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Chapter 16: Water Resources

16.49: The South End of the Red River Floodway

The system designed to protect Winnipeg from floods consists of three major structural elements. “The largest is the Red River Floodway, a 47 km excavated channel that can divert up to 1,700 cubic meters per second (cms) around the city….A second channel, the Assiniboine Diversion 3 km west of Portage la Prairie, can divert up to 700 cms from the Assiniboine River to Lake Manitoba, relieving stress on the Red River through Winnipeg and providing protection along the lower Assininboine. Finally, the Shellmouth Dam and reservoir on the upper Assiniboine offers protection to Brandon, further controls the amount of water in the lower Assiniboine and provides a supply of water to maintain flow in dry year”[i].

Shown here is the northward-flowing Red River 1 and the entrance to the Red River Floodway 2. At this location the normal summer depth of water is 10 feet. An earth plug 3 across the entrance to the floodway is seven feet high to prevent ice from entering the floodway. Its crest is 27 feet above the river bottom. “The floodway can be used to carry part of the flow of the Red River but only when river levels rise to a point above 17 feet higher than the normal summer level”[ii]. The flow along the Red is controlled by the inlet control structure—a dam—across the Red 4. The floodway which bypasses Winnipeg to the east is 29 miles (46.6 km) long and involved the excavation of 100 million cubic yards (76.46 cubic meters) of earth 40 percent as much as the Panama Canal[iii]. At the eastern edge of this photo it is 2000 feet (609.6 m) from top edge to top edge. It reenters the Red River at Lockport, downstream from Winnipeg. Entering the Red River from the west is the small La Salle River 5. South of it extending west from the control structure is a dike 6 designed to prevent flood water from the Red River Plains entering the La Salle, gaining access to the Red River, in effect bypassing the floodway control and entering Winnipeg “by the back door.” This structure, given various names such as “Z dike” and “Brunkild dike” received great prominence during the 1997 flood when it had to be hastily extended west across the plain as far as Brunkild.

PTH 75 7 enters Winnipeg from the south, passing through the suburb of St. Norbert 8 just south of a cloverleaf 9 interchange on the perimeter highway (PTH 100) 10. Cars and trucks can be seen on the cloverleaf. East of the Red is PR 200 11 which crosses the floodway on a bridge 12. Building the floodway involved not only massive excavation, but also construction of numerous road and rail bridges across it, carrying power lines over it, as well as diverting the flow of the Seine River, a right bank tributary of the Red, under it. The wide irregular light toned line 13 in the south indicates the route followed by a gas pipeline, excavation for the line resulting in a lighter tone. Although it goes under the Z dike 14, PTH 75 15 and the Red 16, it just misses the floodway.

The long lot system of land division clearly influences field shapes that are long and narrow running back from the river 17, and road directions—west southwest/east northeast 18—especially east of the Red.

Figure 16.49: The South End of the Red River Floodway

Figure 16.49: The South End of the Red River Floodway

Figure 16.49

Vertical air photograph: A27254-12

Flight height: 13,300 feet; lens focal length: 152.063 mm

Scale: 1:25,100 (approx.)

Date: April 14, 1998

Location: Township 9; Range 3E

Map sheets: 1:250,000 62H Winnipeg

1:50,000 62H/14 Winnipeg


[i] Rannie, W. F. op. cit. 1996, 283.

[ii] The Red River Floodway. Winnipeg: Manitoba Natural Resources. Pamphlet, n.d.

[iii] The Red River Floodway. Winnipeg: Manitoba Natural Resources. Pamphlet, n.d.