Environmental study of the middle Mekong Basin using multi-temporal SPOT imagery

The middle Mekong Basin in Lao PDR and Thailand with an area of about 13,969 sq km was investigated with SPOT data acquired from 1996 to 1999. The following digital image processing techniques were implemented in this study: generation of DEM, slope, aspect and orthorectified XS images, mosaic of the XS orthoimages, atmospheric correction and unsupervised change detection to create the thematic change map. Two significant changes were shown clearly by comparison of the images of 1996 and 1998/9: (1) marked depletion of vegetation from slopes, especially southern slopes, and (2) the bed of the river is choked with sediment, which is progressively silted up over time. This study demonstrated the application of remote sensing data for investigation of large river systems and for planning their management.