Geological Survey report. Some researchers worry that sediment erosion and runoff may have increased because of land use changes. Chisholm says the amount of sediment now moving through our rivers is likely much greater than pre-1930s levels.
Anglers and biologists wondered how the physical alteration of the river would affect life below the water's surface: How would aquatic organisms survive and redistribute themselves? "You can imagine what we, and everyone else, thought," Klotz says of the destruction. "We thought it was going to take three, four, or even five years for the trout to recover from this." But the fish have proved resilient, and the Whitewater River has shown a remarkable ability to reshape itself after the flood.
John Huber, supervisor at the DNR Crystal Springs Hatchery, observes the river from his monitoring station—a phone-booth-like structure on Whitewater's south fork. "I've seen stuff come and go," he says, referring to his 36 years at the hatchery.
Before the 2007 flood, he watched fly anglers pull trout from a small pool just below a little riffle run. "Now I call it Lake Crystal," he says. At this spot, raging floodwaters chewed away the riverbank, then exploded over it. The river nearly washed away the monitoring station, which stood about 45 feet from the original channel. As the water receded, it left behind this stagnant, muddy pool with steep banks of exposed soil.
"But now as that mud continues to fall in on those sharp banks, it's building back a narrower channel, very slowly, which will eventually narrow the stream," he says. "The river will cut back down to the rock that used to be there. The bank along the stream, instead of being 6 feet high and susceptible to erosion, will be more gradual, grass-covered."
The DNR plans to let nature perform its own recovery on this quarter-mile stretch of river within the Whitewater Wildlife Management Area. Huber predicts that 20 years from now the area will look much less severe. Grasses are already starting to fill in some bare spots.
"But [the pool] looks like heck now," he says. "Short term it looks terrible, but long term it may not be as bad as we think."
For Whitewater fish populations, the turnaround after the flood was so quick that Klotz doesn't even think the word recovery is appropriate. Eight months later, the brown and brook trout had a record spring hatch.
It's hard to place an exact number on fish population changes, says Klotz. "It takes a while to try to assess something like that," he says. "We have very good populations of brown trout, and the brook trout populations are doing really well.
"Flooding is good for a river. That's what rivers do," Klotz says. High and fast waters form a new river channel and move sediment. The process creates new stream habitat. The 2007 flood may have made more than 1,000 years of natural alterations in a 24-hour time period, he speculates.
"From a human standpoint, there was an awful lot of recovery that needed to be done. The infrastructure damage was significant," Klotz says. "But from a fish community standpoint, flooding is a part of what happens naturally. "Granted, this flood might have been a once-in-2,000-year event. It's not likely that anyone will see this again in a lifetime or two."
Whitewater's fishing experts have not been completely surprised that trout can survive flash flooding—after all, trout have already survived changes such as roads, bridges, and culverts that slowed and altered the river. But how they survived this flood remains a mystery.
"I don't know exactly what they do," Huber says. "Considering the number of fish that are in the stream, after a flood of that proportion, you'd think that you'd walk around and find these brown trout laying around everywhere. And you just don't."
Huber speculates that fish searched for areas of least resistance, whether behind a rock, in an eddy, or up a tributary. Because the rate of water flow varies at different depths, fish could have hunkered down or simply rode the flood to its outer edges as water overflowed the riverbanks.
Just as incredible, their food source survived as well. "You'd expect, with all these boulders rolling down the creek, that every macroinvertebrate in the stream would be washed and wiped out too," Huber says. But they weren't. "It makes you feel small when you have 40 years into fish and you still don't understand what's going on," he says.
There were casualties, though. The spawn class of 2007, made up of 2- to 3-inch fingerlings at the time of the flood, was wiped out. However, the loss of a spawn class isn't unusual, and Klotz was already expecting low numbers due to heavy spring meltwaters.
"We had to make some quick decisions," Klotz says. Fisheries biologists ordered additional brown trout fingerlings from the hatchery the following spring, just in case. In retrospect, he says, it might not have been necessary. "It was an easy way to make sure we didn't have a bigger problem." But fishery experts got a pleasant surprise: their counts showed a record number of hatched trout. They speculated that rushing waters scrubbed the river clean, removing buildup and increasing oxygen levels, which made for prime spawning.
Since the flood, spring spawn counts have reached near-record levels, Klotz says. "The fish took full advantage of the clean riffles for spawning." Light spring runoff since the flood has also protected young hatchlings.
The flood showed how restoration work over the past 70 years has made the Whitewater River healthier and more resilient.
Much of the DNR's restoration work had pushed the water back into natural channels and reduced sediment buildup. The 2007 flood tested some of these water projects, says Ian Chisholm, DNR stream habitat program supervisor. Some worked, others didn't. For example, a berm that separated the Dorer Waterfowl Pools on the lower Whitewater was washed out. Another restored section with grassy banks held up. Because native grasses have deep root systems, they held fast and prevented soil erosion in the face of the flood. As a result, when the waters receded, the river was able to return to its natural channel.
The Hiawatha Chapter of Trout Unlimited had done 18 habitat improvement projects on the Whitewater, says chapter president Brock. Most of them involved stabilizing riverbanks and creating overhangs for trout to hang out in the shade. They also graded sharp riverbanks to gradual angles so the rising river could spread out in a more natural way to its floodplain, rather than acting like a chute that funnels water and increases velocity.
"With a couple of exceptions, our work didn't get washed away," Brock says.
According to Brock, the flood didn't change the urgency of his chapter's restoration plans, but new funding from the state has increased the scope. Prior to the flood, the group used private funds and government grants to restore up to 3,000 feet of river per year. Using dedicated outdoors funding from the recently passed sales tax amendment, the Lessard–Sams Outdoor Heritage Council granted $2 million to Trout Unlimited for restoration projects on streams including the Whitewater.
Since the flood, DNR trout stocking has continued in the Whitewater at usual levels, Huber says. About 20 percent of trout in the river comes from hatcheries. The remainder comes from natural reproduction.
But while there are plenty of fish in the river, the trout may not be in their old haunts. The flood filled in some pools and created new ones elsewhere, meaning that ye-olde fishing hole may no longer exist, Huber says. He tells anglers to rediscover the river.
"The fish have moved to fit the habitat," Huber says. "Anglers just have to relearn the stream."