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Chapter 3: Geologic Structure and Landforms

3.87: The Lake Agassiz Plain South of Roland

The plain left behind once Lake Agassiz retreated from southern Manitoba is one of the most extensive flat areas in the world. This high-level, small-scale photo covering about 133 square miles (344 sq km) gives a good impression of the plain that is almost completely flat except for an inperceptible decline to the east, towards the Red River. The slope results in a series of minor eastward flowing intermittent streams from north to south: Graham Creek 1, an unnamed creek 2, North Shannon Creek 3, Shannon Creek 4, Thornhill Coulee 5, and Deadhorse Creek 6. Several creeks have been straightened to increase the speed of flow; for example, Graham Creek 7, the unnamed tributary of North Shannon Creek 8, and Shannon Creek 9.

Until the beginning of the Twentieth Century this area was marshy and useless for agriculture until an intricate system of drainage ditches was constructed. The straightened steams are at the top of a hierarchy of drainage channels; at lower levels are hundreds of kilometres of minor channels not seen on this photo either because they are too small or because they run parallel to section lines. Although there is a limited amplitude of relief, minor depressions are wetter—and therefore darker—producing a mottled effect 10. Also two minor strandlines trending north-northwest/south-southeast can be seen 11, one of which is exploited for sand 12.

Once the soils were drained, they were excellent for arable agriculture. Consequently, apart from a few wooded, deciduous areas along creeks 13, the whole area is devoted to crop growing. Usually there are one, two, or three farms per section 14, their location being determined by the DLS system. The land is used intensively often with many fields in one section 15, in contrast with one to four per section in southwestern Manitoba. Wind is a problem in the flat area; consequently, nearly all farms have shelterbelts to north and west 16, and field shelterbelts have been planted in two locations 17. Road location is determined by the DLS system although PTH 23 18 detours around Roland 19. In this settlement roads are rather surprisingly oriented with respect to the DLS system rather than the CN railway line which passes through it 20. An abandoned line 21 enters Roland from the southeast and continues north.

Figure 3.87: The Lake Agassiz Plain South of Roland

Figure 3.87: The Lake Agassiz Plain South of Roland

Figure 3.87

Vertical air photo: A21852-12

Flight height: 24,100 feet a.s.l.; lens focal length 85.55 mm

Date: August 12, 1970

Scale: 1:81,200 (approx.)

Location: Townships 3, 4, and 5; Ranges 4 and 5 WI

Map sheets: 1:250,000 62G Brandon 

62H Winnipeg

1:50,000 62G/8 Miami

62H/5 Roland