Page 506 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

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15.1a
Stream channels meander, or curve
from side to side in a snakelike pattern, where a stream’s
gradient is low and it flows through fine sediments. Meanders form
because the portion of the stream with maximum velocity shifts from one side of the stream to the other as the stream bends, thus affecting erosion and deposition along the
stream’s banks (GIA 15.1). Through these “scour-and-fill” processes, a meandering stream moves position laterally across its valley and creates a distinctive landscape (GIA 15.2).
PROFILE OF A MEANDERING STREAM
The cross sections show how the location of maximum flow velocity shifts from the centre along a straight stretch of the stream channel to the outside bend of a meander. The oblique view shows how the stream erodes, or “scours,” an undercut bank, or cutbank, on the outside of a bend, while depositing a point bar on the inside of the bend.
[Vladimir Melnikov/Shutterstock.]
Maximum velocity
Areas of maximum velocity
Point bar deposition:
On a bend’s inner side, stream velocity decreases, leading to deposition of sediment and forming a point bar.
15.1b
ACTIVE EROSION ALONG A MEANDER
Notice how this stream in Iowa has eroded a steep cutbank on the outside of a bend.
Explain: Explain the relationship between stream velocity, erosion, and deposition in the formation of a meander.
Pool (deep)
Undercut bank erosion:
Areas of maximum stream velocity (darker blue) have more power to erode, so they undercut the stream’s banks on the outside of a bend.
Cutbank
[USDA NRCS.]
Visit the Study Area in MasteringGeographyTM to explore meander and oxbow lake formation.
Visualize: Study a geosciences animation Assess: Demonstrate understanding of meander and of meander and oxbow lake formation. oxbow lake formation (if assigned by instructor).
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