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Table of Contents
Foreword
Preface
Glossary

Chapter 3: Geologic Structure and Landforms

3.25: The Assiniboine Glacial Spillway: Meanders and Abandoned River Segments

Here the Assiniboine spillway floor varies from under one mile (1.5 km) to over two miles (3.2 km) in width. The main river channel hugs first the southwest bank of the spillway 1, then the northeast 2, before transferring back the west bank 3. Two small abandoned meanders can be seen 4, but more obvious are long segments of the river that have been left behind by the migrating river 5.

The Assiniboine wanders across the spillway floor in a series of irregular meanders, leaving behind clearly defined meander scrolls 6. Part of the floodplain in the northwest has been reclaimed for agriculture and is protected from flooding by the main river channel by an embankment (dike) 7. Even so some of the land, the site of the old river channel, is too wet for agriculture 8.

The south and west bank of the spillway is steep, well-wooded and broken by only one minor gully in the south 9, whereas the north and east bank is less steep, not so uniformly wooded because of the dry microclimate on southwest and west facing slopes, as well as being broken by four major gullies 10 and many minor ones.

Flat land exists on either side of the spillway. In the west glaciofluvial materials pulled into northwest/southeast trending ridges underlie the surface 11. Linear sloughs occupy depressions 12, and the surface is covered by scrubland with patches of trees 13. East of the spillway much of the land is used for agriculture. Light-toned hillcrests can be seen in fallow fields 14. Roads follow the section lines of the DLS on flat land but are influenced by the topography on the spillway sides 15.

Figure 3.25: The Assiniboine Glacial Spillway: Meanders and Abandoned River Segments

Figure 3.25: The Assiniboine Glacial Spillway: Meanders and Abandoned River Segments

Figure 3.25

Vertical air photograph: A15527-134

Flight height: 20,000 feet a.s.l.; lens focal length: 152.26 mm

Date: October 7, 1956

Scale: 1:37,300 (approx.)

Location: Township 12 and 13, Ranges 25 and 26 WI

Map sheets: 1:250,000 62K Riding Mountain

1:50,000 62K/2 Hamiota