Megalake Chad : New Insights from Topographic Data

Abstract

Once roughly five times the size of the Lake Superior in the United States, Megalake Chad was a vast inland lake that has drastically receded over the past 5,000 years, leaving behind geomorphic features and drainage patterns indicative of its former expanse. This study investigates the geomorphic features and hydrology of this ancient lake using topographic data. Specifically, we utilized the Shuttle Radar Topography Mission (SRTM) 30-meter Digital Elevation Model (DEM) for analyses, generating slope maps to enhance our understanding of surface drainage patterns. To identify drainage features potentially overlooked by slope analyses, radar remote sensing data was used. Because much of Megalake Chad's northern basin is in the Sahara Desert radar sensors like PALSAR and RADARSAT are valuable for their ability to reveal subsurface features under the sand. Integrated topographic surface analysis and subsurface mapping offers a promising approach to uncovering buried channels and alluvial fans/deltas. Our findings not only reinforce evidence of a large ancient lake, but also reveal previously underexplored drainage patterns with potential valuable water resources and arable land.