About 600 properties in Melbourne's inner west were flooded when the Maribyrnong River broke its banks on October 14, 2022.
But the Melbourne Cup track remained clear because of a 2.5m high and 900m long wall built in 2007.
Former Federal Court judge Tony Pagone investigated the impact of the wall as part of an independent review established by Melbourne Water into the Maribyrnong floods.
The flood wall at Flemington Racecourse has been criticised in a report following flooding in 2022. (James Ross/AAP PHOTOS)
His final report, released on Friday, found the wall contributed to the extent of flooding across the catchment by about one per cent.
Flooding depth was increased between 8 to 10mm in the upstream areas and up to 30mm in downstream parts of the Maribyrnong township, impacting about 240 residential properties.
"(The flood wall) most likely resulted in flooding of some houses that would otherwise not have flooded and increased the flood damage in houses that would have been flooded in the absence of the flood wall," the report stated.
"The information provided to the review panel also clearly indicates that the compensatory works were largely ineffective at mitigating the effect the flood wall had on the October 2022 flood event."
Modelling showed flooding of the industrial areas of West Melbourne and Kensington next to the river was 60 to 65mm higher because of the wall.
Compensatory works reduced the flood level between 8mm to 10mm about 500m upstream of Footscray bridge and between 4mm to 8mm for a further 2km upstream.
The scale of flooding sparked an independent review into the Maribyrnong event. (Erik Anderson/AAP PHOTOS)
"Beyond this, the impacts of the compensatory works were negligible," the report said.
Despite the wall's impact on homes, Melbourne Water said it did not believe there was enough evidence to justify removing it.
"The independent review panel does find the mitigation works put in place to offset the impact of the wall didn't perform as well as expected," managing director Nerina Di Lorenzo said.
"We will now incorporate an examination of the flood wall mitigation into our broader investigation of potential mitigation options across the catchment."
The Victoria Racing Club, manager of the renowned racecourse, said the flood wall was approved by the Bracks government in 2004 and complied with all relevant requirements.
The club had received the final report on Friday morning and will consider its findings, including those relevant to the racecourse.
"We remain committed to working with the appropriate authorities on this matter," VRC said in a statement.
The review also concluded the levee had no measurable impact on the Rivervue Retirement Village in Avondale Heights, where 70 residents were forced out of their homes following the inundation of 47 properties.Â
A state parliamentary inquiry into the 2022 statewide floods heard Melbourne Water's modelling completely underestimated the risk to Rivervue.
The agency said it would continue to implement 15 recommendations made by Justice Pagone in 2023.
The Victorian government has been contacted by AAP for comment.
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