WING DAMS

Piles of rock mark a wing dam on the Mississippi River.

WING DAMS. Wing dams are jetties of rock placed nearly perpendicular along river banks. Some are constructed to be visible at all times other than during floods. Other wing dams are submerged and usually are marked with buoys to avoid boating accidents. They are intended to stabilize channels and to keep water levels high in mid-river for barge traffic. Most of them were built in the 1930s and 1940s by the U.S. Army Corps of Engineers. During low water flow, the wing dams keep the channel deeper for barge traffic and increase water velocity in the center to create a stable, self-scouring channel.

Studies have indicated that wing dams may cause problems. Under flood conditions, the structures slow water speed and constrict the channel forcing flood levels to rise. A comparison (Criss and Shock) of flood stage levels of the middle-MISSISSIPPI RIVER (from the confluence of the Missouri River down to the Ohio River), and the lower Missouri River, both heavily lined with wing dams, to the Meramec River in Missouri, and the Ohio River at Cincinnati which are free of wing dams suggested that wing dams increased flooding. "Where none of this kind of engineering occurred (including the construction of levees), the records today look just like the records of 100 years ago," said Criss. "Such is not the case on the heavily engineered Mississippi River at St. Louis. Before WORLD WAR II, floods that reached 38 feet or higher at St. Louis were very rare, occurring only about every 50 years, but now flood stages of this magnitude occur every five years or so."

This diagram illustrates the layers of willows and rock used to create the first wing dams.

Piles of willows were needed to construct the dams.

Willows were woven together prior to submerging them.

Tons of rock were needed.

(All photographs were courtesy of Maury Anderson.)

(Technical assistance on all photographs was provided by Rebekah Godwin.)