Flood-risk mapping across the Wollongong local government area could be in for a shake-up with a long-overdue review of the council's culvert blockage policy under way.
The Mercury can reveal Wollongong City Council's controversial blockage policy is being reviewed following months of criticism it unfairly skews flood-risk mapping.
It is a major victory for residents who have worked hard to draw attention to the problem.
If the policy is changed, it could lead to relief from skyrocketing insurance bills and over-the-top building restrictions that burden home owners in affected areas.
Residents from Figtree to Thirroul are hoping for some relief from the effects of the blockage policy, and it is largely the work of the Figtree residents' group that has forced Wollongong City Council to re-evaluate whether its flood management plan is fair.
The council this week said it would set up a review of the Allans Creek catchment flood plan, to consider a detailed submission from Figtree's Northview Estate Flooding Residents Action Group (NEFRAG).
The group's John Mathieson said it was the result of many months of working with council officers in a constructive dialogue.
"I think all of our members were pretty happy that we went to the trouble of preparing a pretty decent submission ... and I think it's been pretty well received," he said.
The council announcement followed months of investigations by the Mercury into whether Wollongong has dealt with its flood risks adequately and fairly, in a series under the title Going Under.
On Wednesday afternoon, the council's stormwater services manager Peter Nunn confirmed the Allans Creek review would include a re-evaluation of the blockage policy.
The controversial policy, and the data it was based on, will be reviewed for the whole city.
"Reviewing that historical data and analysis and redetermining a new blockage policy or reviewing it is a significant exercise," Mr Nunn said.
"It could possibly be done as part of this work for this catchment, [and] applied to the whole LGA, or it could be done separately. That hasn't been determined.
"We were doing it anyway, but we will definitely be discussing that with [NEFRAG], and how that affects the American Creek catchment, Allans Creek catchment."
Mr Nunn claimed the review had been under way since last year - before the Mercury's investigation focused attention on it.
"It's time - it was last done in 2006," he said.
"We want to update the modelling and take into account changes."
The blockage policy dictates that flood risks are mapped, and any drain or culvert under the railway or freeway, if it is less than six metres wide, is assumed to be 100 per cent blocked in any major flood.
This has the effect of artificially turning the railway and freeway embankments into dam walls, increasing - on paper - the flood risk for residents.
Experienced engineers who have spoken to the Mercury say the policy is heavy handed and overly conservative, and should be replaced with a more site-specific evaluation of the risk of a drain becoming blocked.
Physical works recommended by NEFRAG would also be considered in the review.
The Allans Creek Floodplain Risk Management Committee will be re-formed by the council to oversee the review.
But the council will wait until it can get a $100,000 grant from the state government before starting the review after July.
Mr Nunn said this was so the council could employ a consultant to assist the committee.