ILOILO CITY: The Mines and Sciences Bureau (MGB) regional office here has found a significant number of sinkholes and caves in at least 17 villages in the municipality of Buenavista, Guimaras Island.
This was reported after the MGB completed the karst subsidence hazard assessment of the town earlier discovered to be rich in limestone.
Regional Director Leo Van Juguan said the municipality has 88 sinkholes and 85 caves with some sinkholes measuring from one meter to more than 50 meters deep and covering as wide as one kilometer.
The assessment inventory was conducted from September 2 to October 7, 2015 in 17 barangays of Buenavista town – Agsanayan, Dagsa-an, Daragan, Getulio, Mabini, Montpiller, Navalas, New Poblacion, Salvacion, San Isidro, San Miguel, San Pedro, San Roque, Tacay, Taminla, Tastasan and Zaldivar.
In the Philippines, subsidence hazard in karst terrain have not been given much attention in the past until the strong earthquakes in Negros Oriental in 2012 and in Bohol in 2014 which exposed numerous sinkholes in these areas.
These phenomena were proven destructive and have affected build-up communities, roads, schools, administrative buildings and agricultural farmlands.
The karst terrain is characterized by barren, rocky ground, caves, sinkholes or underground rivers, with the absence of surface streams and lakes. It results from excavating effects of underground water on massive soluble limestone.
Juguan said the recognition of the devastating damage that can result from this hazard and the presence of extensive karst areas in the country prompted the MGB to include karst subsidence assessment in the National Geohazards Mapping and Assessment Program.
Meanwhile, vulnerability risk assessment targets to be completed in 2016 are in towns of Leganes, Zarraga, Pavia, Barotac Nuevo and Oton in the province of Iloilo; Laua-an, Barbaza, Patnongon and San Jose in Antique; Numancia in Aklan; as well as in the town of Sigma in Capiz, and San Enrique, Negros Occidental.
The risk assessment was also conducted in Kalibo, Aklan and Bago City, Negros Occidental in 2015.