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600
500
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100
0
1640
1680
1720
1760
1840
1880
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Year AD
Figure 3.11.
Coral luminescent line record of flood discharges from the Burdekin
River, North Queensland, Australia (data from Isdale
et al.
,
1998
).
0
=
no visible line, 1
=
faint luminescent line, 2
=
moderate luminescent line
and 3
=
intense luminescent line. Reefs were divided into three groups: those
that never recorded run-off, those that recorded run-off but not every year and
those that recorded run-off every year. Lough
et al
.(2002)foundthattheaverage
intensity of the luminescent lines was inversely related to the distance of the
coral reef from shore and also to the average water depth between a reef and
the mainland. They also found that annual variations in luminescence intensity
were significantly correlated with instrumental measurements of annual river
flow. This suggests that, on the Great Barrier Reef at least, luminescence lines
are a reliable proxy of river discharge.
Figure 3.11 shows a 350 year record of luminescent lines from corals experi-
encing the flood plume from the Burdekin River, North Queensland. It is inter-
esting to note that this annual record shows periods of relative quiescence in
flood discharges between approximately AD 1770 and 1870, and the period from
AD 1640 to 1770 was dominated by many more high discharge events than during
any other century over the sampled time period. Except for the period around
AD 1880 to 1910, flood discharges up to present have been relatively low for over
two centuries. Such a record highlights the concept of hazard or event regimes
and emphasises the need to check for non-stationarity when undertaking risk
assessments. In this case, non-stationarity is clearly evident in this prehistoric
record.
The largest known floods on Earth
10
7
m
3
s
−
1
occurred during the late Pleistocene when ice dammed lakes burst releasing
High energy megafloods with discharges as great as 1
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