Mapping abandoned river channels in Mali through directional filtering of thematic mapper data

Abstract

The Inland Niger Delta of Mali is composed of an anastomosing channel network flowing northward across the Sahel to Tombouctou, where the distributaries converge and the Niger changes course to flow eastward. Processing of Landsat digital TM data to extract high frequency information reveals morphologic elements of a former northward continuation of the anastomosed system into the Saharan Azaouad Depression, and confirms prior northward, internal drainage of the Niger River. Morphologic relationships between the channels and semistabilized dunes of the Azaouad suggest that these channels were active as recently as 6000–8000 years before present.