THE fatal landslide that struck Barangay Tina-an in the City of Naga last September 20 was the result of a natural phenomenon and man-made actions.
These were the findings of the ground penetrating radar (GPR) and georesistivity surveys (GRS) conducted by geologists sent by the Mines and Geosciences Bureau (MGB) Central Office to the affected site after the tragedy.
Seventy-eight persons lost their lives, while four remain missing after more than two hectares of Sitio Tagaytay collapsed and created a landslide that covered several houses in Sitio Sindulan.
Liza Manzano, MGB Central Office’s supervising geologist, said what happened on that fateful day was no ordinary “downslope of transport of soil and rock.”
The site, she said, has a rare geomorphology, or “the physical features of the surface of the earth and their relation to its geological structures.” The ground, which is mostly made up of limestone, has been degrading.
During Monday's dialogue that was attended by Department of Environment and Natural Resources (DENR) Secretary Roy Cimatu, landslide survivors and officials of the City of Naga, Manzano revealed the result of the GRS in the quarry site and its adjacent areas, which shows water underground, some with depths varying from five to 30 meters.
The image of the GPR also shows a cave with a height of six to 10 meters and static water with a depth of 12 meters under the landslide-stricken area.
Manzano said urbanization and industrialization caused the soil to degrade.
She also said water that was trapped underground tried to find an exit, which caused the ground level to drop.
“Kon gi-change mo ang (If you change the) natural (formation), any activity not only quarry, gi-change mo ang (you change the) natural land form. Magbag-o sad ang giagian sa mga tubig (You also change the course of the water),” she said.
The degradation of the soil in the area started right after the successive earthquakes of 2012 and 2013.
Manzano said the landslide site is near an active fault zone, which is why last Sunday’s magnitude 3.4 earthquake was felt there.
During the dialogue, Manzano showed Naga’s geohazard map. The MGB recognizes three zones in the city: the danger zone (yellow), no permanent habitation zone (red) and restricted zone (green).
Naga has many “red” areas, which means these areas are prone to landslide and should be off-limits to people.
Human settlement is allowed in the restricted zone, but only after a detailed landslide and subsidence hazard assessment is conducted.
But even though the MGB was able to shed light on what caused the landslide, it didn’t answer the question on most survivors’ minds: when can they return to their homes, or when will they move to a relocation site?
Renante Umambak, one of the evacuees, raised the matter. “Ang gipaabot sa mga tawo karon ang assurance kon kanus-a mahatag ang relocation ug unsay improvement (What we’re waiting for is the assurance that we will be relocated and if there’s any improvement),” he said.
City of Naga Mayor Kristine Vanessa Chiong said they’re waiting for the DENR to provide them with a list of areas safe for relocation, and of who can go back to their houses and who will need to be relocated.
She said the City Government is prepared to give survivors financial assistance.
“I will focus unsay mahimo kutob sa atong makaya (on what needs to be done). Lisod atong kahimtang pero mo-focus ta unsay atong mabuhat (We’re currently in a difficult situation, but we need to focus on what needs to be done),” she said.
However, she said the City can only afford to provide a relocation site to 500 households, based on the P13 million that they’ve received as donations after the disaster.
Chiong said the National Housing Authority earlier promised to build 356 houses for survivors on a portion of the Balili property in Barangay Tina-an that was donated by the Province.
But if the number exceeds 500 households, the mayor said they will seek additional financial assistance from the Capitol and First District Rep. Gerald Anthony Gullas. (SCG)