Flood Mitigation in the Coffs Harbour LGA

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Flood Mitigation in the Coffs Harbour LGA

​​​The Great Dividing Range passes very close to the coast in the Coffs Harbour local government area. With the proximity of the coastal ranges to the ocean, the coastal plain has no major river systems, but there are numerous small creek systems. Overall there are 16 major coastal creeks plus the inland waterways of the Bobo River, Little Nymboida River, Bucca Creek and Orara River. 

Map of waterways & catchments in Coffs Harbour (1MB)

Climate & Rainfall

Coffs Harbour experiences a moderate climate, which has been classified as humid sub-tropical. This is characterised by warm to hot summers and mild winters. The area experiences a high rainfall, averaging 1700mm annually, with most rain falling in late summer and early autumn. The cooler months receive much less rainfall, and dry spells are not uncommon from April to October.
 
Landform has a strong influence on rainfall within the area. Higher rainfall occurs east of the coastal range, due to moist maritime air rising over the land, and can lead to high intensity storms.

Because the catchments are steep, relatively small in area and subject to high rainfall intensities, they experience what is termed 'flash flooding'.

​Flash flooding is:

  • flooding that peaks within six hours of the rain that caused it;
  • very sudden, with little warning of its coming;
  • a result of local heavy rainfall;
  • characterised by rapid rises of stream levels with elevated levels experienced for short periods of time.

Flood Mitigation Programme

Council has made its Flood Mitigation Programme a priority. It includes four flood detention basins.

The Programme was forecast to cost $12m. The funds were secured through a $6m loan and a special rate variation that raised $6m in total.

Detention Basins' Current Status

Bakers Road Detention Basin

The largest of the detention basins was completed at William Sharpe Drive, West Coffs, in 2010. 

Bennetts Road Detention Basin

The Bennetts Road basin construction is fully operational.  A flood warning station and water level recorder were also installed.

Spagnolos Road Detention Basin

The basin was officially opened in March 2015.

Upper Shephards Lane Basin

The land for this basin has been purchased in accordance with Council's resolution of 11 October 2012. Council received notification of a $2.2m grant from the Australian Government in August 2017 to supplement Council funds needed for a detailed design and investigation for the construction of the basin.

Flood Warning System​

Rain gauges and water level recorders have been installed at key locations and are operational. The recording and radio communication systems are fully operational and linked to the Bureau of Meteorology and State Emergency Services which have provided very positive feedback regarding the assistance this provides emergency services.

History of Flooding in Coffs Harbour

There is a long history of flooding in the Coffs Harbour LGA. Significant flood events have occurred in 1917, 1938, 1950, 1963, 1974, 1977, 1989, 1991 and 2009.

In November 1996, a natural disaster was declared when Coffs Harbour experienced major flash flooding with some 800 properties flood affected. The 1996 storm event caused inundation above floor level of over 250 residential properties and 210 commercial or public properties. 300 people were evacuated.

In 2009, a storm on 31 March saw Coffs Creek peak at 5.14m resulting in flash flooding in the Coffs Harbour CBD and surrounding streets.

On 5 November 2009, another major storm saw more than 500mm of rain fall within 48 hours,​ resulting in further flash flooding in the city centre area.