Geoscience Reference
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Figure 3.6. Close up of a slackwater sediment terrace in Ord River Gorge. Note the
person (arrowed) in the right foreground for scale.
the thickness of the sedimentary units, suggests that if they are a result of just
one event then it would have been a flood much larger than any floods observed
in the region since European settlement. There are many studies of slackwater
deposits from around the globe published in the scientific literature. Examples
of just a few of these include Heine (2004), Wohl (1992b, 1994), Kochel and Baker
(1988)andBaker and Pickup (1987).
Plunge pool deposits
Plunge pools occur at the base of waterfalls. They are dish shaped fea-
tures eroded by the impact of the water onto rock or sediments. Their size and
depth are to a degree a function of the stream discharge and the height of the
waterfall(Young, 1985). Streams draining plunge pools are usually graded to
both the plunge pool and the trunk stream into which they flow. The height of
thebed of the stream draining the plunge pool controls the average water level
in the pool when discharge levels are sufficiently high. The volume of water in
thepool will of course fall below the level of the bed of the draining stream
when evaporation exceeds that of recharge. During high discharge events the
waterlevel in the plunge pool can rise suddenly causing overbank flows in the
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