High water on Minnehaha Creek as local climate gets wetter

Wetter spring now the norm, climate experts say

Minnehaha Creek floods trails near West 51st Street & Minnehaha Parkway.

After six years of record-setting precipitation — a local sign of climate change, experts say — Minnehaha Creek is again overflowing its banks.

“You can sure hear sump pumps running,” said Lynnhurst resident Scott Eller, sitting on his front steps overlooking a spot where rising water has covered the trails.

“There are a lot more fish. Look at that tree stump. You’ll see a log move. That’s a bass, I believe,” said Mark, a Richfield resident fishing above a Minnehaha Creek outfall that sends water from Lake Harriet to the creek. It’s a secret fishing hole that would normally hold only small fish, he said, and now he’s seeing large bass and northern. While fishing, Mark said he was surprised to see kids jump off a nearby bridge into the creek.

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Carrie O’Brien said she recently swam in the creek near Minnehaha & 14th, where even strong swimmers struggled to swim against the current.

“It’s a little bit more dangerous,” she said. “All of us were against the edge, holding on to branches.”

Eller said he worried about the health of trees standing in water, as well as the risks for canoeists paddling outside the natural creek bed. (The Minnehaha Creek Watershed District currently advises against paddling —  any flows above 150 cubic feet per second are considered dangerous, and the creek is running double that.)

During the snowmelt last March, Settergren Ace Hardware at 54th & Penn saw a surge in people purchasing sump pumps, sandbags and Quick Dam flood barriers, manager Carl McGrane said. Pentair reports an uptick in sales of sump pumps and flood management products, particularly in the Upper Midwest.

“I’ve never seen it like this in 15 years,” said Jinna Zschunke, who walked on a sidewalk near a flooded trail. “It’s definitely alarming. What’s going to happen?”

Minneapolis is in the midst of a record-setting wet trend that started in 2013, according to the Minnehaha Creek Watershed District. While the creek’s median flow is typically 80-90 cubic feet per second at this time of year, the current flow is about 325. Lake Harriet is 6 inches above the ordinary high-water mark, and Lake Nokomis is 10 inches above the ordinary high-water level, according to the Park Board.  

“I think it’s been pretty clear that we’re seeing heavier precipitation with climate change,” said Craig Schmidt, service hydrologist at the National Weather Service. “We’re not quite as cold during the wintertime and we have a pattern that allows more air to come up from the south, which can contain more moisture than air coming down from Canada. When it contains more moisture, it’s able to snow a lot more.”

The Minnesota Department of Natural Resources’ climatology office said 2013–2018 was the wettest six-year period since record-keeping began in the 1870s.

Climate projections indicate that Minnesota cities will see fewer very cold days, more hot days above 90 degrees and more frequent heavy precipitation events, according to the University of Minnesota. Heavy rainfall has increased across the Upper Midwest, researchers said, and Minnesota is wetter in all seasons. Last year two Minnesota cities exceeded the state’s all-time record for precipitation, now at 60 inches.

“That’s an average rainfall in Miami, Florida. We’re getting much, much wetter,” said Tracy Twine, associate professor in the U of M’s soil, water and climate department, speaking at a January presentation to the Minnesota House of Representatives’ Energy and Climate Finance and Policy Division.

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Otto, Nat and Jeff Johnson (l to r) overlook a waterway connecting Lake Harriet to Minnehaha Creek near Lynnhurst Park.

“There is no place literally for the water to go,” said Tiffany Schaufler, project and land manager at the Minnehaha Creek Watershed District. After years of heavy precipitation the ecosystem has less storage capacity, she said.

Park Board Forestry Director Ralph Sievert said tree roots need oxygen in the soil to do well. The longer a root zone is flooded, the more likely it is that a tree could become stressed and leaves will brown. It would take a few years of annual flooding to see a tree actually die, he said.

“The trees still look okay. It’s just how long that water stands there and then also how long the soil is saturated,” he said.

