Coupling leeside grainfall to avalanche characteristics in aeolian dune dynamics
journal contributionposted on 06.01.2017, 10:53 authored by Joanna M. Nield, Giles F.S. Wiggs, Matthew BaddockMatthew Baddock, Martin H.T. Hipondoka
Avalanche (grainflow) processes are fundamental drivers of dune morphodynamics and are typically initiated by grainfall accumulations. In sedimentary systems, however, the dynamism between grainfall and grainflow remains unspecified because simple measurements are hampered by the inherent instability of lee slopes. Here, for the first time, terrestrial laser scanning is used to quantify key aspects of the grainfall process on the lee (slip face) of a barchan sand dune. We determine grainfall zone extent and flux and show their variability under differing wind speeds. The increase in the downwind distance from the brink of peak grainfall under stronger winds provides a mechanism that explains the competence of large avalanches to descend the entire lee slope. These findings highlight important interactions between wind speed, grainfall, and subsequent grainflow that influence dune migration rates and are important for correct interpretation of dune stratigraphy.
This study was funded by National Geographic Society Science and Exploration Europe (GEFNE110-14), British Society for Geomorphology and NERC GEF )1025) grants.
- Geography and Environment