The proposed Rivers Run Estate would be the largest development in the town for well over a decade, but its position on the edge of the Moyne River floodplain has created potential conflicts with the shire's planning scheme.

The planning scheme is in the process of being amended (amendment C69) to revise the areas in and around Port Fairy that are appropriate for development. A separate amendment to grant planning permission for the Rivers Run Estate (amendment C75) is going through council at the same time.

A crucial element of the C69 amendment, which implements the Port Fairy Coastal and Structure Plan, is agreement over the flood-prone areas of the town and how high flood waters would rise in 2100 under a one-in-100-year flood.

Responding to community feedback on C69, the council commissioned new flood modelling to replace the previous study, which was completed in 2010.

The new study shows flood waters in 2100 under a one-in-100-year event would reach a maximum of 3.3 metres above normal sea levels.

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The C75 planning amendment uses different flood modelling produced by Water Technology, the company that produced the 2010 study. The Water Technology modelling shows maximum flood levels in the same scenario topping out at 2.79 metres above sea level, more than half a metre less than the new council study.

The development proposal for Rivers Run uses the 2.79 metre figure for the entire estate, meaning that according to the new council document the estate would be half a metre under water in a worst case scenario flood.

Some areas of the Rivers Run site are under even the lower 2.79 metre threshold, with the developer proposing a "cut and fill" process that would move thousands of cubic metres of earth to build up the lower lying areas.

But if the proposal had to comply with the 3.3 metre threshold, this would require a radically larger cut and fill process.

The Port Fairy Local Floodplain Development Plan, which sets the rules for building in areas affected by the flood overlay, states that any planning permit must "strongly discourage filling of the floodplain in all areas within the... FO (flood overlay) unless it can be demonstrated that balanced cut and fill can be achieved consistent with the Glenelg Hopkins CMA Guidelines for Floodplain Cut and Fill".

The council's new flood modelling will also alter the flood overlays for Port Fairy that dictate restrictions on development. Under the current flood overlay only the bottom corner of the Rivers Run site is affected, but under the new modelling the majority of the estate would be within the overlay.

Both the C69 and C75 amendments are still in the early phases of the approval process and Moyne Shire Council's director of economic development and planning, Brett Davis, said the conflicting modelling would be resolved in due course.

He said the fact the two amendments were being considered simultaneously wouldn't create any headaches.

"Council is progressing the two amendments to enable any discrepancy between the new modelling in C69 and the previously-prepared development plan as part of C75 to be cohesively resolved," he said.

Mr Davis said the developer, Michael Hearn, had been advised over "a number of discussions" of the differences in the two studies.

The Standard approached Mr Hearn as well as his planning consultant for comment, but they did not respond.

Mr Davis emphasised both amendments would have to go to the Glenelg Hopkins Catchment Management Authority for assessment.

The amendments are currently out for public feedback, after which Moyne Shire councillors will propose any changes they think necessary. It is likely the amendments will then go to Planning Panels Victoria and ultimately to the Minister for Planning.

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