About 600 properties in Melbourne's inner west were inundated when the Maribyrnong River broke its banks on October 14, 2022.
But the Melbourne Cup track remained clear because of a 2.5m wall built in 2007.
Former Federal Court judge Tony Pagone was tasked with investigating the impact of the wall as part of an independent review established by Melbourne Water into the Maribyrnong floods.
His final report, released on Friday, found the wall contributed to extent of flooding across the catchment by roughly one per cent.
Flooding depth was increased from between 0.8 to 3cm for about 240 properties in the Maribyrnong township.
"(The construction of 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.
Despite this finding, Melbourne Water said it did not believe there was enough evidence to justify removing the wall.
"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.
She said Melbourne Water would incorporate the flood wall examination into its broader investigation of mitigation options across the catchment.
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