The bridge, which is the only river crossing between Nagambie and Murchison, has been closed since the flood, as council waited for the assessment.
Mayor Laura Binks said the bridge would either need to be replaced or have extensive structural repair and strengthening works done.
The report said “extensive rot” and surface corrosion had damaged the bridge over a long period of time, with the floods not the only factor in the bridge’s condition.
Cr Binks said once council was able to put a cost on either option, it would begin community consultation to decide which path to take and “to ensure the bridge remains open and is safe for the next 50-plus years”.
“We will then need to advocate strongly for Victorian and federal government funding to complete the works, and we ask for the community’s support, which will help strengthen our efforts, meaning greater chance of success.”
Cr Binks said extensive repair work needed to be done before the bridge could reopen.
“We understand the impact of this news to the Kirwans Bridge community. We know how important access across the bridge is to residents and visitors,” she said.
“We want to reassure our community our goal is for a sustainable, long-term future for Kirwans Bridge.”
The Kirwans’ Bridge Action Committee released a statement earlier this week, before council’s announcement, calling for the bridge to be reopened.
The group said 3700 vehicles used the “vital piece of infrastructure” used by communities in Nagambie, Rushworth, Murchison and beyond.
The group said ambulances had been delayed by the bridge closure, and fire evacuation options had been reduced by the bridge’s closure, while school bus services had also been cut due to the quality of the road.
In addition, some patients in the area using in-home care services had been faced with a 300 per cent hike in travel charges, according to the group, while business costs had increased.