The W. Darcy McKeough Floodway is the largest flood diversion project in Ontario. The floodway was completed in 1984 to reduce the threat of flooding in the Town of Wallaceburg. The floodway is situated approximately twelve kilometres north of Wallaceburg in Sombra Township. It consists of an earth fill dam embankment and concrete control structure housing two vertical sluice gates. The grass lined diversion channel stretches seven kilometres west to the St. Clair River. Near the channel outlet, a concrete drop structure reduces the energy of the diverted flood waters before entering the St. Clair River. The drop structure also separates the St. Clair River from the normally dry channel.
The control gates remain open under normal flow conditions, but when Wallaceburg is threatened by flooding, they are closed and divert the flow down the diversion channel. The McKeough Floodway is capable of controlling all flood water upstream of the dam by diversion and temporary storage. The floodway is located such that it controls approximately 37% of the East and North Sydenham River drainage basins upstream of Wallaceburg.