Drumlins This website is part of a project funded by the Natural Environment Research Council of the UK which focuses on testing the instability theory of subglacial bedform production. You are here Home Drumlins About the project Transverse sand ripples formed on a river bed arising from an instability in the coupled flow of water and sand. Note that two wavelengths of bedforms exist presumably resulting from different flow stages of the river. Instability theory Definitions Drumlins Flutes Nigardsbreen glacier, Norway. Credit: Dr Darrel Swift. Subglacial bedforms Ribbed or rogen moraines Mega-scale glacial lineations (MSGL) Crag-and-tail