MGB: 22 Virac villages vulnerable to storm surges, coastal flooding

The Mines and Geosciences Bureau (MGB) of the Department of Environment and Natural Resources (DENR) has urged 22 coastal villages in Virac to implement recommended measures against the threat of storm surges and coastal flooding, including a 20-meter setback and no-build zone.

THE COMPLETION OF THIS PORTION of the expanded and lengthened boulevard along Virac población is expected to mitigate the effect of storm surges brought by powerful typhoons but the Mines and Geosciences Bureau urges the local government to implement a 20-meter coastal setback from the present high tide line within which no settlements will be allowed.

Last week, Mayor Samuel Laynes and key officials were briefed on the initial results of the Coastal Vulnerability Assessment conducted by a team from the MGB regional office in a field survey held July 2 to 6 in barangays Antipolo del Norte. Antipolo del Sur, Balite, Batag, Ibong Sapa, Igang, Magnesia del Norte, Magnesia del Sur, Marilima, Pajo Baguio, Talisoy, Capilihan, Concepcion, Francia, Palnab del Norte, Palnab del Sur, Rawis, Salvacion, San Juan, San Pablo, San Vicente and Sta. Cruz.

The team was composed of Supervising Geologist Mark Nino Miraballes, Senior Geologist Ryan Jay Mirana, and Geologist I Christian Coralde, assisted by personnel from the Municipal Planning and Development Office (MPDO) and the Municipal Agriculture Office (MAO).

The assessment involved field activities such as beach profiling, beach soil sampling, and documentation of the different physical factors that contribute to the vulnerability of coastal areas.

Observations were based on on-site slope measurements and characterization of sediments on the beach, with 22 samples submitted to the MGB laboratory for grain size analysis.

According to the team, the steepness or gradient of the coast reflects its potential for inundation and rapid shoreline retreat, with a gentle sloping coast susceptible to sea level rise inundating large extents of land.

Steep slopes and sea cliffs in the southwestern coast of Virac, especially in Balite, Batag, Marilima, Magnesia del Norte, Magnesia del Sur, Talisoy and portions of Igang, make them less vulnerable.

Steep slopes in the gravelly beaches of Pajo Baguio, Antipolo del Norte and Antipolo del Sur may also contribute to lesser vulnerabilities in these areas, the MGB team reported.

It said that storm surges during tropical cyclones affected the coastal barangays mostly during the “Amihan” or Northeast Monsoon season due to the slightly perpendicular orientation of their coasts to the monsoon winds.

Data from PAGASA regarding the dominant wind direction showed that easterlies will most likely affect the coasts, generating high energy waves that produce beach ridges and deposit gravel-size sediments along Antipolo area and from Capilihan to San Vicente.

Coastal erosion was also noted from Antipolo del Sur to Igang, with residents reporting about 15-meter-wide erosion and coastal retreat due to storm surges. since the 1980s.

The team, however, observed coral reefs along Balite. Batag, Marilima, the two Magnesias, Talisoy, Igang and portions of the población which serve as the first line of defense against high energy waves and thus need to be protected.

As to the presence of hard engineering defenses against storm surges, the initial survey showed what while several coastal barangays have such structures, these partially protect portions of the coasts and some of the structures have been damaged, making them less effective.

The team said the town proper is well protected by a 2.4 kilometer long sea wall, with ongoing reclamation activities observed in Capilihan, Ibong Sapa and San Vicente as well as in Palnab del Sur, where a pile of boulders was observed in the foreshore.

Overall, the initial geohazard assessment showed that almost all the surveyed barangays reported coastal erosion, storm surges and coastal floods.

The MGB team recommended the propagation and protection of coral reefs as they dissipate the energy of the waves impacting the coast.

It urged the local government units to establish or maintain the minimum 20-meter coastal setback from the present high-tide line pursuant to Presidential Decree 1067 and DENR Administrative Order No. 2021-07.

“Further settlement within the recommended setback should be prohibited,” it said.

It likewise recommended the enhancement of the level of awareness and preparedness of residents and communities exposed to coastal geohazards and the timely evacuation of residents living on the beach and hazard areas during severe weather conditions, with households and communities at risk to be relocated to safer grounds in the long term.

The team told the municipal government to implement a strategic land use plan that integrated the updated geohazard maps, with the design and construction of structures along the coasts to conform with structural and engineering codes.

Along Ibong Sapa, it called on the LGU to prohibit the extraction of beach material on areas within 200 meters landward and 500 meters seaward from the mean low tide level, as provided under the Philippine Mining Act and DENR Administrative Order 2010-21.

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