On 17th February 2006, a mudslide hit the village of Guinsagon in southern Leyte province in the Philippines. The slide covered 9km^2, was 3km wide and in places 30m thick. Half a mountain collapsed on the single village. .
The main cause of the mudslide was a La Ninya event in the Western Pacific. 200cm of rainfall fell in 10 days, weakening the slope strength. Slopes in the region are mostly very steep and mass movement and mudslides occur frequently.
Widespread deforestation during the past 70 years have also increased slope instability. The slide was ultimately triggered by a small local earthquake of magnitude 2.6Mw.
Exposure in that area of the Philippines is high. In 1991, 5,000 people were killed when typhoons triggered landslides, and a similar event in 2003 killed 133 people. Mudslides and landslides are a constant threat due to:
- heavy and prolonged rainfall from typhoons
- Steep hillsides largely built of weathered volcanic rock
- Extensive faulting and earthquake activity
Many villages are located at the base of steep slopes in the direct path of mudslides, and rural populations are high. The people are very poor and have high population growth. Southern Leyte is one of the poorest areas of the Philippines. Between 1995 and 2000 the population grew by +2.73%, placing pressure on environmental resources.
Logging bans have not been enforced by the government, largely due to political corruption. Even where sustainable logging has been practiced, in many places trees with shallow roots have replaced trees with deep roots, and thus made the slopes far less stable.
Survivors described how a “wall of mud” descended on the village, killing over 1,000 people, including 246 children at a primary school. Almost every one of the 300 homes was destroyed. The slide killed thousands of livestock and buried the farmland; around 16,000 people were affected.
Hazard mitigation maps have been made of Southern Leyte, but are not very detailed, so that villages that will be effected by mudslides cannot be identified. Following heavy rains and the deaths of 20 people in a nearby village, warnings were issued between the 4th and 17th of February, and several hillside villages were evacuated. However, many people chose not to leave.
Evacuation centres were set up around St Bernard, the capital of the region. Emergency aid in these centres provided safe drinking water, sanitation and health services. The region is very poor, however, so they cannot afford communications, which slowed down response times. Two hundred rescue workers were brought into the site. Unlike earthquakes, mass movements have few survivors.
International aid was provided by the Red Cross and Red Cresent, and their appeal raised US$1.6 million.
The government has commissioned a US$1.5 million geohazards survey and mapping of Leyte to try to prevent future similar disasters.