Severe inundation reminiscent of Tropical Storm Ondoy’s 2009 deluge crippled Metro Manila and surrounding provinces on Monday, August 17, trapping thousands of commuters in gridlock and prompting the suspension of government operations and afternoon classes.
The Metropolitan Manila Development Authority (MMDA) cited exceptionally intense rainfall driven by the southwest monsoon, locally termed habagat, as the catalyst for the widespread flooding.
According to measurements from the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) station at the Science Garden in Quezon City, the capital received 201.7 millimeters of rainfall over a five-hour span between 9 a.m. and 2 p.m. on Monday.
Because rainfall volume measures at 1 millimeter per liter of water per square meter, the recorded 201.7 millimeters equates to roughly 202 liters of water saturating every single square meter in just five hours, triggering rapid surface runoff.
For historic context, the catastrophic rains during Tropical Storm Ondoy on September 26, 2009, accumulated 455 millimeters over an entire 24-hour period.
“Mula 12 noon hanggang 2 PM (2 oras lang), umabot na agad sa 138 mm ang ibinuhos na ulan. Kaya naman mabilis na tumaas ang tubig at nagdulot ng baha sa iba’t ibang lansangan sa Metro Manila,” the MMDA stated.
In response to the emergency, the MMDA dispatched quick response units to assist stranded commuters and affected neighborhoods while actively tracking vulnerable areas through its urban CCTV network.
Concurrently, the Department of Public Works and Highways (DPWH) deployed heavy machinery and field personnel to clear drainage bottlenecks and accelerate the recession of floodwaters.