Did the wall that saved the Melbourne Cup racetrack contribute to the flooding of 245 homes?

As the people whose houses were swallowed by the Maribyrnong River dragged their ruined belongings into the street this week, until the piles of junk towered overhead, marquees were being erected downstream at Flemington racecourse.

Engineer Geoff Crapper met the Trewins during the battle against the wall, back in the early 2000s.

At the time, he had been a Melbourne Water employee for more than three decades, and was one of several experts who questioned the flood modelling relied upon by the authority to approve the wall.

He made five recommendations, including that the modelling be independently reviewed. Ultimately it was, but Melbourne Water still approved the wall.

He says this is what makes the investigation into the flood so critical: it will be the only way to determine what happened.

Investigators, he says, should be going into every house that flooded to determine the level the water reached, starting from Chifley Drive in the north, then moving downstream to measure levels at the wall itself, through the Kensington Banks estate, parts of which were also flooded, and at other markers as far down as Footscray Road.

Crapper reckons it is not just the flood wall that must be examined.