Flash flooding hits trout streams hard

  • Article by: Doug Smith
  • Star Tribune
  • August 25, 2007 - 9:19 PM

The flash floods that raged through southeastern Minnesota last weekend, causing seven deaths and widespread destruction to homes, roads, bridges and businesses, also altered the region's renowned trout streams.

The rainfall and flooding were historic. In many areas an estimated 13 to 17 inches fell in 24 hours — more than has ever been recorded in the state — turning placid streams into raging torrents that blasted everything in their path, including bridges and roads.

Some of the area's most popular trout streams were altered drastically. Creek bottoms were scoured, habitat destroyed. Some fish were washed downstream and left stranded in remote pools of water. Others could have been killed by the infusion of warm water polluted by farm chemicals, fuel and manure from feed lots.

Still, officials are hopeful.

"The trout population is amazingly resilient," said Steve Klotz, Department of Natural Resources area fisheries supervisor in Lanesboro. "I'm hoping the fish population withstood this event."

Klotz and his workers were trying last week to determine the extent of the damage and the impact to the region's fisheries. It will take weeks. Officials soon will begin surveying fish populations in some streams using electroshock devices.

But a cursory inspection shows a changed landscape.

"Streams like Rush Creek and the Middle Branch and South Branch of the Whitewater River, and Garvin Brook are absolutely devastated," Klotz said. "The habitat doesn't even resemble what it did before."

One example: "There's one spot in Rush Creek that used to be 15 to 20 feet wide with a deep hole," said Jeff Broberg, a geologist and president of the Minnesota Trout Association who lives near St. Charles, Minn. "It's now 80 feet wide with 2 inches of water."

Said Klotz: "The streams now are incredibly wide, and the depths are really shallow in places. There were places in Rush Creek where the flood plain was 400 feet of water across the valley."

The concern is that the wider, shallower waters won't be hospitable for trout.

Said Broberg: "We may not have seen an event like this in 1,000 years. It's just incredible. The water filled the Whitewater Valley at Beaver from bluff to bluff, 3 or 4 feet deep.

"It has totally flattened the stream bottoms, so there's no holes left. It filled them in with gravel, so we have flat water everywhere.

"It's amazing."

News not all negative

Many other areas received only 5 or 6 inches of rain. That caused some flooding, but the damage to those streams was minimal.

Klotz said the heaviest rains fell in the area of Interstate 90 from Rochester to Winona, inundating streams in portions of Fillmore, Winona and Houston counties.

"The streams along that belt really took a whooping," he said.

Other streams farther away in southern Houston County, southern Fillmore County and northern Wabasha and Goodhue counties weren't affected as much, Klotz said.

"Hay Creek should be OK, and some other smaller streams," he said. Trout Run, another popular stream, appears to have fared well.

Flooding can actually benefit trout streams by removing silt deposits. And that occurred last weekend in many streams. Still, this flood was different. Not only did the floodwaters remove silt, but in some areas they blasted out vegetation and habitat.

"Some places look like someone dumped a truck-load of 2- to 4-inch cobble into the stream," Klotz said. "It looks sterile. It's going to take a while for the food chain to recuperate."

Angling for answers

Curious to see what he'd find, Broberg fished Thursday in Trout Run and the Middle Branch of the Whitewater. He caught an 11-inch trout in Trout Run.

"It had four scratches from being banged around," he said. He saw two other fish.

The stream was changed.

"It really cleaned out the stream bottom; there was no silt," he said. "It widened the stream in many areas. But there were some deep scour holes. And some aquatic vegetation remained. I saw frogs and crayfish. I was encouraged."

But the Whitewater was different.

"I didn't even see a fish," he said.

Some good news

The only good news from the Whitewater was that habitat improvement projects done by the DNR and trout groups survived the onslaught of water, Broberg said. "Lunker structures" — manmade bank overhangs built from wood and rock, remained intact.

"I was impressed," he said.

So was Klotz. He said it appears many of the DNR's stream habitat improvement projects done over the years survived the flood, including a recently completed project on Rush Creek.

That project included 1,100 feet of shoreline stabilization and bank revegetation that withstood the blast of water.

"It's almost unbelievable," Klotz said.

That reinforces the belief that those projects can make a difference for trout habitat, he said. He's hoping landowners will be more apt to grant easements to the DNR so that more of those projects can be done.

The problem is it will take a massive amount of work to restore some of the hardest-hit streams.

"We could spend two years just trying to restore the Middle Branch of the Whitewater," Klotz said.

The DNR hopes to come up with a plan in the weeks ahead, once an assessment of the situation is completed. The agency routinely stocks trout in streams, and once the damage assessment is done, Klotz said, the DNR will have to decide where stocking is most needed.

Compounding the problem: The DNR's Crystal Springs trout hatchery was nearly destroyed by the flood, but one in Lanesboro wasn't damaged.

Broader issues raised

While the record amount of rain virtually guaranteed flooding, some say land-use changes — including intensive farming — likely contributed to the disastrous results.

"Much more land used to be in grass and hay," said Mel Haugstad of Preston, a retired DNR fishers manager and Minnesota Trout Association member. Those grasslands absorbed more water and reduced runoff. These days, more land is being planted with corn, he said.

Larry Gates, a retired DNR watershed coordinator, agreed.

"Had everything been in place with good conservation practices ... we would have seen some reduced flooding," he said. "I don't know how much."

For now, Klotz recommends anglers who plan to visit the area in the near future should use caution. Roads and bridges remain closed and many trees are down along some stream banks, making access difficult.

"Overall, it's pretty much a mess," he said.

Doug Smith •

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