Skunk Creek flood basins pass the storm test
After a major storm in 1999, Two Harbors officials began working on a flood prevention project along Skunk Creek that could hold up to a 500-year storm.
In June, that storm came--and the flood detention basins and streambank stabilization that took more than a decade to complete passed the test.
"(The Skunk Creek projects have) saved the city and private landowners millions," said Mike Kohn of ICECOR, a Superior environmental engineering firm that designed the detention basins.
Two Harbors City Administrator Lee Klein agreed.
"It appears that they functioned quite well," he said.
While estimates of the costs of damages caused by the Flood of 2012 in northeastern Minnesota have exceeded $100 million, Kohn and others say the damage in Two Harbors could have been much worse than it was.
Flooding from Skunk Creek has had a long history. An article from the Iron Trade Journal (a forebear of the News-Chronicle) dated Jan. 2, 1908 tells of a lawsuit brought against the city of Two Harbors by a Mr. Sullivan for "injuries to his house in the flood (Skunk Creek) of September last." A jury awarded him $310.
The detention basins and stream bank stabilization along Skunk Creek are a more recent solution. On July 4, 1999, a 100-year storm occurred that dumped over 5 inches of rain on Two Harbors. The area's red clay soil and bedrock, land development and the ecological effects of logging contributed to increased runoff. Skunk Creek's water went from low-flowing to raging very quickly, according to engineer Keith Anderson of Lake County Soil and Water Conservation District, resulting in property damage.
After the storm of 1999, Two Harbors developed a stormwater management plan. The Lake County SWCD, which funded the project along with the city and the Great Lakes Commission, called for "several stormwater detention basins and installation of streambank stabilization along Skunk Creek."
Enormous basins were dug into the earth at the Two Harbors cemetery, on Battaglia Boulevard and on 19th Street. Truckloads of boulders, called riprap, were piled at the water's entry and exit points in the pits to control the flow of water back into the creek.
Riprap was also used near 7th Avenue, south of the train tracks. For years, storm water rushed down the creek and caused the erosion of the clay bank there.
Although effective, riprap is no longer the preferred material for this purpose, says Keith Anderson, although it is used under some circumstances. Current trends are toward the use of eco-friendly materials such as woody debris or logs to control water flow.
Two Harbors and the Lake County SWCD have also collaborated on shore stabilization near Flood Bay and the Burlington Bay Campground. This effort minimized erosion during recent storms, engineers said. Other areas along the shoreline did not fare as well.
Though the Skunk Creek basins worked, officials say they're not done with flood abatement.
"Lake County SWCD is conducting preliminary flood damage assessments across the county and seeking funding for shoreline stabilization through state and federal sources," said Jennifer Thiemann of the conservation district. "The worst erosion damage is along the Knife River, Stewart River and Lake Superior."