Tropical Storm Ketsana slammed ashore in the Philippines, killing dozens and stranding thousands on rooftops in Manilla’s worst flooding in more than forty years.

The estimated number of people displaced in the Philippines by a devastating storm on Saturday has doubled, to more than 435,000, according to government officials. The storm dumped a month’s worth of rain in six hours.

A massive rescue operation is underway, with the government relocating more than 100,000 people to 200 evacuation centers, and authorities working to distribute food, water, and medical supplies. But their efforts have been severely hampered by blocked roads and downed power and phone lines.

Meanwhile, residents are supplementing the government efforts by posting escape routes, meeting spots, emergency phone numbers, appeals for donations and the addresses of families in need of urgent assistance. Even celebrities are jumping in on the effort, including Demi Moore and Alyssa Milano who are urging her Twitter followers to donate.

Some even used Facebook to post locations of friends waiting for hours to be saved, mobilizing other users in their network who have easier access to government rescue to ask for help.

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