Geoscience Reference
In-Depth Information
Because of localized decreases in river depth and
higher flood heights, over 1300 km of main levees had
to be raised after the 1973 flood.
As of 1993, the total damage caused by Mississippi
flooding was equivalent to $US4.4 billion. The Great
Flood of 1993 was worse (Figure 6.11). Mobile polar
highs were stronger than normal in the spring of 1993,
dragging cold air south into contact with warm air from
the Gulf of Mexico. By April, the biggest floods on
record were sequentially swamping the Missouri-Missi-
ssippi floodplain from north to south. The pressure
patterns continued into summer with rainfalls exceeding
200-350 per cent of the norm. Flood levels reached
75-300-year recurrence intervals along major portions
of the upper Mississippi and lower Missouri Rivers. On
1 August, the Mississippi crested at 15.1 m at St. Louis,
2.0 m above the previous record. Transport across the
Mississippi for a distance of 1000 km was interrupted,
1000 levees collapsed, 55 people lost their lives, 48 000
homes in 75 towns were flooded, and 74 000 people
were left homeless. The total damage bill across 12
states was $US18 billion. Fortunately, modelling
forecast the disaster four months in advance, giving
plenty of time for preparations and evacuation.
Gre
at Australian floods
(McKay, 1979; Shields, 1979; Holthouse, 1986; Yeo,
2002; Australian Bureau of Meteorology 2003a, b)
The major rivers of eastern Australia originate within
the Great Dividing Range, which parallels the east
coast (Figure 6.13). Two systems flow westward.
The Murray-Darling system and its tributaries - the
Warrego, Condamine, Macintyre, Macquarie, Lachlan
and Murrumbidgee - forms the largest river system
in Australia, entering the southern ocean south of
Adelaide. The other system consists of the Diaman-
tina-Coopers Creek rivers, which flow into landlocked
Lake Eyre. On the eastern side of the Dividing Range
are a number of much shorter, but just as impressive,
systems. These rivers consist of the Hunter, Macleay,
Clarence, Brisbane, Burnett, Fitzroy, and Burdekin.
Successive tropical cyclones or monsoonal troughs
have in the past severely flooded all of these rivers, but
never at the same time. Aboriginal legends from the
Dreamtime imply that many river valleys have been
flooded over widths of 50 km or more. Three flood
events: the wet of 1973-1974, the Charleville-Nyngan
floods of 1990 and the Katherine floods of 1998 - all
Daly
Gulf of
Carpentaria
Katherine
Coral Sea
Mitchell
Leichhardt
Northern
Territory
Burdekin
Gilbert
Queensland
Flinders
Alice Springs
Fitzroy
Diamantina
Burnett
Charleville
Finke
Condamine
Coopers
Cr.
Brisbane R.
Brisbane
Macintyre
Warrego
Clarence
Lake Eyre
Nyngan
South Australia
Darling
Macleay
Macquarie
Wentworth
Hunter
Lachlan
NSW
Murray
Sydney
Murrumbidgee
Southern Ocean
Gippsland
Victoria
Tasman
Sea
0
1000 km
Major rivers of eastern Australia.
Fig. 6.13
