Super storm cell tested Coffs Harbour's flood proofing
COFFS Harbour recorded the state's largest rainfall figures during the weekend's supercell storm, yet the city's flood proofing measures stood up to the test.
As the storm front caused destruction in Woodburn, rain gauges overflowed on the Coffs Coast.
The Bureau of Meteorology said the official Coffs Harbour gauge collected 160mm in the 24 hours to 9am Sunday - the heaviest rainfall recorded across NSW.
The deluge caused minor flooding in Bray St and over the Pacific Highway in Coffs Harbour South while stormwater drains also backed up in the city centre.
The large rain band also centred over Woolgoolga, Urunga, Nambucca Heads, Dorrigo and Bellingen and residents across the region have reported localised falls of up to 200mm in some areas.
At the height of Saturday night's falls, Coffs Harbour City Council staff and State Emergency Services monitored creek levels after the city's flood early warning system was activated.
It was noted how the Baker's Rd detention basin - built after the floods of 2009 - helped to hold back floodwaters in Coffs Creek.
"In terms of the storm event itself, it was relatively minor in comparison to 2009," said Coffs Harbour City Council's Director of City Services Ben Lawson.
"As you say the BOM reported 160mm in 24 hours, whereas the March 2009 event saw around 400mm, two and a half times the water, fall within a similar time period.
State Emergency Services Coffs Harbour Unit Controller Bill Roffey said the intensity of the rain was similar to the falls, which flooded the city in 2009, but fortunately the downpours abated.
"It looked just like it did in March 2009 when the heavens opened," Mr Roffey said.
He said the southside of the city from Combine St down to Boambee and Toormina was hardest hit just after 6.30pm with torrential rain also falling around Perry Dr, Shephards Ln and over Red Hill.
As the flood early warning system was activated information on floodwater levels in the catchment were transmitted in real time back to a central monitoring system observed by the SES, BOM and council staff.
Mr Lawson said there are currently nine monitoring sites in the Coffs Harbour catchment, two of which monitor rainfall and seven which monitor both rainfall and water levels.
"Primarily these sites are in the Coffs Creek catchment, however there are monitors in both Middle Creek (Sawtell) and Newports Creek catchments as well," Mr Lawson said.
"Currently, alarms are sent to council staff when certain trigger levels, either rainfall intensity or water level are reached, and equipment will soon be installed to enable alarms to be sent to SES as well.
He said the Baker's Rd detention basin fared well during the downpour.
"The storm event was well within it's capacity and it detailed the flows in Coffs Creek, reducing water levels down stream, which in a larger event can be as much as 0.2 metres.
The council plans to finish the Bennett's Rd basin early next year to further reduce flood levels in Coffs Creek by up to an additional 0.14m downstream.
Final planning and approvals are also underway for the Upper Shephards Ln and Spagnolos Rd basins.