Trying to guard against road erosion
HOUGHTON COUNTY — Vegetation is a key element in preventing landslides and erosion but when it comes to road washouts like those seen during the Father’s Day flood there isn’t an easy solution.
Roots help hold soil in place with lightweight and deep rooted plants making good drainage ditch choices but plants can’t be grown in a blacktop.
Not all positive, vegetation can slow down water flowing through a ditch but this raises the water level causing it to overflow on the road, said Brian Barkdoll, civil and environmental engineering professor at Michigan Technological University. Once the ground reaches a certain level of saturation the water isn’t absorbed anymore, development can prevent saturation as well.
“When we develop land we put roofs and parking lots and those surfaces don’t allow that water to infiltrate into the soil anymore 100 percent of the water runs off into streams or into sewers so whenever we develop we’re creating more runoff and perhaps flooding,” Barkdoll said.
Though more of a problem for major cities the sheer amount of rain overwhelmed the normal systems.
“The huge rain and the steep slopes for us was sort of a double whammy,” he explained.
Now the rebuilders are left trying to stop further erosion before winter and during the spring melt.
Houghton County Road Engineer Kevin Harju has a lot to consider with limited supplies.
“We don’t want raw earth without any vegetation but at this point, we’ll be building up and re-establishing the roadways,” Harju said. “When we reconstruct them there will be some exposed dirt but we won’t be addressing that until the road is back to functioning.”
Mulch can be used for moisture and erosion elimination but the use is limited. Silt fences are common but the amount needed is more than time or supplies available.
“We’ll be working on that all summer long and into the fall especially the areas we probably won’t be able to repair until next year,” Harju said. “We’ll have to figure out something about how to stabilize those to prevent future erosion for the spring thaw.”
Many of the failures were due to fast-moving water undermining the gravel road edge, and from there the blacktop.
Culverts were overwhelmed or blocked, causing water to find a new path.
“The culvert pipes weren’t able to handle the flow and the culvert pipes overtopped and essentially you would have a scouring path which would erode the road material from around the pipes and in many cases eroded so much where the entire pipe went down the stream,” Harju explained.
Infrastructure is not built in preparation for 1,000-year storms, like the Father’s Day flood, due to the cost and feasibility.
However, some improvements are being made, with the Department of Environmental Quality approving larger culverts for several streams.
Harju urges residents to drive carefully and be patient as the repairs are made.
“It’s going to be a long road to recovery,” he said.