The evolution of Jumpinpin Inlet - OzCoasts

The evolution of Jumpinpin Inlet
Stradbroke. A local fisherman, Mr Greg Litherland (pers. comm. 1997), recalls the
channel being very deep at this time. After regaining some of its width the channel
returned to discharging flow in a northerly direction. The result was rounding of the
base of North Stradbroke and further development of a downdrift offset.
From 1983 to 1987 South Stradbroke grew in the usual manner with few severe
cyclones to impede growth. Correspondingly, the northern channel widened by
preferentially scouring the downdrift bank. Interestingly, the rate of sand deposition
was slower in this period than during the 1950s, even though several cyclones
affected Jumpinpin in the 1950s. In 1985 work on the seaway began and it was
expected that increased capture of tidal prism there would accelerate the rate of
closure of Jumpinpin. By 1993 the southern channel had closed off all together, after
which channel migration took place.
Throughout the last 50-year period sand was lost from the system in two ways: firstly,
by dune building on the back beach of North Stradbroke; and secondly, by aeolian
and tidal infilling of Swan Bay. It is conceivable that during floods some sediment may
have been moved to deep water from which it could not be readily returned. Infilling of
Swan Bay accelerated with westward migration of the updrift bank.
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