The evolution of Jumpinpin Inlet - OzCoasts

The evolution of Jumpinpin Inlet
Overall:
• The primary channel has widened by about 350 metres. Of this, 75 metres is
a result of erosion on the updrift bank and the
remaining 275 metres is from retreat of the downdrift bank. From
this comparison, the channel has widened and not migrated.
• The southern channel present in 1944 is closed in 1993.
• North Stradbroke Island has moved east, South Stradbroke spit
has shifted west. The result is an obvious downdrift offset.
• Swan Bay has reduced in size due to widening of the northern channel,
aeolian influence from the east and tidal infilling from
the south.
• Short Island retreated westward.
8.3 Cyclic changes
8.3.1 Comparison of 1944 to 1978
The aerial photograph of 1944 has been compared to 1978 (Figure 8.3) as they show
Jumpinpin in similar stages of evolution. So similar are they that taken on face value it
is hard to believe Jumpinpin experienced some of the dramatic changes shown in
Figure 8.1. In 1944 and again in 1978, two channels were active at Jumpinpin. At both
times the channels show similar widths.
The most noted changes observed between the 1944 and 1978 aerial photographs
are:
• The northern channel is located about 275 metres north in 1978.
• North Stradbroke has moved to the east.
• The recurved spit of South Stradbroke has shifted west.
• The entrance to Swan Bay has moved north and west. The eastern rim
infilled.
42