Speaking at a planning dispute before the Victorian Civil and Administrative Tribunal earlier this month, Andrew Prout, a principal surface water engineer with more than 25 years' experience, described the area's flood rating as being in the "extreme hazard range".

He was called in as a witness by Melbourne Water in a hearing to decide if the owners of 21 Chifley Drive can demolish their existing house and build two new houses.

In a report tendered to the tribunal, Mr Prout stated: "If it were not for the long-standing residential use of the area, reinforced by the current zoning of the land, then in my opinion the flood hazard would make the area unsuitable for any residential dwellings."

He recommended:

* One replacement dwelling be the maximum allowed on a site in the flood plain.

* The council put a floodway overlay on the area instead of a land-subject-to-inundation overlay.

Mr Prout said residents might receive as little as three hours' notice of the flood peak arriving in Maribyrnong.

"Alternatively, if a flood event were to occur at a time when there are any delays in having skilled staff obtain and interpret real time data then the actual warning time could be less than three hours."

But flood warning expert Geoffrey Crapper, who developed the first rainfall-flood prediction model for the Maribyrnong River in 1975, argued that during past floods residents in Maribyrnong received about 10-12 hours warning to evacuate.

"Given that Melbourne Water's flood warning system on the Maribyrnong River has been operating successfully for 34 years it seems somewhat remiss not to make reference to the important part flood warning plays in minimising flood damage, personal trauma and the workload on emergency services..."

In the past 134 years the river has broken its banks 22 times, an average of once every six years.