MONTREAL - With as much as 75 mm of water falling on Montreal in less than an hour, water gushed from the city's overwhelmed sewage system on Tuesday. Malls, schools, office towers and parts of the metro's orange line flooded as the Ville-Marie highway was closed.

On Wednesday, Mayor Gerald Tremblay defended his administration's $1 billion investment in the city's infrastructure over the past decade and blamed the "exceptional" rains for damage to the city.

"No system exists that could absorb such heavy rainfall," said Tremblay, flanked by his head of public works.

According to the mayor, the torrent was a once-in-a-century storm in certain parts of the city. He compared the deluge with a deadly flood in July 1987.

"We will put in place whatever measures are possible, but I won't say that it won't happen again," said Tremblay. "Depending on climate change, this flooding seems to occur with increasing frequency."

To help reduce the risk of flooding in the future, the mayor repeated that the city will spend a record $4.6 billion over the next decade nearly rebuilding the city's besieged water infrastructure. The construction of four new water retentions basins was recently announced.

With parts of Montreal's network dating from Victorian times, burst pipes and failing mains have been a staple for the past decade.

Damage to Montreal was largely reserved to the city's south-west borough, where hundreds of basements reported being flooded and tunnels under the Lachine canal filled with water.

Despite the investments, some Montrealers are complaining that they haven't seen the dividends of the spending.

"Two years ago this street was ripped up, re-sewered and re-piped, which took about seven months and was a nightmare and headache to deal with at the time and obviously that work was for nothing," said Tim O'Connor, standing in front of his St-Henri home.

With his basement full of water, O'Connor suffered a similar flood during a previous storm in 2008.

Within the first 24 hours, 30 claims were filed with the city, alleging that the city was at fault for damage to homes.

"We don't think we have a responsibility because of the nature of the exceptional floods that took place," said Tremblay, who invited homeowners to send in pictures and claims.

The Museum of Contemporary Art discovered on Wednesday that hundreds of pieces of art were damaged by the flooding, with two to three feet of water in the museum's basement. The MCA has yet to catalogue the extent of the damage or possible repairs.