The Mines and Geosciences Bureau (MGB) 7 has declared the 150-meter radius as “no habitation” zone after a rockfall incident which pinned down a couple to death recently in sitio Pangilatan in Barangay Cantao-an, Naga City, Cebu.
Dionisio Vilarmia, 42, and his wife, Julieta, 47 died when a boulder of 0.5-meter in diameter fell on their hut made of light materials. The couple’s two children aged 13 and 11 survived the accident.
As the area being confirmed as very critical, the MGB 7 also recommended the putting up of a warning signage informing the inherent danger or risk of the place, a possible diversion of a trail or road due to the proximity of the said site, and a close and regular monitoring on the progress of mass movement.
Senior Science Research Specialist (geologist) Abraham R. Lucero, Jr., who conducted the investigation yesterday said the vertical distance of the Vilarmia’s house is around 106 meters from the source of the rockfall.
“One of the effects of intense and prolonged precipitation is oversaturation of soil or rock debris that eventually decreases the shear strength of the rocks causing mass movement,” MGB 7 Regional Director Loreto B. Alburo said.
The findings, as well as the recommendations of the report were already discussed and relayed to Barangay Councilor Celso Aliganga who received the landslide threat advisory yesterday, for immediate implementation.
According to United Sates Geological Sciences (USGS), a fall begins with the detachment of soil or rock, or both, from a steep slope along a surface on which little or no shear displacement ha occurred. The material subsequently descends mainly by falling, bouncing, or rolling.
Alburo added our local officials should not be complacent and should take a serious look into the findings and recommendations on geohazards as lives and pieces of property are at stake here.
“We have the geohazards maps available at our websites in three government agencies and a non-government organization downloadable for free indicating the critical areas,” he said.
Data from the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) in Mactan showed that last September 4 from 1:40 pm to 2:47 pm, it recorded a rainfall of 23.7 millimeters and at 9:35 pm it went up to 40.6 millimeters.
Lucero explained that the rockfall is attributed to the heavy rains which dumped on that day, and the slope gradient of 70 to 80 degrees which is considered very steep.
The communities, Alburo added, should also pay attention to the warnings and should leave immediately the area if it is already declared as “no habitation” site by MGB 7.
To recall, three sitios in the said barangay were rated as very critical to landslide susceptibility and these were Pangpang, Tayad-tayad, and Balico.
The same findings in August 2011 also revealed that sitios Proper Cantao-an, Township, and Riverside were classified as high.