Bray Park Weir Tidal Protection Project

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Alert for deployment of barrier to protect weir

There is a continuing risk that Bray Park Weir, which supplies raw water for the Tweed Shire, may be overtopped by tidal salt water during high tide and sea level anomaly events for the foreseeable future. Council monitors this risk and acts to protect the weir when necessary by installing concrete blocks to narrow the weir and temporarily raise the water level in the weir pool. The blocks are removed when the risk has passed. Residents who want to receive an email alert ahead of Council installing concrete blocks to temporarily protect the weir should register their name and email address by emailing wateradmin@tweed.nsw.gov.au (Subject: Weir Alert). Worst-case, Council will provide three hours’ notice of a temporary raising of the weir wall.

About

A combination of high tides plus an unforeseen sea level anomaly caused Bray Park Weir to be overtopped on the nights of the 21 and 22 August 2017.

The overtopping occurred at a time of low flow in the Tweed River and the consequence was salt water ingress into the Bray Park Weir pool.

The salt water ingress caused the raw water provided to the Bray Park Water Treatment Plant to be contaminated. Consequently, the contaminated salt water went into the Tweed drinking water supply.

At no time was it a risk to human health.

This issue will become worse over time with the impact of climate change and subsequent increases in sea levels.

This project seeks to identify and assess a range of options to reduce the risk of salt water ingress into Bray Park Weir both now and into the future and to identify a preferred option for Council’s consideration.

The preferred option may be a engineered or non-engineered solution or mix of solutions.

Alert for deployment of barrier to protect weir

There is a continuing risk that Bray Park Weir, which supplies raw water for the Tweed Shire, may be overtopped by tidal salt water during high tide and sea level anomaly events for the foreseeable future. Council monitors this risk and acts to protect the weir when necessary by installing concrete blocks to narrow the weir and temporarily raise the water level in the weir pool. The blocks are removed when the risk has passed. Residents who want to receive an email alert ahead of Council installing concrete blocks to temporarily protect the weir should register their name and email address by emailing wateradmin@tweed.nsw.gov.au (Subject: Weir Alert). Worst-case, Council will provide three hours’ notice of a temporary raising of the weir wall.

About

A combination of high tides plus an unforeseen sea level anomaly caused Bray Park Weir to be overtopped on the nights of the 21 and 22 August 2017.

The overtopping occurred at a time of low flow in the Tweed River and the consequence was salt water ingress into the Bray Park Weir pool.

The salt water ingress caused the raw water provided to the Bray Park Water Treatment Plant to be contaminated. Consequently, the contaminated salt water went into the Tweed drinking water supply.

At no time was it a risk to human health.

This issue will become worse over time with the impact of climate change and subsequent increases in sea levels.

This project seeks to identify and assess a range of options to reduce the risk of salt water ingress into Bray Park Weir both now and into the future and to identify a preferred option for Council’s consideration.

The preferred option may be a engineered or non-engineered solution or mix of solutions.

Discussions: All (6) Open (4)
  • Criteria a Solution or mix of Solutions must meet

    by BrendaH, about 3 years ago
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    Please add to the Criteria below that you would like a Solution or mix of Solutions to meet. 

    ·  Not permanent

    ·  Deployable in 8 hours

    ·  Durable for flood

    ·  Acceptable TDS or range of acceptable TDS

    ·  Cost effective

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  • Solutions or mix of Solutions

    by BrendaH, about 3 years ago
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    Please nominate Solutions or a mix of Solutions to be considered by the Project Reference Group.


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  • Flood gate operations and the role they serve

    by BrendaH, about 3 years ago
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    I am curious as to the flood gates operations and the role they serve. I’ve always been of the mind set that these gates are in place to prevent salt water feeding back into the cane drains to protected the cane and the soil from the salt, if that is not the case could you please clarify what their roll is please.

    We had meetings with cane farmers and I was fairly sure this was the roll flood gates played for the cane farmers. I would appreciate some clarification on this. 

    Regards Pryce Allsop 


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  • Understanding of the datums

    by BrendaH, about 3 years ago
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    AHD (Australian Height Datum) is also functionally the same as MSL - mean sea level. This is a height datum point = 0m

    However, tides are based on LAT - Lowest Astronomical Tide, which is effectively the lowest tide of the year and this datum is also 0m. (But a different 0m).

    We should never see a low tide with a minus sign. We do, but this is due to meteorological factors like high pressure systems, off shore winds etc.

    Based on the NSW Ocean and River Entrance Tidal levels 2104-2015, the difference between AHD and LAT for the Tweed River is 0.893m

    So if a tide chart shows a high tide at the Tweed River mouth of 2.0m, the water level would be 2.0 - 0.893 = 1.107 AHD.

    I hope this helps.

    Peter Robson

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  • Values

    by BrendaH, about 3 years ago
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    What Values do you want the solution or mix of solutions to this issue to adhere to? 

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  • Measurements

    by BrendaH, about 3 years ago
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    What measurements would you put in place to measure the effectiveness, cost/benefit etc of the solution or mix of solutions? 

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