Highway upgrades near Queensland-NSW border affecting floodplain and ecology, farmers say

Upgrades to the Newell Highway near Goondiwindi on the Queensland and New South Wales border are changing the way water flows across the floodplain and impacting farms and ecosystems, residents and experts say.

He says this is because the works at Newell Highway have raised the flood height and the speed of the flow east of the highway, while disrupting overland flooding to the west.

The upgrade between Mungle Back Creek to Boggabilla, jointly funded by the Australian and NSW governments, was officially opened on 13 April this year with the aim of improving the flood immunity of the highway corridor.

Mailler said that the rainfall event was not big enough to cause the magnitude of the flow that peaked on Saturday, indicating there was inadequate capacity in the causeways, culverts and bridges to clear the natural flooding due to the raising of the highway.

Prof Martin Thoms, a river science expert at the University of New England, said the highway upgrade between Goondiwindi and Whalan Creek would most likely have changed the hydrology of the floodplain.

Thoms said the impact would not only be felt by farmers, but also the natural floodplain vegetation and animals, including native Murray cod and catfish, which depend on the natural flooding of the floodplain.

He said there had not been sufficiently detailed hydraulic studies of the border rivers area to allay the worries of local landholders.

Thoms said even if the drains were designed to be in the same locations as before, the raising of the height of the highway would likely still have an impact.

Glen Smith, chairman of the organisation Border Rivers Food and Fibre, said the most recent flooding event was different to previous floods, in which equal amounts of water come from the Macintyre and Dumaresq rivers.

He said farmers sustain short-term crop losses after a flood event, but flooding underpins higher productivity in the long-term because it recharges the soil with moisture, sediments and nutrients.

Lawrence Springborg, the mayor of the Goondiwindi region, said the council conducts a review after any major flood.