AbstractOn the New South Wales, Australian east coast there are several estuaries with similar characteristics. Disconcertingly, the construction of training walls and jetties (breakwaters) at four of the medium-to-large sized estuaries have tripped their associated channel and lake (bay) systems from a long-term shoaling mode into an unstable scouring mode (Nielsen and Gordon 1980, 2008, 2017; Couriel et al. 2013. Field data and hydraulic theory confirm that such estuary entrance works have increased the tidal conveyance of entrance channels by modifying channel cross-sections, removing sand bars, extraneous littoral currents and associated sand movements that, previously, impeded ebb tide discharges and ocean tide forcing (Nielsen and Gordon 2017; Escoffier 1940).
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