Major Lake Cathie updates included in monthly waterway management report

THE latest Port Macquarie-Hastings Council report reveals significant updates on the natural resource management of Lake Cathie, Lake Innes, and Cathie Creek, outlining a range of ongoing projects and initiatives aimed at improving the waterways.

A comprehensive 212-page document, the ‘Lake Cathie-Lake Innes Hydrodynamic Model Upgrade Report’, has been finalised.

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This report provides detailed analysis of water levels, tidal gauging, water quality, and sediment conditions.

The findings are set to guide future projects, including coastal hazard assessments and water quality improvement strategies.

Key among the community interests is the report’s modelling assessment of several management strategies: disconnecting Lake Innes from Cathie Creek, widening bridge structures, and establishing a permanent entrance.

For disconnecting Lake Innes, the report examines various environmental conditions.

In a tide-dominated scenario, Lake Innes would experience reduced tidal influence and lowered salinity due to rainfall, while downstream areas would see increased tidal range and salinity fluctuations.

A closed entrance scenario would lead to quicker water level rises with minimal water quality changes.

Sea level rise is expected to amplify tidal range in the estuary, and coastal flooding would protect Lake Innes from coastal inundation, increasing peak water levels in the estuary.

The report also analyses the impacts of widening Kenwood Drive Bridge and Ocean Drive Bridge.

Under tide-dominated conditions, changes in tidal discharge and flushing times are reportedly minimal, with negligible effects on water quality.

Similarly, with a closed entrance, there are negligible changes in both hydrodynamics and water quality.

The scenarios considering sea level rise and coastal flooding show minor increases in tidal range and peak water levels, though water quality impacts are not modelled.

Maintaining a permanently open entrance under different scenarios is also examined.

In tide-dominated conditions, there would be a substantial increase in tidal discharge and range, with the most significant changes near the entrance, resulting in minor differences in salinity, dissolved oxygen, and nutrients.

Sea level rise would significantly increase tidal range, especially during ebb tides.

Coastal flood scenarios would reduce peak water levels due to decreased wave setup.

Water quality impacts were not modelled for sea level rise and coastal flood scenarios.

Greg Suendermann, spokesperson for Revive Lake Cathie, told News Of The Area, “The report adds merit to the disconnection of Lake Innes and Cathie Creek, which Revive Lake Cathie strongly supports.

“We want the actions outlined in this report to move forward quickly, with necessary consultation with key stakeholders and education and information for the community.”

This comprehensive report was set to be discussed at the June 20 meeting of Port Macquarie-Hastings Council, spearheaded by councillor Danielle Maltman.


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