The Eurobodalla Coast Alliance (ECA) is pleased to release the Sethi report on the “Erosion of Batemans Bay’s Northern Beaches”.
This long awaited report clearly identifies the cause of the erosion that destroyed the old Wharf Road subdivision and unsurprisingly, most of the evidence has been compiled from Council’s own reports. Contrary to popular belief, the erosion is directly attributable to engineering works conducted on the southern side of the Bay and Clyde River estuary. The report and the findings have been endorsed by Angus Jackson, the principal of International Coastal Management, and one of Australia’s most respected coastal engineers.
The author Viv Sethi is a retired engineer, and foundation member of the ECA. Viv is a resident of Surfside, a suburb that is now severely exposed to coastal storm events as a result of erosion of the northern sand shoal.
The ECA encourages Council and the NSW State Government to take note of the findings in this report, and to take action to reclaim/reinstate the Wharf Road subdivision and develop an engineering solution to replace the sand shoals that once protected the northern suburbs from severe weather conditions.
Northern Bay beaches need Government repair - report
A new report has found erosion of north Batemans Bay beaches was caused by public works rather than natural forces, opening up a call for the State Government to fund mitigation measures as a matter of urgency.
The report also warns that the design of the proposed new Batemans Bay bridge could compound the problem and calls for an immediate risk assessment of the impact of the project on bay foreshores.
The report was commissioned by lobby group Eurobodalla Coast Alliance and was prepared by Surfside engineer Viv Sethi. The report has been endorsed by 'world renowned' coastal engineer Angus Jackson
It is part of a broader Alliance concern about State and local government management of “coastal hazards”. Thousands of Eurobodalla properties are likely affected by these plans.
ECA President Russell Schneider said the Alliance had decided to focus first on the north shore erosion issue because of the potential threat to northern properties if a severe storm suddenly hi5t the district.
Mr Schneider said the report opens the way for Eurobodalla Shire Council to seek State Government assistance to deal with the north shore erosion problems and save properties. It establishes that the problem came about because of human intervention in the environment.
Mr Sethi’s report states that various public works on the Bay’s foreshores had resulted in a massive sand build up- more than 800,000 cubic metres- on the south side of the bay, most notably at Corrigan’s Beach, which has been extensively reclaimed as a result.
“It is also apparent that the protection afforded the Northern Beaches of the Inner Bay by the Sand Spit and Shoal is no longer there, leaving these beaches exposed to the prevailing storms from the South East.” Mr Sethi said.
“The analyses presented indicate a strong correlation between Public Works carried out on the Clyde River and the build up of Corrigans Beach. There is also a strong correlation with the erosion of the Northern Sand Spit and Shoal,” his report states.
“The most accurately documented record of the Public Works carried out was the 150m extension of the break wall in 1988-1991 This extension caused Corrigans Beach to accrete 150m in 3 years with erosion of Surfside beach being experienced immediately.
“The building of the bridge in 1956 and the resulting effect of its pylons on river flow went largely unnoticed until the river was in flood, whereby the sudden channel width expansion also caused high velocity eddy currents downstream of the highway bridge .The damage caused to the Northern Beaches, in particular Wharf Road, by the 1974 ‘Super Storm’ could likely have been exacerbated by the artificial erosion of the Northern Sand Spit and Shoal and compounded by the constriction of flow caused by the Bridge Pylons.
The damage sustained by the Inner Beaches during the 1974 ‘superstorm’ occurred at time when the Northern Sand Spit and Shoal still offered them some protection, even though they had been partially eroded. However that protection is now largely non-existent in comparison, and a storm of equal magnitude to the 1974 storm would cause considerably more damage. Given that the 1974 storm was considered a "one in a hundred-year‟ event and that it has been 43 years since then, it is recommended that this needs to be addressed as a matter of urgency and mitigation measures taken immediately.
The findings of this report necessitate that a thorough study to verify the cause of the erosion of the Northern Sand Spit and Shoal needs to be undertaken prior to properties being identified as vulnerable to ‘coastal hazards’ because the hazard appears, in fact, to be the result of Public Works on the other side of the river. The seemingly incorrect assumption made by the reports analyzed was that the accretion of Corrigans Beach and the erosion of the Northern side happened slowly and imperceptibly over nearly 100 years. As identified in this report, the accretion of Corrigans Beach and corresponding erosion of the northern side has occurred in "spurts‟ that are closely correlated with Public works carried out in the Clyde River. In addition, this report did not analyze the effects of the dredging operations that have been carried out because of a lack of information regarding the dates, quantities removed or location of where the dredged material was taken. All that is known about the dredging is that the dredged sand has “repeatedly been placed at the northern and centre thirds of Corrigans Beach over many years” and this has, no doubt, increased the erosion of the Northern side.
Media release authorised by Russell Schneider President ECA January 24 2018
. Post Script: Editor: Before anyone is stupid enough to venture into defaming this report and its author might I suggest that you read this letter of peer review by Angus Jackson (made available with permission) - for full document http://bit.ly/2DJohaq