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GEO: How to Differentiate Between Landslide and Slope Failure

Diagram of landslideIn light of global climate change, Taiwan has faced challenges ranging from earthquake to typhoons to torrential rain in recent years. Given Taiwan’s unique soil quality and its position on top of the Ring of Fire, many of these natural disasters often set off landslides and slope failures.
 
Roughly 15,000 hectares of slope land lies within the parameters of Taipei City, accounting for roughly 55% of the city’s total area. During rain season between May and November each year, storms and typhoons dump a significant amount of water over the city, which increase the possibilities of landslide and slope failure.
 
So how can one tell the difference between a landslide and a slope failure? To the untrained eyes, the shocking sight of mud and rocks flooding down the side of a mountain slope may look the same.
 
According to the Soil Conservation Service (SCS) of the Executive Yuan’s Council of Agriculture, the definition of landslide is a natural phenomenon involving masses of mud, sand, gravel, and boulders mixed with water flowing down from high elevation areas via slope surface due to gravitational pull.
 
On the other hand, slope failure refers to the movement of shallow layer soil and stones along unstable slope surfaces. This is the more common type of disaster witnessed by the public.
 
Chief Chu of the Geotechnical Engineering Office’s (GEO) Mud/Rockslide Control Section pointed out that the agency commissioned professional teams to conduct research at risk areas, as well as patrols and monitoring. In addition to the 26 rain measurement stations and 11 observation stations keeping track of rivers with landslide-inducing potentials, combined with the 19 rain measurement stations established by the Central Weather Bureau, this network plays a key role in tracking both rainfall and changes to soil during storms.
 
For related information on soil conservation, the agency suggests the following Chinese websites:
SCS Landslide Prevention Information Website  [Link]:
Taipei City Mountain Slope Information Website: [Link]
Taipei City Disaster Prevention Information Website: [Link]