When was the greatest disaster in Manila?

On Sept. 27, 2009. Bagyong Ondoy brought floods in the whole Luzon area

here's a news clip from yahoo..

MANILA (AFP) - - At least 51 people were killed and more than 250,000 displaced after tropical storm Ketsana dumped the heaviest rainfall on the Philippine capital in more than four decades, officials said Sunday.

Desperate residents were stranded on rooftops after the nine-hour deluge on Saturday turned Manila's highways into raging rivers that swept away shanties and cars.

"This is the worst (flooding) that I have seen," Defence Secretary Gilberto Teodoro, who is heading the rescue efforts, said as he announced that 51 people had been confirmed killed with at least 21 still missing

The deluge left some areas of the sprawling city of 12 million people under up to six metres (20 feet) of water, forcing the government to declare a "state of calamity" that allowed authorities to use emergency funds.

More than 4,000 people have been rescued, either plucked by army helicopters from their homes or by rubber boats but many remained stranded on Sunday afternoon.

"If you are on the roof, don't try to leave. Just remain there and we will do everything to rescue you," Teodoro said in a radio broadcast.

In suburban Pasig city however, panicked residents were seen wading dangerously through neck-deep waters hoisting their children and belongings above their heads.

Amid the chaos, hospitals in the eastern part of the city were evacuated, while telephone and power lines were cut, officials said.

One of Manilas three airport terminals was also closed on Saturday, affecting several flights and stranding hundreds of passengers.

Teodoro said the storm had displaced nearly 280,000 people in Manila and five outlying provinces, with more than 41,000 victims seeking refuge in evacuation centres.

He said the floodwaters and the large numbers of stranded vehicles blocking roads were giving rescuers "a hard time" as they sought to reach those affected.

While the rains had temporarily ceased Sunday, Teodoro said more flooding may hit northern provinces if reservoirs burst their banks.

Philippine Red Cross chairwoman Gwendolyn Pang said rescuers were struggling to reach many areas, with many highways rendered impassable.

"This has never happened before. Almost 80 percent of metropolitan Manila is underwater," Pang told AFP.

In the district of Marikina, one of the worst-hit areas, rescuers waded in muddy floodwaters to reach the stranded, Red Cross official Dave Barnuevo said.

"The water is taking a long time to go down. The water is muddy and thick, and we have had to push our rubber boats in neck-deep flood (waters) in some areas," Barnuevo told AFP.

"We have rescued entire families marooned in their homes. They have not eaten and begged for food and water."

The government's chief weather forecaster Prisco Nilo blamed "climate change" for the severity of the storm.

He said that total rainfall for the nine-hour deluge was 41.6 centimetres (16 inches), breaking the previous single-day record of 33.4 centimetres in July 1967.