VicRoads yesterday announced the central alignment as its preferred path for the $56.9 million works to upgrade the flood-prone highway between Sale and Longford.

The upgrade, known as the Stage Three Cox's Bridge Project, involves raising the highway 1.5 metres above the existing highway for 2.8km from the edge of the Swing Bridge realignment to the southern edge of Sale.

VicRoads considered two options for the realignment, the central and the western, which would have involved the closure of the Thomson River Caravan Park.

VicRoads regional services executive director Steve Brown said the central alignment option would better protect the road from flooding by raising the road height by an average of over one metre.

He said the route was chosen after extensive community consultation and submissions on the proposed Planning Scheme Amendments.

''The entire stretch of South Gippsland Highway between Sale and Longford will be protected up to a one-in-twenty year flood event,'' Mr Brown said.

''The highway upgrade will not only better protect the South Gippsland Highway from flooding and the associated lengthy detours, it will also improve safety by lowering the number of sharp bends in the alignment.''

Mr Brown said the alignment would involve the removal of the row of elm trees near the Thomson River Caravan Park, rather than the park itself.

He said cuttings would be propagated and planted close to the area.

According to Mr Brown, the caravan park would not be affected by the road upgrade, and there would be minimal impact on the Sale Common Game Refuge which forms part of the Gippsland Lakes Ramsar-listed wetlands.

''There will also be other vegetation offsets in the Sale Common and surrounding areas in accordance with Victoria's Native Vegetation Management policy,'' he said.