VSU study explains why landslides occur

BAYBAY CITY, Leyte ,Philippines  – “Almost always, landslides will occur in areas where they happened before.”

Thus warned Dr. Beatriz Cuevas-Jadina of the Visayas State University (VSU) here as she stressed the need for the country to continually monitor high-risk areas.

She also recommended the conduct of more comprehensive studies on the causes and effects of landslides.

Dr. Jadina, an associate professor in Agronomy and Soil Science at VSU in this seaside city situated 120 kilometers south of Leyte’s capital city of Tacloban, has been studying high-risk landslide areas such as in adjacent Southern Leyte.         

She noted that the frequent occurrence of landslides in the province is associated with the presence of fault lines and heavy rainfall and not by human activities alone.

Human activities, such as illegal logging, are most commonly blamed for landslides since they usually happen in denuded mountainsides.

Dr. Jadina based her conclusions on her study titled “GIS-aided Bio-Physical characteristics and Assessment of a Landscape in Relation to Landslide Occurrences”.

GIS stands for geographical information system.

The study was supported by the Los Banos-based, Philippine government-hosted Southeast Asian Ministers of Education Organization-Regional Center for Graduate Study and Research in Agriculture (SEAMEO SEARCA).

SEARCA, headed by Director Gil C. Saguiguit Jr., is one of the 20 “centers of excellence” of SEAMEO, an intergovernment treaty body founded in 1965 to foster cooperation among Southeast Asian nations in the fields of education, science, and culture.

Supported by SEARCA through its Seed Fund for Research and Training (SFRT), Dr. Jadina’s research analyzed the causal and triggering factors contributing to the likelihood of a landslide, as reported by Regine Joy Evangelista and Ann Valerie Gillado.

The VSU professor discussed the results of her study at the recent weekly SEARCA Agriculture and Development Seminar Series.

As an example, Dr. Jadina cited the events leading to the catastrophic landslide in St. Bernard, Southern Leyte, in 2006 where more than a thousand people were killed and many homes buried.

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, Dr. Jadina said.

She also pointed out the loose soil in the steep mountainside, which was planted mainly to coconut trees and shrubs. She explained that seismicity (which can be a causal or trigger factor), geologic formations, steep slopes, vegetation/land cover, and soil properties are causal factors of a landslide.

Furthermore, she observed that a week before the landslide an unusual large amounts of rainfall were recorded in Southern Leyte, which most likely was one that triggers of incident.

Other triggering factors included changes in groundwater level which was manifested by the presence of abundant springs emanating from the sides of “landslide, cuts” in St. Bernard, Dr. Jadina added.

A few years after the disaster, people again built 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 set up within the four-kilometer run-out distance of the unstable area; and that the mountainside should be planted to forest trees, rather than cash crops such as coconut and agronomic plants.

She also called for the continued 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 enjoined the students in the audience to help her in advancing the study of landslides in the Philippines.

She noted that very few studies on landslides exist and that the country is very far behind when it comes to understanding this deadly phenomenon.