Flood-ruined WA bridge to be rebuilt six times stronger

A bigger, stronger bridge will be built over the Fitzroy River after once-in-a-century-flooding in Western Australia's Kimberley washed away its predecessor, cutting a key transport route.

WA Minister for Planning Rita Saffioti says the new bridge on the Great Northern Highway at Fitzroy Crossing would be 100m longer and twice as wide as the old one, with piers about double the depth.

"We've all seen the pictures of what happened to that bridge, it means there is a complete disconnection in the north of our state," she told reporters on Wednesday, referring to the January flood that swept away homes, businesses and large sections of the only road to the north of the state.

Ms Saffioti said the new bridge would be 270m long, four traffic lanes wide, with pylons that reach about 40m into the river bed.

"What was identified was significant sand movement (during the flooding) and as a result the piers will need to be sunk deeper," she said.

The minister said the new structure would be six times stronger than the old bridge and be able to handle a one-in-2000-year weather event.

"It's being prepared to withstand far greater events than occurred in the past three months," she said.

The WA government has signed a contract to build the new bridge with a consortium of three companies once the design and planning are finalised.

Work is also under way to relocate telecommunication cables and water and sewage pipes built into the old structure.

It's hoped some vehicles would be able to travel over the new bridge by mid-next year.

In the meantime, road freight to and from the north of the state must travel via a much longer and costly route using the Stuart Highway in the Northern Territory and South Australia.

Smaller vehicles are crossing the Fitzroy River using a barge, but it is understood to be booked out until after Easter.

The WA government is also working to open two low level river crossings, with the first for small vehicles almost complete and set to open in April if the water level continues to drop.

A second two-lane crossing is also under construction 150m upstream of the old bridge to cater for higher traffic volumes, including road train and pedestrians.

Main Roads WA hopes to open this by May for access across the river during this year's dry season, when tourists flock to the region.