“Almost always, landslides will occur in areas where it has happened before.”
Landslide expert Dr. Beatriz Cuevas-Jadina stressed that for this reason, the Philippines needs continuous monitoring of its high-risk areas and a more comprehensive study on the causes and effects of landslides in the country.
An Associate Professor in Agronomy and Soil Science from the Visayas State University, Dr. Jadina has been studying high-risk landslide areas in Southern Leyte. She stipulated that the frequent occurrence of landslides in their province is associated with the presence of fault lines and heavy rainfall and not by human activities alone. Human activities like illegal logging are most commonly blamed for landslides since it usually happens in denuded mountainsides.
This conclusion is based on her study on GIS-Aided Bio-Physical Characterization and Assessment of a Landscape in Relation to Landslide Occurrences, which is supported by SEARCA’s Seed Fund for Research and Training (SFRT). She presented the highlights of her research during SEARCA’s Agriculture and Development Seminar Series (ADSS) on 12 April 2011.
Dr. Jadina’s research analyzed the causal and triggering factors contributing to the likelihood of a landslide. As an example, she described the events leading to the catastrophic landslide in St. Bernard, Southern Leyte in 2006, where a massive landslide killed more than a thousand people and destroyed homes and sources of livelihood. Before, and even on the day of the landslide, frequent earthquakes were recorded in the area where a major fault line is known to directly pass through. She also pointed out the loose soil in the steep mountainside, which was planted mainly with shrubs and coconut trees. She explains that seismicity (can be a causal or trigger factor), geologic formations, steep slopes, vegetation/land cover, and soil properties are the causal factors of a landslide.
Furthermore, she noted that a week before the landslide, unusually large amounts of rainfall was recorded in Southern Leyte, which most likely was one of the triggers of the incident. Other triggering factor include changes in groundwater level which was manifested with the presence of abundant springs emanating from the sides of “landslide cuts” in St. Bernard, said Dr. Jadina.
A few years after the disaster, people have again established their houses near the landslide areas, and started setting up farms and other livelihood options. This is contrary to what Dr. Jadina emphasized: that no home settlements should be within the four kilometer run- out distance of the unstable area; and that the mountainside should be planted with forest trees, rather than cash crops like coconut and agronomic crops. She also called for the continuous monitoring of rainfall by setting-up additional rain gauge stations as part of an early warning system for the people in the area.
Finally, Dr. Jadina challenged the students in the audience to help her in advancing the study of landslides in the Philippines. She sadly noted that very few studies on landslides exist and that the country is very far behind when it comes to understanding this deadly phenomenon. (Regine Joy P. Evangelista and Ann Valerie Gillado)
DISCLAIMER:
The point of view taken by this article is entirely that of the presenter's and does not reflect in any way, SEARCA’s position.
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