A wing dam is a manmade barrier that, unlike a conventional dam, only extends partway into a river. These structures force water into a fast-moving center channel which reduces the rate of sediment accumulation while slowing water flow near the riverbanks.
The Mississippi River in North America has thousands of wing dams which were originally constructed to reduce the amount of dredging required when the main navigation channel was maintained to at least 4 1⁄2 feet (1.4 m). Since that time, additional conventional dams have been built to increase the water level in the river, doubling the depth of the navigation channel to 9 feet (2.7 m). The wing dams still serve their purpose, but to a lesser extent than before.
While wing dams assist in assuring that rivers are navigable, they can also pose a threat to boaters. Many wing dams in the Mississippi are usually underwater and may be difficult to see, but can be easily hit by propellers or other parts of a vessel. On the other hand, fishermen intentionally fish the waters downstream of wing dams.
Wing dams are typically constructed so that they point slightly into the current (meaning that the riverbank end is slightly upstream of the riverward end).
- Groyne. A wing dam is a type of river groyne (or groin, in US usage).
- Weir. Wing dams that are designed so that water can flow over them at times of high water are a type of weir.
- "Chapter 5: River Training Structures and Secondary Channel Modifications". Upper Mississippi River System Environmental Design Handbook. US Army Corps of Engineers. August 2006. Retrieved 2012-08-10.
- "Boating on the Big River". Mississippi River Guide. Minnesota Department of Natural Resources. 2011.