The 17 February 2006 rock slide-debris avalanche at Guinsaugon Philippines: a synthesis

Abstract

The paper presents a synthesis of the key findings of the conference and workshop convened to consider the causes of and lessons to be learned from the disastrous rockslide-debris avalanche on 17 February 2006 in southern Leyte, Philippines. Some 1,221 people died and the barangay of Guinsagon was buried. The geology, historical seismicity, progressive disintegration of the rock mass, development of smectite layers and the continuous development and movement of shears within the Philippine Fault Zone combine in the steep rugged terrain to produce massive landslides, of which the 15 million m3 Guinsaugon event was the latest. The relevance of recent heavy rain and an almost synchronous seismic event are considered but it is concluded that the movement was the result of progressive failures and tectonic weakening while the landslide hazard was increased by the presence of rice paddy fields in the valley bottom. An anecdotal time to failure curve is presented, based on eyewitness accounts and observations of instability. Attention is drawn to the importance of both the education and training of the local people in the recognition of signs of potential movement and a reporting management system. Such simple measures could save lives and empower local communities to take some ownership of their level of landslide risk.