Clarrie Hall Dam not for flood mitigation

Tweed Shire Council

Tweed Shire Council has adopted a policy that clarifies when and how Council releases water from Clarrie Hall Dam.

The policy was adopted by Council at its meeting on 27 October 2022.

Water and Wastewater operations manager Brie Jowett said the Clarrie Hall Dam Water Release Policy was developed in consultation with the community and thanked residents for submitting feedback.

“The dam is built with an open, un-gated spillway. It is designed for storing drinking water, not to mitigate against flooding,” Mrs Jowett said.

“Tweed Shire Council does not manage the reservoir level by pre-releasing water ahead of rainfall events to provide any form of storage capacity for flood-mitigation purposes.

“The policy clarifies that Council cannot control water that spills from the dam once the water level in the dam reaches the spillway crest.

“When the dam fills during intense rainfall events, it is designed to safely pass the excess water into Doon Doon Creek and then the Tweed River. This spilling cannot be controlled.”

Mrs Jowett said the dam’s size and location meant any upgrade would not alter its purpose.

“We live in one of the highest rainfall areas on the east coast of the nation, which has eroded the Tweed caldera over millions of years and carved out the natural beauty that is the Tweed Valley,” she said.

“We must acknowledge the dam’s catchment takes in less than 6% of the overall catchment area of the Tweed River and its upstream creeks and rivers.

“To have any impact on mitigating flooding, a drastically bigger dam would be needed. However, the proposed Clarrie Hall Dam upgrade for water supply purposes is the maximum feasible size for a dam at this location.”

Mrs Jowett added one dam would offer little protection.

“We would need several very large dams to capture rainfall that feeds the Tweed, Oxley and Rous Rivers,” she said.

“Previous flood studies have shown large dams at those locations would not be practical.”

Access the policy from tweed.nsw.gov.au/policies. Head to tweed.nsw.gov.au/clarrie-hall-dam to find out more about Clarrie Hall Dam.

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