The Impact of Typhoon Morakot in 2009 on Landslides, Debris Flows and Population in the Chishan River Catchment, Taiwan

Abstract

Typhoon Morakot brought heavy rainfall in 2009 and initiated many landslides and debris flows, including in the Chishan River catchment, one of the tributaries of the Kaoping River. In this study, we report on the identification of landslides and debris flows using GIS based on the digitization of ortho-rectified aerial photos. More than 10,216 landslides and 140 debris flows were identified caused by heavy rainfall during the typhoon. Features identified as mass movement landforms were then mapped onto a 500 m grid using Getis-Ord Gi* to indicate the location of landslide concentration areas or ‘hotspots’. There were significant effects on the local population due to loss of life and migration out of the affected areas. A government scheme to relocate people affected by the Typhoon Morakot landslides and debris flows was instigated in order to prevent further problems from hazards of this sort. Post-event evacuation is possible but it is recommended that the government and non-government organizations work together to ensure more effective mitigation of future typhoon hazards.