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What are the landslide triggering factors?

The landslide triggering factors include internal, external and human factors.

The internal factors of landslide formation are related to the soil and rock materials, including (1) soft and weak rock properties or rock strata with multiple joints or shear fracture zone; (2) geological structure; (3) topography; (4) vegetation. All of these can reduce the binding or frictional force of rock particles.

The primary external factors that can trigger a landslide include: (1) weathering of rock strata; (2) increased pore water pressure, such as the infiltration of rainwater or rise of groundwater surface; (3) increased loading by, for example, rainfall, accumulated snow or flourish vegetation; (4) the supporting forces of toe have been removed by, for example, weathering, erosion, early landslide or faulting; (5) collapse of underlying strata; (6) an increase in lateral pressure, such as rock fissure, freezing water; expansion of clay materials and so on; (7) earthquakes and vibrations; (8) torrential rains; (9) other factors, such as site subsidence resulted from limestone cave.

Some of external landslide triggering factors are counted as human factors. For example, remove a portion of slope toe (the slope can become steeper); build houses on the slope (the building can increase the slope loading); and pile up man-made wastes (increase the driving force of materials on the slope). Besides, an inappropriately selected site can also affect the slope stability and trigger a landslide. For example, construct a road on top of or below the slope; or prepare the site to have a flat land.

For more information, please go to the “Taiwan Geoscience Portal” website.