The evolution of Jumpinpin Inlet - OzCoasts

The evolution of Jumpinpin Inlet
Plate 1. Photograph of Jumpinpin taken just prior to the breakthrough,
dated 1896 (Source: University of Queensland Archives)
Detonation of the dynamite from the Cambus Wallace may well be responsible for
creating a weak point for the ocean to breach during severe weather. Welsby notes
that: “Within two years (1896) the southeast gales threw again their power and fury on
the very spot whereat the “Cambus Wallace” had come to grief, drove the rollers and
breakers against the sandy hillside until it conquered and made passage into Swan
Bay” (Thomson, 1967a, pp. 370–371). (Swan Bay must have been the name of the
general area inside the isthmus.) Once the entrance had been made, the rolling surf
on the beach added its weight even in calmer weather and the waters and tides
poured in and out, day after day, enlarging and widening the opening.
Other authors to date the breakthrough at 1896 are Durbidge and Covacevich (1981)
and Kelley (1984).
Dr John O’Hanlon (pers. comm., 1997) believes the breakthrough is related to
clearing of vegetation across southeast Queensland throughout the 1800s.
Widespread clearing increased the potential for flooding and raised flood levels to
higher than equivalent floods before. He believes flood flow placed pressure on the
western side of Jumpinpin and facilitated erosion there.
In his first volume, Welsby contradicts earlier work by stating that: “The break at
Jumpinpin occurred in May, 1898, the first official reporting being under date 13 May,
coming from Mr Andrew Graham, Government official, Southport” (Thomson, 1967a,
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