Impacts of the Wenchuan Earthquake on the Chaping River upstream channel change

The Wenchuan Earthquake, measuring magnitude 8.0 on the Richter scale, occurred on 12 May 2008 in Sichuan, southwest China and caused over 87 000 casualties. Geological disasters such as debris flows and landslides caused by the Wenchuan Earthquake were severe. Several high-risk dammed lakes formed in the Chaping River basin of An’xian County, Sichuan, China, which is located in the earthquake zone, caused great changes in river morphology and brought great danger to the people and properties in the river downstream. Channel change information from different periods was important to risk relief of dammed lakes and assessment of losses. A Satellite Pour l’Observation de la Terre 5 SPOT 5 fused image of 10 November 2006 with 2.50 m spatial resolution, and unmanned aerial vehicle UAV images of 19 May 2008 and 23 December 2008 with 0.32 and 0.33 m spatial resolution, respectively, were applied to derive channel information in the Chaping River upstream from three periods pre-disaster, during the disaster and post-disaster using an object-oriented classification method with an edge-based segmentation algorithm and a support vector machine SVM classifier. Geological landslides and dammed lakes from different periods were analysed. Based on the channel information from different periods, channel changes were determined, and impacts of the earthquake on channel area, channel width, river morphology, and so on were discussed.