Evaluation of part of the Mekong River using satellite imagery

Large rivers of the world are difficult to investigate. This is essentially due to the logistical problems involved when attempting to study rivers that are about a thousand kilometres or more in length and drain basins of appropriate dimensions. This creates difficulties in river management and also in determining the possible impact on the river system of specific development projects or basin land-use changes. We demonstrate the capability of satellite images, a huge number of which are currently archived in various centres around the world, to provide at least a coarse-scale solution to these problems. A significant amount of work can be done even without the application of any special remote sensing technique. About 14,000 km(2) of the middle Mekong Basin in Lao PDR has been studied. The Mekong is the 12th longest river in the world and is ranked eighth in terms of mean discharge. The Mekong is worth investigating for several reasons. (1) It has a fascinating and complicated physiography. (2) Little published information exists for the basin, at least for the part selected for the case study. (3) Various development plans have been drawn up for the Mekong with possible environmental impact on the basin and the river. The images are used in conjunction with the limited geomorphic and hydrologic data available in order to (1) provide a concise account of the local geomorphology, (2) map environmental degradation and sediment transfer in parts of the basin and (3) determine the nature of possible environmental impact associated with certain proposed development projects on the river. This is carried out by searching through the SPOT satellite images archived at the Centre for Remote Imaging, Sensing and Processing (National University of Singapore), selecting and studying clear scenes, and comparing the 1996, 1998 and 1999 images of the study area to record changes over time. Primarily, the study is a demonstration in combining remote sensing and geomorphology for environmental management of a large river system. It is also a plea for transforming the satellite images accumulating in various archives to useful geomorphological databases. Given the scale of large rivers, satellite images are excellent tools for their investigation. (C) 2002 Published by Elsevier Science B.V.