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Estuary illegally opened at Breamlea

July 10, 2019 BY

RIGHT: It is not known who illegally dug this trench to open Thompson Creek to the ocean.

GOVERNMENT agencies are investigating the illegal opening of the Thompson Creek estuary at Breamlea.

Corangamite Catchment Management Authority (CMA) estuaries and environmental water officer Hayley Vinden said it appeared a member of the public had dug a trench to attempt to illegally open the estuary to either let the creek’s water subside or to allow sea water to enter the estuary.

“Artificially opening an estuary without undertaking an environmental risk assessment can have a detrimental impact on fish, birds and wildlife.

“Thompson Creek is a closed estuary with low water levels and low catchment inflows. The water has two layers; an oxygen rich freshwater layer on top and an oxygen-poor saline layer on the bottom.

“If an estuary in this condition is artificially opened, the oxygen-rich surface layer flows out first, leaving behind water with critically low oxygen levels.”

In June, a northern NSW council experienced a fish death event after an estuary was opened.

The fish were starved of oxygen as the rapid outflow of water from the estuary reduced oxygen levels.

Consistent winter rainfall combined with a natural sand berm blocking water flows at the mouth of Thompson Creek estuary caused some local flooding, but agencies agreed that an artificial opening was not required in the absence of any significant imminent threat to human life and property and in recognition of the environmental benefits of retaining water in the estuary.

It is an offence to open an estuary if you are not the permit holder. Any person or people found to have contributed to an unauthorised river mouth opening could be prosecuted under section 295 of the Water Act (1989) and could face fines and/or imprisonment.

The main factors used to determine if an artificial estuary opening is required are the protection of built infrastructure or inundation of agricultural and residential land.

Once the decision is made to open an estuary, the Corangamite CMA is notified and undertakes a detailed risk-based assessment to inform the permit holder/s, when and how an estuary can be opened.

The Surf Coast Shire, City of Greater Geelong, Great Ocean Road Coast Committee and Corangamite CMA will continue to monitor the situation.

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