Volcanic disaster mitigation in the Philippines: experience from Mt. Pinatubo.

Considerable progress has been made in volcanic disaster mitigation in the Philippines during the last four decades, since the devastating Hibok-Hibok eruption in 1951 and the establishment of the Commission on Volcanology (COMVOL), the forerunner of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) in 1952. The management of the Pinatubo Volcano eruption crisis of 1991-92 marks the highest point in the development of volcanic disaster mitigation in the country. State-of-the-art volcano monitoring techniques and instruments were applied; the eruption was accurately predicted; hazards zonation maps were prepared and disseminated a month before the violent explosions; an alert and warning system was designed and implemented; and the disaster response machinery was mobilized on time. The unprecedented magnitude and lingering nature of the hazards, however, and their widespread, long-term impacts have sorely tested the capability of the country's volcanic disaster mitigation systems. In particular, the lahar threat has triggered controversies and put decision makers in a dilemma of choosing between adaptive versus confrontational/control approaches. At least three strategies have been articulated and adopted in varying degrees and forms: (1) the establishment of a lahar monitoring-warning-evacuation system to deal with the lahar problem on an emergency basis; (2) relocation of settlements from the hazard zones; and (3) installation of engineering countermeasures to control/divert the lahar flows and protect settlements. A combination of the three appears to be the best, but the most effective and least costly mix remains to be determined.