Locals start to get the drift
THE angst over the possibility of huge amounts of silt being dumped at an enlarged version of the current Cairns port dump site – which is slightly north of Cairns and about 15 km out to sea – has been heightened by a report by Sinclair Knight Merz, commissioned by GBRMPA and filed last June.
It is significant because, as Dr Eric Wolanski, independent reviewer to the GBRMPA stated, ‘‘for probably the first time in the history of modelling the fate of dredged sediment in the GBR, the authors did model the long-term fate of fine sediment after initial settling near the dump sites, ie, they attempted to answer the question where does the sediment ultimately go?’’
The difference is that the currents have been called into the modelling. The SKM papers say that ‘‘the use of large-scale currents has highlighted that dredge material may travel longer distances, through constant resuspension from the material placement site than previously appreciated’’.
The modelling shows wind and current patterns could help dredge material ‘‘drift’’ to the north-north west from where it is dumped.
Their modelling looked at various scenarios using the current dump site off Cairns and two more theoretical ones – Model Case 1, 20 km north-north-east of Cairns port in 18m deep water; and Model Case 2, 32 km north-northeast of the port in 18 metres (laterally, out to sea off Rex Lookout).
In the various scenarios sediment was expected to have been found in waters around Low Isles and all the way to Point Kimberley, to some degree or other.
Discussion of this at the Douglas LMAC meeting last Thursday was ‘‘robust’’, according to chairperson Robert Hanan.
GBRMPA director Dr Adam Smith attended the meeting. He explained the Abbot Pt decision by GBRMPA, and subsequently the issue of the Trinity Inlet dredging came up. Local tourism operators who are on the Douglas LMAC expressed consternation at the latest studies on possible sediment drift from the Cairns project. Others remarked that a goahead with more maritime dumping ‘‘makes a mockery’’ of all the pollution mitigation work that local farmers have done, and the work of the school reef guardians.