Processes Impacting on Lake Macquarie

Channel and Water Quality
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The concept of improving water quality in Lake Macquarie through increased tidal flushing has been the subject of numerous investigations over the past decade.

This research has identified a number of reasons that make increasing the size of the Channel opening problematic.

Increasing the size of the channel opening is not only unlikely to result in significant water quality improvements, but there would also be side effects that would have more serious social and environmental implications than the ones it intended to fix.

Many people believe incorrectly that by increasing the tidal flushing of Lake Macquarie, the issue of poor water quality would be solved automatically. However, because the Lake contains such a huge volume of water, increasing the tidal exchange would have little impact on water quality.

Studies have shown that even if the Lake entrance was increased by 20% the impact on the tidal exchange would only be 0.2%.

However, an increased tidal range between high and low tide within the Lake itself would result and this would cause significant problems such as flooding of low-lying areas around the Lake foreshore, increased channel bank erosion, possible destruction of seagrass beds and increased exposure of mud flat areas at low tide.

Any significant opening or enlarging of the Channel will raise flood levels particularly when ocean levels are high. The frequency of flooding in low-lying areas such as Marks Point, Swansea Flats and Belmont South would be increased.

Research has shown that the best way to improve water quality is to stop sediments and nutrients from entering the Lake via stormwater. The best way to achieve this is to restore and mimic natural processes.

Supporting natural filtration systems like wetlands and vegetated areas (especially around creek banks and in drainage lines) is important as they remove contaminants from stormwater to reduce the stress on the Lake.
The Project Management Committee has funded a number of projects to ensure that stormwater entering the Lake does not contain excessive sediments, nutrients and other contaminants. These include the construction of wetlands, sedimentation traps, vegetated drainage swales and foreshore vegetation.

We are starting to see some early signs of improvement in Lake health, although it is a long term task and we still have a long way to go.

 

Editiorials
Channel Challenges
Channel & Water Quality
Constant Change
Seagrass
Seawalls
Threats to the Lake
Vegetated Swales
Water Sensitive Urban Design
Wetlands
Wrack & Ruin
Introduction