$137m Windsor Bridge flood ‘resilience’ cut to one-in-three year event

An expensive Hawkesbury River crossing had its ability to withstand flood wound back during the planning phase, it can be revealed.

The controversial $137 million Windsor Bridge was only built to withstand a one-in-three year flood, just 12 months more than the 140-year-old crossing it replaced.

Staying open for even a year — let alone three — has proven to be a challenge for the new link, which was a decade in the planning.

The bridge was cut last Wednesday and, as of 4.30pm today, was completely submerged.

Its current condition can be seen via a live traffic camera.

Windsor Bridge on Monday. Picture: John Grainger

The Windsor Bridge also flooded in March last year. Picture: Saeed Khan/AFP

It was also submerged in March last year.

Construction of the span began in 2018, a decade after it was announced. It opened in May 2020. The Telegraph can reveal the total bill was $137m — more than a third higher than was previously believed.

The original crossing, which had been in place since 1874, was removed.

In 2016, NSW Roads & Maritime Services published a Q&A on the replacement structure, which said: “The flood immunity of the new bridge will be around the one in three year flood level, whereas the existing bridge is about one in two years.”

In 2018, a NSW parliamentary committee was told that an early design had a higher flood resilience of one in five years, but that version was “amended in response to community feedback, and the height of the proposed bridge (was) lowered to a level that matched the flood resilience of key approach roads.”

RMS images of the bridge while it was in the proposal stage. Picture: RMS

Hawkesbury City Council’s Liberal mayor Patrick Conolly told The Daily Telegraph on Monday that the new bridge was “significantly higher” than the old structure.

“It wasn’t possible for it to be flood-free … without it being kilometres long,” Mr Conolly said, because the nearest high land was so far away.

A Transport for NSW spokesman said “the new Windsor Bridge was needed to replace the old bridge that had reached its end of life and increase the bridge capacity and width for communities and rural producers needing to get their goods to market.

“At 2.9 metres higher than the old bridge, the new Windsor Bridge is significantly more resilient to flooding and will be able to be open more quickly after flood events,” the spokesman said.