Monitoring and statistical analysis of lanslides in Taiwan Island using multi satellite images and GIS Data

Earthquakes or torrential rains often lead to landslides. The Chichi earthquake in 1999 struck Nantou County of central Taiwan and caused civilian casualties of more than 2,400. The earthquake also turned the disaster areas into the sites of tens of thousands of landslides and rock avalanches. Added with the annual April–June Mei-Yu rain season and July–September typhoon season, Nantou County is further victimized by these elemental factors because it is one of the most affected areas during those seasons. With respect to the worsening scenario, this project attempts an in-depth look at the most damaged regions, using the high resolution SPOT satellite images taken in Septembers of 1999, 2002 and 2005. Landslide prediction is of spatial and temporal concerns, since these targeted sites cannot be thoroughly understood without knowledge of its geological past. This study thus examines the prospective changes in the entire measures of area of landslide sites in Nantou using Markov’s statistics model. The purpose is to develop a comprehensive methodology for conducting a random prediction of spatial and environmental factors in response to the transitory processes of the landslide areas. With the application of transition matrices derived from Markov’s model in the changes in future landslide coverage, it is estimated that the ratio of landslide will gradually stabilize from 1.02% in 2002 and 0.93% in 2005 to 0.82% in 2032. And from the analysis of Logit model, it is clear that the landslides are closely related to cumulated rainfall, altitude, slope gradients and geological formations, and in particular slope gradients having the greatest effect.