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Willow, tamarack, river birch, alder and cottonwood trees can handle more water, according to Park Board staff, while sugar maple doesn’t fare as well. Mature trees tend to hold up better. Upland plants and Kentucky bluegrass can be killed when inundated with water, although the grass grows back quickly.

If banks are undercut next to paths, trails might see damage as well, and a project underway is repairing similar damage from flooding in 2014.

Damage to trails is rare, however, and the Park Board cleans and reopens trails as soon as possible when water recedes, Brent Kath, assistant director of asset management, wrote in an email.

Minneapolis Public Works staff said in a statement that they are monitoring stormwater pump stations along the creek and checking for debris on catch basins in low spots across the city.

“We’re doing our best to keep water flowing and hoping for dry weather,” said Rachael Crabb, the Park Board’s water resources supervisor.

“It’s kind of scary,” said one resident who declined to share her name in print, who said her basement at 51st & Knox flooded. All of her neighbors have sump pumps, and she will probably install one now, she said.

“Is this the new trend, that every four or five years it’s going to flood again? What measures can the city take to prevent it from flooding again?” she asked.

A proposed master plan for Minnehaha Creek includes strategies to manage flooding. Ideas include underground water storage, pollinator lawns and “re-meandering” sections of the creek to slow down the flow and reduce flooding.

Minnehaha Creek floods a field south of Burroughs School. Under a proposed master plan for the area, the field could be used for flood storage as needed.
Minnehaha Creek floods a field south of Burroughs School. Under a proposed master plan for the area, the field could be used for flood storage as needed.

“From what little I know, it will certainly help,” said Lynnhurst resident Tammi Cheever. “It looks like it would be extremely expensive.”

Cheever said she hopes proposals for more active recreation and water management strike the right balance so the creek remains a peaceful, natural place.

The Minnehaha Creek Watershed District repaired streambanks last winter; Schaufler said so far repairs are holding up well.

Following the 2014 flooding, the National Weather Service started providing the MCWD with precipitation forecasts every six hours to help manage the Gray’s Bay Dam that controls flow from Lake Minnetonka. (High water temporarily covered the spillway in recent weeks.)

Schaufler said creek communities petitioned to install the dam following severe flooding in Minneapolis in the 1960s.

“Lake Minnetonka is huge. That’s your biggest storage basin anywhere,” she said. “There is more storage on one inch on Lake Minnetonka than there is along the whole Minnehaha Creek. You can see why we care so much about what that water level is, because if it gets out of our control, and goes above the spillway … we can’t control that wall of water.”

Looking forward, Schmidt at the National Weather Service said he expects to see more weather extremes, often wetter than normal.

Lindsey Morris and Joseph Anderson picnic at Lake Harriet.
Lindsey Morris and Joseph Anderson picnic at Lake Harriet.

“We were very lucky. We flooded a lot but it could have been much worse,” he said. “We’re still pretty vulnerable because our soils are still really wet and our river levels are way higher than normal for this time of year. We’re still really susceptible. If we were to get a couple of more big rainstorms here in the next month, we could go right back up into higher flooding again.”

Council Member Jeremy Schroeder said that while the city partners with other agencies to address flooding, he asks individuals to think about how they can manage stormwater on their own properties.

“I think a lot of us have not thought about it, and now we’re being forced to,” he said.

The future of Minnehaha Creek: design proposals

01_Segment-1_Preferred-Concepts_DRAFT_190530-page-003
A proposal for the Lynnhurst area under the Minnehaha Parkway Regional Trail Master Plan. The Park Board is collecting feedback on the concept. Find more information at minneapolisparks.org.

 

01_Segment-1_Preferred-Concepts_DRAFT_190530-page-002
A proposal under the Minnehaha Parkway Regional Trail Master Plan for an area near Penn, Newton and Morgan avenues. The Park Board is collecting feedback on the concept. Find more information at minneapolisparks.org.

 

02_Segment-2_Preferred-Concepts_DRAFT_190530-page-002
A proposal for the creek near Nicollet Avenue under the Minnehaha Parkway Regional Trail Master Plan. The Park Board is collecting feedback on the concept. Find more information at minneapolisparks.org.

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