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Manitoba from the Air
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River Capture on the Souris River South of Wawanesa


In immediate post-glacial time, a river flowed along the southern edge of the Tiger Hills (part of the Darlingford end moraine) occupying a spillway that now contains the Souris River, Langs Valley, Pelican Lake and Lorne Lake. The spillway used to carry water from glacial lakes, Souris and Hind, in the west to glacial Lake Agassiz in the east. At that time the proto-Souris, a tributary to the Assiniboine, was extending itself southwestward by headward erosion into, and eventually through, the Tiger Hills, possibly occupying an old glacial melt water channel through the hills. Eventually the proto-Souris met up with and captured the flow of the river in the spillway.

Today the Souris 1 takes a sharp bend at the elbow 2 and then flows through the Tiger Hills 3 in a steep-sided gorge. A small, unnamed stream 4 flows westward against the original flow to join the Souris at the elbow. Above the elbow, the Souris has incised a steep-sided inner valley into the floor of the spillway, the sides of which can be seen to the north 5 and south 6. On the north side a terrace 7 represents a former water level in the spillway. The south side is broken by two small gullies 8.

Since capture, the Souris has eroded rapidly through the end moraine of the Tiger Hills into the underlying shale that can be seen at a sharp bend in the river 9. Slumping has occurred on the west side of the valley 10. The river’s speed of the flow is fast for a prairie river and shallow rapids can be seen on this summer image 11. The south bank (north-facing) is heavily wooded but the north side—south facing and therefore drier—is covered by a mixture of grasses and trees, the latter in evidence in wetter “draws” 12. Both sides of the gorge through the Tiger Hills are thickly wooded, but the hills themselves have patchy woodland surrounded by grass.

A gravel road, PR 346 13, runs north/south across the area with a rare—for southern Manitoba—hairpin bend 14 on the south side of the spillway.


Figure 3.41

River Capture on the Souris River South of Wawanesa