LiDAR mapping of presumed rock-cored drumlins in the Lake Åsnen area, Småland, South Sweden

Abstract: The landform group called drumlins has since long been enigmatic; this study aims to shed some light on them. By mapping their extent in two areas around Lake Åsnen, Småland, southern Sweden, their extent and prop-erties have been mapped with a level of detail that would have been next to impossible just a few years ago. The method used in this study utilized LiDAR derived high resolution hillshade models to map out the drumlins extent and investigate whether any outcrops of bedrock could be identified inside their rim. The mapped data’s accuracy was then verified through a field survey. In total 201 drumlins were checked, 114 in the Vemboö area and 87 in the Torne area. The result showed that for the Vemboö area, 92.1%, and for the Torne area, 75.9%, of the drumlins were found to have a hard-core of bedrock. This indicates that it’s probable that the drumlins where no bedrock could be identified also most likely has one, but situated at some depth superimposed by till and other sediments. The method of mapping bedrock outcrops through hill shade models also proved accurate in more than 95% of the cases; this shows that this method is so reliable that it might be recommended for use over larger areas without the type of extensive field verification carried out in this study.