Tropical Storm Ketsana, locally referred to as Ondoy, deluged Manila and surrounding areas with 455mm (18 inches) of rain in 24 hours Saturday, killing 240 people and displacing 609,548 according to SitRep 12 (29 September) from the Philippines National Disaster Coordinating Council (NDCC). Ketsana caused the country’s worst flooding in 42 years, according to the Philippine government and observers on the ground.
The numbers of dead and displaced are expected to rise significantly as floodwaters recede, allowing rescuers to gain access to isolated areas, and health officials have expressed concern about the spread of swine flu, diarrhea, and leptospirosis.
Rainfall from Tropical Storm Ketsana as estimated by NASA’s TRMM satellite, several hours before the heaviest rainfall began in Manila. The small core of rainfall rates off-scale (greater than 1.6 inches/hour) to the east of Manila, and passed directly over the city between 8am and 2pm local time on 25 September. Source: Navy Research Lab, Monterey, California. Click to enlarge.
410.6 mm (16.2 inches) of rain fell in Quézon City in the nine hours immediately after Ketsana made landfall, surpassing the previous 344.5mm record for rainfall in the Philippines in a 24-hour period, recorded 7 June 1967. Images and video distributed through social networking resources such as Facebook, Twitter, and YouTube (sample YouTube video) showed vehicles floating down city streets, 80% of which were flooded in Manila at the height of the storm.
Nathaniel Cruz, weather services bureau head of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), told GMANews.TV that “This could be again a manifestation of climate change. Due to climate change, we should expect more extreme weather events like extreme rainfall."
Early official blame was placed in part on citizen inaction and refuse-choked drainage systems. In an interview with the Philippine Daily Inquirer, Dr. Prisco Nilo, chief of PAGASA, said that flood warnings had been issued prior to the storm, and that “instead of just watching the soap operas on TV, [people] should also watch the news.”
As the severity of the event became apparent, however, the Marikina River crested its banks, and officials worried that additional rains could weaken dams. Portions of the Malacañang presidential palace in Manila were converted into refugee shelters. Although President Gloria Arroyo has termed Ketsana a “once in a lifetime event”, flooding in Manila has steadily become more frequent and more severe in the latter half of the century, in part due to heavy groundwater extraction, which is causing the land around Manila Bay to sink.
Ketsana has since strengthened into a typhoon, and is expected to intensify further as it approaches Vietnam, Laos, and Thailand, according to a government weather forecaster. A second tropical depression is now forming in the Pacific Ocean, and is heading toward the Philippines.
—Jack Rosebro
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