HASTINGS, Minn. — The Army Corps has completed a $324,000 wing-dam notching project upstream from its Hastings lock and dam. By cutting out a section of the old rock dams – called “notching” — water is being diverted to encourage flow diversity for fish habitat. To mark completion of the notching project, the Corps plans a ribbon-cutting ceremony July 25 at 1 p.m. The project is the first in the nation under the Navigation and Ecosystem Sustainability Program. Expected beneficiaries are channel catfish, white or yellow bass, walleye, and paddlefish.
Wing dams. Extend from shore out to the divert water flow to navigation channels and keep the deep enough for boats and barge. Image: Maury Anderson
Wing dam profile
The Army Corps has 1,300 wing dams on the Upper Mississippi north from Guttenberg, Iowa. Some date to the 1860s. They divert water to main channel for navigation. When wing dams were built, the goal was a 4-1/2 foot depth. The lock and dam system of the 1930s brought the main channel to nine feet. Wing dams, also called wing dikes remain useful by force water into a fast-moving center channels. This reduces the rate of sediment accumulation, while also reducing shore erosion. There is a downside. Many of the jetties are hidden under the surface. Although marked by buoys, they tey pose a risk to recreational boaters. A plus: Quieter waters downstream of wing dams are great for fishing. There is a school of thought that wing dams are at fault for massive flooding, especially in the Lower Mississippi, by discouraging flows unto Upper Mississippi flood plain s and accelerating flows downriver.
Layered wood, stone. Wing dams were built by layering readily available willow logs and stone. It was primitive engineering by today’s standards but effective. The earliest wing dams are 160 years old.