Standby as tides may flush creek mouth

Tweed Daily News - - NEWS -

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.”

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