The evolution of Jumpinpin Inlet - OzCoasts

The evolution of Jumpinpin Inlet
Figure 5.1. The four shapes of barrier island inlets
(Source: SPM, 1984)
Jumpinpin is seen to exhibit characteristics of a slight to negligible downdrift offset
which would result from equal wave approach on both sides (SPM, 1984). Yet, where
moderate gross rates of littoral drift are associated with a strong rate of net drift, as is
the case at Jumpinpin (C.O.P.E, 1985), the situation favours an updrift offset. The
lack of such an offset must be due to local processes which this study aims to identify.
5.4 Channel size and delta formations
The main channel at Jumpinpin had a width of around 775 metres at its widest
point in 1993. The throat at this time was about 1.5 km long and discharged in a
northeasterly direction. When newly breached, the smaller channel (to the south
of the main channel) averaged a width and throat length of 900 and 1500 metres,
respectively.
On microtidal, wave-dominated coasts, Hayes (1991) has found that inlets are widely
spaced and have large flood-tidal deltas. Much like a river delta, tidal deltas are
simply deposits of sediment that have been flushed into or out of an inlet (Kana,
1989). A tidal delta comprises a network of sand shoals and channels constantly
undergoing change. The inlets of Moreton Bay are widely spaced; however, there
is a distinct lack of flood delta formation at Jumpinpin. This may indicate either:
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