July 11, 2016 Storm Brings Flooding to Area

On the night of July 11, a severe rainstorm struck the Eau Claire Lakes Area, saturating woodlands, farms, lake properties and communities from Hayward to the Ashland area and Lake Superior overnight.

The next day we awakened to damage from 10 to 13 inches of rain that washed out roads, raised lake levels so high that docks and pontoon boats floated away, shorelines suffered and a man died near Cable. Contributing to the rainfall severity were rains that occurred some days before the torrential rainfall saturating the soils.

Rains this severe have not been experienced in a long time. Ron Kofal, a life-long resident of Gordon living near Lower Eau Claire Lake, has never seen the Eau Claire River this high. Highway 27 to Hayward from Barnes was closed due to water covering low areas and Highway 77 was closed between Hayward and Minong.

Bob Lang, Town of Barnes Roads Foreman, reported that the day after the deluge, several roads had washouts or water running over the road, including Denver Road, Tars Pond Road, Pease Road, James Road, Lower Lake Road, Pease Resort Road, and North Beaver Trail in Potawatomi.

There was a dramatic washout of part of Denver Road a mile or so south of Lower Eau Claire Lake and Cranberry Lake. The Ounce River, pronounced “oonz”,  runs close to the road a short distance from Cranberry Lake Road. Commonly after rains in the spring, the Ounce spills over its bank and floods the woods draining through a culvert under the road  to the north side of the road into another woods and wetland downhill. What happened after the torrential rain of July 11 created more than that; a potentially lethal hazard.

Lang reported that by the evening after the heavy rain, the water rushing over Denver Road had dropped “a couple of feet” but was still two feet deep.

I visited the Denver Road site a few days later and saw that trees and bushes on the side of the road had dried brown mud extending five feet high above road level, indicating that the water that had been rushing over the road days earlier was five feet deep where the Ounce River bends south very close to the road.  The accumulated logs and brush bent against woodland trees evidenced a very powerful, high velocity flow. The five foot gush of water obviously surpassed the “too small” culvert’s capacity and flooded over the road, causing a crater on the south edge of the asphalt road, undermining it so that approximately 20% of the road’s width was missing asphalt for a stretch of maybe 20 to 40 feet.

Where the Ounce River is closest to the road and bends southward away from the road, there is a small unnamed tributary entering via its own small culvert under Denver Road where some people trap mink. It is usually a barely trickling wooded channel. Post-deluge markings show it was a raging stream, several feet deep that undermined a tree that became up-rooted and fell across Denver Road.

Luckily no vehicles tried to pass through Denver Road when water was rushing over the road following the deluge. The site is a good example of how a flash flood can suddenly appear and potentially drown people who accidently or purposely drive into the water. It is also a lesson that culverts should be overbuilt and oversized to handle major rainfalls like this one.

Even more dramatic was the washout of a section of State Highway 63 just north of Grandview and Drummond. Luckily no car traveled on the site during the rain as it collapsed underfoot or ran over the edge of the precipice.

The three dams of the three Eau Claire Lakes held back the water well.

Mooney Dam impounds water to form Lower Eau Claire Lake and rose at least 7 inches immediately after the heavy rain. According to Mark Schroeder, Douglas County Parks and Recreation Supervisor, on the day before the deluge of July 11, the lake level at the dam was at 1045.5 feet above sea level. The target, a DNR order, is for 1045.44 ft. so it was an inch or so above target.
Douglas County Parks and Recreation Department staff measure lake levels at the dam daily and on July 12, the morning after the deluge, the level was 1046.1 ft (7.2 inches above target). A stop log was removed to let more water flow through the dam. That night it was likely higher than 7.2 inches since it takes a while to rise at the dam after a rain on our multi-lake lake chain.

The lake level was lowered an inch or so daily after that by removing stop logs one at a time, purposefully at a cautious, slow rate to prevent dangerous and damaging rises of the river downstream where levels were at record high already.

Schroeder stated that we were lucky that the heavy rain occurred this year instead of last year when Mooney Dam was being repaired. During repair work only half of the dam carried water while the other was blocked by a coffer dam to permit work replacing the lateral concrete abutment. Core sampling had shown that the lateral abutment contained crumbling concrete. Theoretically that could have weakened the dam sufficiently to result in major leaking or failure if the deluge had occurred last summer.

Surface drainage at the county park at Mooney Dam caused a deep gully where runoff flowed over the bluff into the Eau Claire River.

Many cabin dwellers reported various types of damage due to the high lake levels. At Upper Eau Claire Lake, Bob Cochrane estimated the lake level rose approximately 8 to 10 inches and seemed to drop an inch per day on subsequent days. Bob Cochrane and Jim Bakken noted wood docks displaced and erosion of shorelines around the lake. Cris Neff reported that a pontoon broke from its mooring and floated across the lake. Bob Cochrane noted that Upper was “murky” and that using the Secchi Disc at the usual “deep hole” at the north end showed that water clarity was reduced from 20 feet to 14.5 feet.

Tom Krob estimated that Robinson Lake was 7 to 8 inches above normal. Carol Lebreck reported that Bony Lake levels were quite high with levels still at an estimated 4 to 5 inches above normal 10 days later.

Lake levels persisted at high levels 7 to 10 days later at several lakes, especially at Upper and Middle Eau Claire Lakes, where dams do not have stop logs to lower the lake levels. Because high speed motorboats can create high wakes that cause shoreline erosion, the Friends of the Eau Claire Lakes Area issued a high water alert to boaters that “Minimizing your motorboat wake will help protect shorelines from erosion during these times.”

The deluge of July 11 resulted in a lot of damage and created potentially lethal flash floods and road closings. It brought attention to the future need of better preparedness.

–Ted Eastlund