Philippines is compose of 7,461 islands and this islands has three main geographical section which are the Luzon, Visayas and Mindanao. And these section has different land-forms. These are the plains, valleys, hills, mountains and volcanoes. And some of these has a tendency to landslide.
What is a landslide? Landslide is a mass movements of rocks, debris and soil down a slope land. Landslides are just occurring naturally in our environment but eventually it has increase because of the human activities. Generally the factors can occur a landslide are slope angle, climate, weathering, water content, vegetation, overloading, geology and slope stability.
Natural Causes of Landslides
- Earthquakes – seismic activities has always been a reason of landslides around the globe. including in the Philippines. plate tectonic move the soil that covers them and moves together with it. When earthquakes occur on areas with steep slopes, many times the soil slips causing the landslides.
- Elevation of pore water pressure by saturation of slope material from either intense or prolonged rainfall and seepage
- Vibration caused by earthquake
- undercutting of cliffs and banks by waves or river erosion
- Volcanic eruption
Human Causes of Landslides
- Cutting of Trees – Clear cutting of all trees which completely removes all old growth timber from the area. this method is hazardous because it destroys the existing mechanical root structure.
- Removal of vegetation.
- Interference with, or changes to natural drainage
- Leaking pipes such as water and sewer reticulation
- Modification of slopes by construction of roads, railways, buildings, etc
- Mining and quarrying activities
- Overloading slopes
- Vibrations from heavy traffic, blasting, etc
- Excavation or displacement of rocks
SO HERE’S THE TOP 10 LANDSLIDE PRONE AREAS IN THE PHILIPPINES
- Benguet (90.3%)
- Mt. Province (87.1%)
- Nueva Vizcaya (86.7%)
- Kalinga Apayao (84.7%)
- Southern Leyte (82. 7 %)
- Abra (82.1%)
- Marinduque (78.6%)
- Cebu (77.8%)
- Catanduanes (77.4%)
- Ifugao (77.3%)
Futhermore, these are the provinces that are prone to flash floods and landslides. Basilan and Lanao del Sur in the Autonomous Region in Muslim Mindanao; Abra, Apayao, Benguet, Ifugao, Kalinga and Mountain Province in the Cordillera Administrative Region; Negros Occidental in Negros Island Region; Ilocos Norte, Ilocos Sur, La Union and Pangasinan in Ilocos region; Batanes, Cagayan, and Nueva Vizcaya in Cagayan Valley; Aurora, Nueva Ecija, Pampanga, Tarlac, and Zambales in Central Luzon; Occidental Mindoro and Oriental Mindoro in Mimaropa region; Zamboanga del Sur in Zamboanga Peninsula; Albay and Sorsogon in Bicol; Aklan, Antique, Capiz and Iloilo in Western Visayas; Misamis Occidental in Northern Mindanao; and Compostela Valley and Davao Oriental in the Davao region.
So why in these Provinces?
Basically, landslides is present in places when there are mountains and high elevated places surrounding an area. As seen on the list given by the DENR-MGB, all of the provinces in the Cordillera Administrative Region or CAR are included in the top ten landslide prone areas in the Philippines. This is because the entire region is located “on and around the Cordillera Mountain ranges” and so after period of heavy rains or when typhoon or earthquakes occur, the land on the hills and mountains becomes soft and unstable which makes the region susceptible to landslides. This also holds true to other provinces listed like Southern Leyte which is characterized as “relatively flat lands” where the people reside but “rugged and mountainous towards the interior”, Cebu and Catanduanes, the topography of which is described as “rugged and mountainous.” Landslides are believed to be caused by, among others, heavy rains, earthquakes, volcanic eruptions and by man-made causes like mining and commercial developments.