Natural forces cause landslide in Hamtic

A massive landslide that occurred in Hamtic, Antique was caused by natural forces, a Mines and Geosciences Bureau (MGB) report disclosed.

The MGB cited the Lagdo formation or the underlying rocks in the area (characterized by Andesitic lavas, mudstones with fragments of volcanic rocks, limestone, etc.), steep slope, and high elevation (197 to 215 meters above mean sea level) as the primary trigger factors which caused the massive landslide that has affected Brgy. Pamandayan and Brgy. Bongbongan 3 in the municipality of Hamtic, Antique.

“Moreover, the heavy rainfalls brought about by monsoon rains due to three strong typhoons, namely: Quinta (October 24-27, 2020; Rolly (October 26-November 6, 2020); and Ulysses (November 8-15, 2020) caused the over-saturation of soil which also triggered the landslides,” the MGB assessment report read.

The landslide, which occurred on November 17, 2020, affected an approximate land area of 16.629 hectares, with at least four houses totally or partially damaged. Fortunately, no casualty was reported due to the landslide.

During the assessment, the composite team from MGB and Provincial Environment and Natural Resources Office (PENRO) in Antique noted the damming or choking of the Matha River which traverses the northwestern flank of the landslide area. The vegetative cover of the area includes tall trees, shrubs, and grasses.

Under the National Geohazard Assessment and Mapping Program (NGAMP) implemented by the Mines and Geosciences Bureau of the Department of Environment and National Resources (MGB–DENR), the inspected areas in Hamtic were classified as having moderate to very high landslide susceptibility rating. After the assessment and field observations, however, they were reclassified as having very high landslide and flood susceptibility rating.

The mass movement type or the landslide incident was classified as debris avalanche. The landslide also caused the damming of the Matha River while several tension cracks were noted adjacent to the slope where the landslide occurred, the MGB report said.

With the impact of the landslide, the MGB has warned dwellings should no longer be allowed in those areas and are neither suitable for commercial, industrial and institutional developments. The establishment of evacuation centers is discouraged as well while warning signages should be installed in the area.

MGB recommended that residents downstream of the landslide area must remain vigilant, especially those residing near Matha River, during severe weather conditions.

The Municipal Disaster Risk Reduction and Management Office (MDRRMO) of Hamtic, Antique has advised the residents near Matha River to relocate on safer grounds.

PENR Officer Andres T. Untal was in the middle of a webinar but asked permission to leave to join the team in the conduct of the area inspection. MGB’s Geologist II Shimpei A. Francisco and Science Research Specialist II Eliaflor B. Bulawin inspected the landslide areas in Brgys. Pamandayan and Bongbongan 3 in Hamtic, Antique.

DENR Secretary Roy A. Cimatu kept encouraging local government units to revisit the geo-hazard maps distributed to them by the MGB as their guide for disaster preparedness and management. (DENR-6)