Standby as tides may flush creek mouth
Council has been sampling the water quality in Mooball Creek for the past week to monitor the effects of the creek mouth being blocked with sand due to limited tidal flushing.
To date, the water meets safe levels for the protection of aquatic ecosystems and swimming.
“Water in the creek is becoming a little greener,” Council Waterways Program Leader Tom Alletson said. “This is due to the growth of phytoplankton (single-celled, non-toxic green algae), which is building up due to reduced tidal flushing. This is natural and typical of water quality further up the creek where tidal flushing is always more limited.”
The creek has become blocked due to: a very large beach width to the south of the creek mouth’s rock training walls; and, the formation of a sand bar east of and across the creek mouth.
The mouths of a number of other creeks in the Tweed are undergoing similar conditions, including both Cudgera and Cudgen creeks. None of these, however, have become blocked.
The high tides and south swell forecast for last weekend may improve conditions at the mouth of the creek.
Council will continue to monitor the situation to determine if it needs to intervene and clear the blockage but any channel dug artificially to allow the creek to drain could be closed again by the next tide dumping more sand.
“If we can let nature do the job for us, we will achieve a better outcome,” Mr Alletson said.
“We may see beach and entrance sand bar conditions like this persist for several weeks or more, and we can’t open the creek every day, so caution, monitoring and preparedness must be the approach.”
Mooball Creek last became blocked in 2007.
“Prior to the construction of training walls and floodplain drains, the systems would have spent a much greater proportion of time separated from the ocean. The aquatic ecosystems adapt to it, but the difference these days is water quality. Runoff from the catchment, including both urban and agricultural development, means we need to ensure that levels of dissolved oxygen do not fall so low that aquatic fauna is at risk, or that bacteria levels do not climb so high that swimming conditions become unsafe.”