A $2.3 million project to dredge the Woolston Cut of silt and liquefaction will be done so it continues to provide effective flood remediation.
City council land drainage manager Keith Davison said the cut was about 50 per cent full of silt and liquefaction.
But he said that did not impact how it operated during the recent flooding that began on July 21.
“For this to continue to operate effectively it is necessary to maintain capacity by dredging from time to time,” Mr Davison said.
The cut was built in the 1980s to prevent flooding in the lower Heathcote River area, and for other catchment-wide improvements, such as the upper Heathcote detention basins.
Water from the Heathcote flows into the cut, which can then be opened during floods using the tidal barrage.
Mr Davison said it had never been dredged.
He said the recent flooding was unlikely to have an impact on the project timings and costs.
“The flooding does highlight to everyone how important it is to have an effective and fully operational land drainage and stormwater network and it is important that the cut and barrage remain operational.”
He said the tidal barrage would have helped flood protection by opening and providing additional downstream capacity.
“As I understand it the current silt levels in the cut will not have impacted upon flooding as the original design always envisaged and allowed for reasonable levels of silt build-up,” he said.
“Having said this, current silt levels have now reached a point where it would be good practice to dredge as further build-up could start to begin to risk impacting upon operation.”
He said city council staff were now seeking funding approval for the project.
If it was granted for the current financial year, the work could start in October, he said.
As part of the project, the footpath earthquake repairs at Staunton Esplanade Reserve would be delayed, as heavy machinery would need to go through.
The footpath repairs are likely to take place early next year.