Duluth streams being fixed with future floods in mindLast June’s storm scarred more than 40 named streams in Duluth, 16 of which are designated trout streams. As they're slowly rebuilt, care is being taken that they can withstand another flood.
By: John Myers, Duluth News Tribune
Karl Koller walked along a small tributary of Knowlton Creek near Spirit Mountain on a sunny afternoon last week and pointed to one problem after another.
Last June’s deluge and ensuing flood had changed the path of the creek — eroding banks, tossing rip-rap boulders as if they were toys and cutting into the earth along the banks, exposing roots and causing huge pieces of hillside to slough downstream.
The problem, of course, was too much water too fast, not just from the rain but from how people have developed nearby and diverted water into the streams that never would have gone there before.
“Many of these streams were unstable to start. Then you throw in a 500-year flood, and everything breaks down,” Koller said.
Koller, a specialist for the Ecological Resources Division of the Minnesota Department of Natural Resources, was joined by Michael Geenen and Greg Jennings, engineers for Stantec Consulting, a stream restoration company, and Keith Anderson of the South St. Louis Soil and Water Conservation District.
Even before the flood, Knowlton Creek and its tributaries had been targeted for a special conservation project aimed at reducing the amount of sediment it sends down into the St. Louis River. Years of erosion from the Spirit Mountain ski hill, and the excess runoff from man-made snow each spring, had turned Knowlton into a chute for sediment to rush down the hillside and out into the St. Louis River estuary, covering trout habitat, clogging wetlands and contributing to the need to dredge the harbor downstream.
But last June’s storm had scarred the creek beyond anything before, as it did for many of the more than 40 named streams in Duluth, 16 of which are designated trout streams.
Now, slowly but surely, the city of Duluth, resource agencies and nonprofit conservation groups are moving to catalog the damage. Riffle by riffle, rapids by rapids, one clay bank at a time, natural resource experts are forming plans for how they will restore dozens of streams in the region back to some sort of normalcy.
For example, groups have asked for Minnesota sales tax-funded Legacy grants, some $6 million, to restore five different watersheds in the city, five of the hardest-hit trout streams.
“People need to be patient,” Anderson said. “It’s not going to look like it did before. But that’s not necessarily a bad thing.”
While it was streams across the region that spilled their banks and caused so much damage, it’s not necessarily Mother Nature’s fault. Development has worked to route too much water too fast into the waterways, by removing wetlands and adding impervious blacktop and concrete across the landscape. Then we confined streams to a fraction of their former flood plain because we wanted to build close by.
Anderson said the flood has created an opportunity to rework Duluth area streams back to a more a natural system — back to how they functioned before concrete and blacktop changed the landscape and before well-intentioned engineers began straightening streams and trying to hem them in.
“If we do this right, when the next flood comes, the damage won’t be as bad. The (natural stream) system will be able to absorb that shock,” Koller said.
The resource experts look at blown-out Duluth streams like Chester Creek and Mission Creek and see a chance to restore the waterways to their original flood plain. Streams need more than just a narrow, shallow channel for their normal load but also a low-level flood plain over which to spread flood water, usually once every other year or so.
Streams, the experts said, need to meander to work right.
“It’s the streams like Mission Creek (in Fond du Lac), where they tried to make it into a straight channel, the ones most impacted by human activity, that had the worst problems, that caused the most flooding,” Anderson said. “Now, Mission Creek has sort of reclaimed its old, meandering path. It’s reclaimed its old flood plain … Chester Creek the same way.”
Restoration work in many places will involve strategically placing boulders in the waterways as well as protecting slopes with woody debris and vegetation. In some cases, the path of the stream will be physically moved in an effort to restore a more natural path.
But it can also get more complicated. In the case of the un-named tributary to Knowlton Creek, Jennings said the project will involve raising the stream bed up, through a series of steps, to bring the water level closer to the original flood plain. As it sits now, the creek just keeps cutting deeper and deeper during floods, unable to meander.
“You have to look at these streams as systems. You can’t just look at trout habitat or sediment reduction or water quality and work for one end. You have to look at the whole system and work from there,” Koller said.
Jennings, who has worked on stream restoration projects nationwide, said engineers and contractors can do amazing things to restore the natural functions of streams to move water across the landscape without causing problems. All they need is a little space and lots of money.
“In streams that are not completely confined, we can do a tremendous amount of improvement to regain a natural stream flow,” he said. “The streams just need a little help. We need to get those natural flood plains back.”
This week's stories
Sunday: How the flood happened, the state of our roads and homes. Where are they now: Fond Du Lac
Monday: Restoring our streams. Where are they now: Skyline Parkway
Tuesday: A book about the Brookston flood. Where are they now: Knife River
Wednesday: Where are they now: Superior
Thursday: The state of our zoo. Where are they now: Thomson
Friday: Jay Cooke State Park