MGB: Coastal erosion caused Zambales beach collapse

MANILA, Philippines - The Mines and Geosciences Bureau (MGB) yesterday said that the collapse of the coastline of a beach resort in Candelaria, Zambales does not constitute a “sinkhole” phenomenon but was a result of coastal erosion.

MGB Director Leo Jasareno said they are recommending that the area be declared permanently as a “no swimming” and “danger” zone as well.

Jasareno said with the use of “ground penetrating radar” (GPR) equipment, a team of geologists who conducted an investigation found no voids or cavities, or even a sinkhole in the affected area.

“What was identified were alternating layers of loose and fine to coarse sand 18.5 meters below the surface,” he said.

The equipment functions like an X-ray that can check land sinking up to 100 meters or 300 feet below.

“The beach slump is not due to sinkhole but is a result of coastal erosion caused by wave and tidal currents. Waves undercut the base of the shoreface, which happened during the interface of low tide and high tide, with the prevailing southwest monsoon,” the MGB report said.

Jasareno noted that the area is underlain by unconsolidated beach sand that is unstable and easily reworked by waves.

“The coastal sedimentation dynamics is indicated by the advance and retreat of the shoreline, and that the area is also prone to storm surge hazard,” he said.

He said coastal erosion is a natural phenomenon leading to the formation of a cliff 100 meters from the shoreline. The depth of the cliff or the steep slope from the shoreline is about 25 to 30 meters.

The MGB recommended continuous monitoring of the area for large-scale erosion and storm surge, particularly when there is an incoming weather disturbance.

“A danger zone should be declared as the area is highly prone to coastal erosion,” he added. The MGB estimated the danger zone to be 100 kilometers long and the width to be 20 to 30 meters.