And as the cost of repairs grows with the age of these structures, the imperative to act increase exponentially.
On the NSW North Coast, Kempsey Shire Council is well into a program of progressively replacing its 85 timber bridges. The latest and largest to be completed in the current four-year replacement cycle is the $4 million Turners Flat Bridge, jointly funded by the Shire and the Federal Government.
Turner's Flat is the last of the five downstream bridges over the Macleay River to be replaced - all in concrete.
The original timber structure, built in 1913, was washed away in flooding in 1949. A 130-metre, 11- span replacement timber bridge was commissioned in the early 1950's, but was closed for a lengthy period after two spans washed away in 2009.
Faced with an increasing maintenance burden, in 2017 Council applied for Commonwealth funding. Once this funding was secured and a tender process completed, civil contractor Waeger Constructions was chosen to design and construct the new bridge, with site work commencing in April 2019.
Officially opened to traffic in January, the new bridge is 144 metres long, with six 24-metre spans. It's constructed from pre-stressed concrete beams and concrete headstocks sitting on bored piles, with an insitu concrete deck.
Notwithstanding that the new concrete structure is slightly higher (1.8 metres) than the timber bridge it's replacing, Council still expects it to 'go under' a couple of times a year.