Undersecretary for Mining and Legal Affairs Deinrado Dimalibot said the municipal government of Jagna should immediately find a relocation site for the affected families.
"We asked our geologists and mining engineers who conducted the investigation in the area to return to Barangay Mayana because the landslides there are recurring," Dimalibot told The STAR.
"As it is now, the land appears unfit for (residential purpose). It should be enough reason for the immediate relocation of the people there," he said.
According to Dimalibot, the landslides in Barangay Mayana appear to be a "natural occurrence," saying that the instability of the underlying formation, called tuffaceous rocks, was possibly aggravated by the earthquake that occurred in the area four months ago.
In an initial assessment report, the DENR’s Mining and Geosciences Bureau (MGB) revealed that the presence of a fault as well as the periodic changes in the groundwater level in the area also affect the stability of the underlying rock formation.
The DENR-MGB said the periodic absence or lowering of the groundwater was caused by the shrinkage and compaction of the underlying clay materials during the dry months, while the increase in groundwater was due to the buoyant effect of rains on rocks.
A "very dry period" prevails in the area from March to May, while data from the adjacent Duero watershed revealed that rainfall from last June 1 to July 10 reached 5, 085 millimeters, the DENR-MGB said.
Dimalibot suspects that the landslide that occurred in Barangay Mayana last July 11 was caused by the geological conditions in the area, worsened by circumstances months before the landslide.
"The DENR will definitely be conducting an in-depth study of the geological composition of the area. But that would be for the long-term solution. In the short-term, there is an urgent need to evacuate the people to avoid further tragedy and casualty," Dimalibot said.
The DENR-MGB also recommended that the affected area and the villages along the path of the landslide debris should not be designated as "residential zones," and that there should be regular monitoring, preferably twice a day, of the progression of the landslide debris.
Dimalibot said the residents should be vigilant, especially during heavy rains, which could force the landslide debris to move faster.