Processes Impacting on Lake Macquarie

Vegetated Swales
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This is the first instalment of a six-week series that will look at some of the major issues facing the Lake Macquarie environment. Each week I will try to provide an explanation to some of the common questions and sometimes misconceptions that exist about the environmental management of the Lake.

The first issue I have chosen to look at is concrete drainage systems.

  • Why are concrete drainage systems considered harmful to Lake Macquarie?
  • Why is the natural alternative still the best way of managing stormwater run-off?

We traditionally associate urban areas with neatness and tidiness. Over history the existence of concrete kerb and guttering, and drainage lines, has been accepted as a feature that enhances the appearance of the areas in which we live. It's often true that communities who don't have kerb and guttering in their neighbourhoods lobby Council to have it provided.

From an environmental management point-of-view, especially in Lake Macquarie, this insistence on more concrete and less natural vegetation is ironic.

Concrete is obviously a hard, impermeable surface. Stormwater travels across concrete quickly and it does not absorb into the surface. Along the way it picks up soils, oils, pet faeces and other materials that are part and parcel of suburban life. Even though we have developed engineering solutions to try to filter stormwater, concrete systems mean that stormwater reaches the Lake at greater speed and in greater volumes.

The natural system is quite different. Vegetated drainage lines are very effective at absorbing stormwater into the soil, decreasing the volume and slowing the speed at which the water travels into our waterways. The vegetation also acts as a natural filter, removing sediments and nutrients as well as increasing the oxygen level in the stormwater, so that it reaches the Lake in a much cleaner and healthier condition.

As we learn more about natural systems and the responsibilities we assume by living on the edge of major waterways, we are experiencing a major shift in thinking about how we develop our urban areas.

In some areas we are now removing concrete drainage lines and replacing them with carefully designed 'natural' systems. This is not a complete about-face back to the days of primitive natural earth drainage lines, but a modern compromise that aims to balance infrastructure needs with responsible environmental management.

The Office of the Lake Macquarie & Catchment Coordinator does acknowledge that swales are not suitable for all locations, such as flat or low-lying areas prone to flooding and where there is high-density development that requires hard engineering solutions to cope with highly concentrated volumes of stormwater. We will continue to develop innovative solutions that use natural systems where possible to manage our impacts on the Lake.

 

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