Grainflow shape quantification and classification

Keywords: Avalanche, Dune Migration, Morphology, Aeolian Processes
Session Type: Virtual Paper Abstract
Day: Tuesday
Session Start / End Time: 3/1/2022 11:20 AM (Eastern Time (US & Canada)) - 3/1/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 18

Abstract

Grainflow, or avalanche, is one of the main sediment transport processes on the slipface of a dune. Processes associated with gravity-driven grainflow have been subjects to several field studies. Relatively little is known, however, about grainflow morphology. Grainflow morphometric characteristics may be a key to revealing the complex morphodynamics of a dune slipface. As it is suggested by Boyce and Clark (1964) that shape features of an object may indicate answers for its associated complex dynamical mechanisms. Therefore, it is important to analyze and classify the morphometric attributes of grainflows. But there is no agreement on how best to characterize and quantify grainflow morphology. To avoid manual measurement and different assumptions or definitions on grainflow dimensional attributes, 11 dimensionless shape attributes are automatically calculated to characterize grainflow shape features. After a preliminary correlation analysis and principal component analysis to identify underlying variables that explain the pattern of correlations within these shape indices, four shape attributes are used to quantify and classify grainflow shape characteristics. Then, K-means clustering analysis is conducted to group similar shape features together. Finally, four types of grainflows are distinguished, compact rectangular grainflows, elongated triangular grainflows, rectangular shaped grainflows, and compact triangular shaped grainflows. This is the first and objective quantification on grainflow morphometry, which provides the foundation for form and aeolian process on a slipface. The classified shape features will further facilitate shape comparison and morphodynamics studies on a dune slipface from different terrestrial and extraterrestrial aeolian environments and interpretation on dune evolution mechanisms.