Geoscience Reference
In-Depth Information
A Wave Conditions
7
6
5
4
3
2
1
0
Offshore
Inshore
25
30
1
5
10
15
May
June
B Tide Conditions
Actual
2
Predicted
1
Actual
Predicted
0
25
30
1
5
10
15
May
June
Storms of 25 May-15 June 1974 at Sydney, Australia. A) wave heights B) actual and predicted tide heights (adapted from Bryant & Kidd,
© 1975).
Fig. 3.18
scarping along a face 2 m in height at the rate of
1 m min
-1
. Despite these large rates of retreat, coastal
erosion was highly variable, with some beaches
escaping the storm completely unscathed. Similar
results were found for the Ash Wednesday storm along
the east coast of the United States.
Since 1974, there have been similar east-coast lows
just as intense as the May 1974 storm. The autumn
storms of 1978 and 1985 both produced 10-meter waves
at Newcastle. Historical documents also suggest that
storms rivaling the 1974 storms for intensity have been
common over the past century. The fact that the fre-
quency and magnitude of storms appears to be constant
over time is not unique to New South Wales. A similar
effect has been observed along the east coast of North
America. In the long term, there is no evidence that
storms are solely responsible for coastal erosion in New
South Wales. Additional causes of beach retreat will be
described in more detail in Chapter 8.
A)
Undermining and collapse of beachfront houses at Bilgola
beach, Sydney following the 25 May 1974 storm.
Fig. 3.19
The Sydney Hobart Yacht Race storm of
27-29 December 1998
(Australian Bureau of Meteorology, 2001)
Boxing Day in Sydney heralds the beginning of
the Sydney Hobart Yacht Race that pits amateur and
professional sailors against each other in a leisurely
summer sail down the south-east coast of Australia.
The deadly storm that beset the fleet in 1998 not only
Fig. 3.19
B)
The same storm caused up to 40 m of erosion on other
beaches. The collapsed structure shown here was a
picnic table shelter situated about 5 m shoreward of the
previous dune scarp at Whale Beach, Sydney.
