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Lack of rigour risks the mighty Maroochy



11 August 2017

Too Many Unanswered Questions Risk the Mighty Maroochy-SCEC

The Sunshine Coast Environment Council is questioning how Council’s own fact sheet[1]  can identify a 200 metre rock groyne as the “most beneficial option” to replace the existing sand groynes in Maroochy estuary, while the supporting engineering studies (JBP Maroochy Groynes CBA Final Report (6) Summary) admit that this is based on an “early conceptual design only”.   The study admits that the use of single terminal groynes has widely documented positive and negative effects, the latter notably including reduced sand supply to northern beaches.

Spokesperson Narelle McCarthy said the Gold Coast has a well- documented history that we would do well to learn from.

“Initially rock walls were built to “train” the Tweed River in the late 1960s.  Over time this has led to longer rock walls being built and a series of groynes along beaches to the north with perpetual sand pumping to maintain Gold Coast beaches. Interference with nature at a dynamic river mouth such as the Maroochy has consequences that are likely to cost a lot more in the long run.”

“The report and apparently Council’s preferred option involves removing the sand groynes that have protected Cotton Tree so well for the past decade and provided a safe well used family beach.  The consultants admit a 200m long rock groyne will introduce a new dynamic into the estuary with unknown consequences, but that additional maintenance costs to protect the holiday park would be required. Wasn’t that why the groynes were put there in the first place? All options involve continued sand nourishment of Maroochydore beach.”

This has been supported by Trevor Lloyd, one of Queensland’s most experienced environmental consultants, who helped establish Southeast Queensland’s Healthy Waterways Program in the 1990’s, and who has authored a major study of the coastal geomorphological effects of hard rock training walls constructed at the Tweed River mouth in the mid-1980’s. His study showed how the construction of the rock walls had led to massive downstream erosion of a number of the Gold Coast’s key tourist beaches which subsequently required very expensive artificial sand by-pass pumping systems to rectify.

Mr Lloyd noted that the cost-benefit report prepared for Council actually stated that the preferred hard rock groyne option was subject to the caveat that “In order to remain the most cost-beneficial, a position and orientation would need to be identified that offered protection to the Cotton Tree beach, minimised annual nourishment costs, did not incur other damages such as downdrift erosion, and did not significantly change the structure dimensions, and therefore costs”.  Mr Lloyd also noted that the report appeared to include not a single reference to any of the myriad of technical reports and papers prepared on the subject of eastern Australian beach erosion over five decades of investigation and research.”

Ms McCarthy described the two options to permanently train the river to the northern channel as “an expensive waste of time to evaluate as they would be highly unlikely to gain State approvals” and urged people to attend the community information sessions to ask questions.

“Even though these sessions are disappointingly described by Council as information sessions rather than being proper community consultation, it is imperative people attend to share their views” she said.

“This is a decision that should not be made on the basis of an economic cost benefit analysis alone and we look forward to a similarly detailed study of the environmental benefits. For instance, removal of large amounts of sand in the estuary would cause enormous damage to fish breeding cycles.” Ms McCarthy concluded.


[1] Maroochy Groyne Field Community Consultation

See here for further information and Council’s community information session details