Abstract
AbstractGrain flows are an integral part of sand dune migration; they are a direct response to the local wind regime and reflect complex interactions between localized over‐steepening of a dune slipface and complex turbulent airflow on the lee slope. Grain flows are primarily responsible for delivering sediment to the base of a dune, thus driving slipface advancement; yet, there are few constraints on their morphological and spatial characteristics or the amount of sediment that is redistributed by these flows. Using a combination of high‐resolution terrestrial laser scanning and video recordings, four distinct grain‐flow types are identified based on morphology and area on a dune slipface. Grain‐flow morphologies range from small, superficial flows to larger flows that affect greater portions of the slipface, moving significant amounts of sediment. Detailed field observations are presented of the dynamics of lee slopes, including measurements of the initiation location, thickness, magnitude and frequency statistics of grain flows, as well as volume estimates of redistributed sediment for each grain flow observed. High‐resolution laser scans enable accurate quantification of bulk sediment transfer from individual grain flows and can be used to study grain flows in a variety of environments. A categorization of grain‐flow morphologies is presented that links styles of flows with wind strength and direction, turbulent airflow, sediment deposition and environment.
Highlights
Grain flows, or avalanching, on aeolian dunes is an essential process in dune migration
There is a need for additional field observations, wind tunnel experimentation, and numerical modelling over a wide range of aeolian settings and dune morphologies, as well as a classification system of grain flows to begin constraining spatial, morphological and dynamic characteristics of grain flows
This study presents the foundation of a classification system which can be used by future studies to describe grain-flow attributes observed in the field or during wind tunnel experiments and can be used to compare grain-flow behaviour between a variety of environments
Summary
Avalanching, on aeolian dunes is an essential process in dune migration. Grain flows have been the focus of many studies including in situ observations of active dunes, interpretations of flow signatures and paleoenvironments in aeolianites, wind tunnel experiments, and numerical modelling approaches. Despite these studies, there is still a lack of knowledge regarding grain-flow formation, initiation, magnitude, flow morphologies, and behaviour under a variety of wind conditions and environments There is a need for additional field observations, wind tunnel experimentation, and numerical modelling over a wide range of aeolian settings and dune morphologies, as well as a classification system of grain flows to begin constraining spatial, morphological and dynamic characteristics of grain flows. This study presents the foundation of a classification system which can be used by future studies to describe grain-flow attributes observed in the field or during wind tunnel experiments and can be used to compare grain-flow behaviour between a variety of environments
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