Following the recent flooding of the Macleay River, it's a good time to explain how some of the flood infrastructure is managed in the Lower Macleay.
The Lower Macleay Flood Mitigation Scheme was built over a 20-year period following devastating flooding in the mid-twentieth century. The flood gates are a critical part of the scheme and are designed to control water flow during a flood event, reducing the impact of floods rather than preventing them entirely.
Key structures are located at Kinchela Creek and Belmore River. There are two types of gates here: flood gates (also known as crossover flood gates) and flood relief gates, each with distinct functions.
Under normal conditions, the gates remain open, allowing tidal movements and aerating waterways. The crossover flood gates span across the waterways, while the relief gates are positioned to the side.
Operating flood gates is never left to chance and guesswork. Highly qualified and experienced staff members make decisions about when to open and close flood gates based on protocols developed over many decades.
Before a flood, Council staff close both sets of gates to prevent water from flowing upstream in the two smaller waterways. This holds floodwaters within the Macleay River and directs water out to the ocean at South West Rocks, protecting the floodplain and agricultural land. This is most effective in minor flooding and reduces impacts from larger events as much as possible.
If the river reaches the levee's height (in line with the roads) on Belmore River and Kinchela Creek, the relief gates are reopened. This creates a controlled water release into the floodplain, aiming to lower flood levels and prevent overtopping the levee system at Belmore River, Kinchela Creek and surrounding communities, reducing the damage to roads, residences and other infrastructure.
The water level in the broader floodplain determines whether the Ryans Cut and Big Hill ocean outlets can be opened. These outlets rely on upstream water pressure from the floodplain to operate. Pilot channels are created to guide water to the ocean, gradually increasing the flow to allow all gates to release floodwater. However, if the floodplain lacks sufficient water, the ocean will close the gates and prevent waterflow.
Council staff communicate directly with residents and landowners near flood and relief gates to help them prepare.
Additional information of Council's flood mitigation can be found at ksc.pub/flood-info
