BAGUIO CITY, Philippines – Heavy rain over the past three days has pushed Metro Baguio past the landslide threshold, placing residents in the city and nearby towns of La Trinidad, Itogon, Sablan, Tuba, and Tubla at high risk of slope failures.
According to geoscientist Ricarido Saturay Jr, accumulated rainfall from September 20 to 22 has reached levels known to trigger landslides.
“Baguio rainfall in the past three days exceeded the threshold for landslide triggering: Chance of landslide occurrence is high,” Saturay, a Special Science Teacher at the Philippine Science High School – Cordillera Administrative Region, noted.
Saturay’s analysis is based on Philippine Atmospheric, Geophysical and Astronomical Services Administration’s (Pagasa) rainfall data and forecasts and a published rainfall landslide threshold curve.
Super Typhoon Nando battered northern Luzon on September 22, intensifying rainfall in Baguio, which was under Signal Number 1 when the typhoon made landfall at 3 pm over Panuitan Island in Calayan, Cagayan.
Data from Ogimet.com, which compiles official meteorological observations from the World Meteorological Organization’s Global Telecommunications System including Pagasa data, showed Baguio recorded:
When converted to average rainfall intensity, these figures exceed the intensity–duration threshold for landslides. Saturay stressed that Baguio has surpassed the minimum rainfall conditions likely to trigger slope failures.
He said Pagasa’s 5 am forecast on September 23 predicts at least 100 millimeters of additional rainfall in Benguet within the next 24 hours, increasing the risk.
A 2018 study by Dr. Dymphna Nolasco-Javier, former Dean of the College of Science at UP Baguio and now a lecturer, together with Kumar, served as the basis for the threshold curve used. The study was able to predict 93% of landslide-triggering rain events in Baguio from 2011 to 2013.
The study also noted that landslides typically occur after 24-hour rainfall equals 0.02% to 28% of mean annual precipitation, or after accumulating at least 500 millimeters from the onset of the rainy season.
Saturay said his analysis is based on a “practical and empirical approach that uses readily available rainfall data and research outputs.”
“This is a likelihood naman. Syempre hindi naman ito 100%. Pero statistically, mayroon at mayroong landslide [na] magaganap within [or close to] Baguio City,” he said.
On September 22, during a 24-hour rainfall period, a landslide struck Sitio Begis in Poblacion, along Marcos Highway in Tuba, Benguet, killing one person and injuring several others. The incident highlights the deadly risks that continue to threaten landslide-prone communities.
The University of the Philippines’ Nationwide Operational Assessment of Hazards (NOAH) lists Baguio City as having a high risk of flooding. This high hazard level indicates the city’s vulnerability to intense rainfall, overflowing rivers, and stormwater runoff, posing significant threats to residents, infrastructure, and local communities.
When there are continuous rains, residents are urged to stay alert, monitor local advisories, and prepare emergency plans. Avoid traveling to landslide-prone areas, secure your property, and ensure that family members know evacuation routes. Immediate action can save lives. - fyt.ph
(Editor’s note: The views expressed in this article are those of the featured geoscientist and do not necessarily reflect the views of the institution he is affiliated with.)
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