Early-stage aeolian protodunes: bedform development and sand transport dynamics
journal contributionposted on 2017-10-05, 14:04 authored by Matthew BaddockMatthew Baddock, Joanna M. Nield, Giles F.S. Wiggs
Early-stage aeolian bedforms, or protodunes, are elemental in the continuum of dune development and act as essential precursors to mature dunes. Despite this, we know very little about the processes and feedback mechanisms that shape these nascent bedforms. Whilst theory and conceptual models have offered some explanation for protodune existence and development, until now, we have lacked the technical capability to measure such small bedforms in aeolian settings. Here, we employ terrestrial laser scanning to measure morphological change at the high frequency and spatial resolution required to gain new insights into protodune behaviour. On a 0.06 m high protodune, we observe vertical growth of the crest by 0.005 m in two hours. Our direct measurements of sand transport on the protodune account for such growth, with a reduction in time-averaged sediment flux of 18% observed over the crestal region. Detailed measurements of form also establish key points of morphological change on the protodune. The position on the stoss slope where erosion switches to deposition is found at a point 0.07 m upwind of the crest. This finding supports recent models that explain vertical dune growth through an upwind shift of this switching point. Observations also show characteristic changes in the asymmetric cross section of the protodune. Flow-form feedbacks result in a steepening of the lee slope and a decline in lower stoss slope steepness (by 3°), constituting a reshaping of protodune form towards more mature dune morphology. The approaches and findings applied here, a) demonstrate an ability to quantify processes at requisite spatial and temporal scales for monitoring early-stage dune evolution, b) highlight the crucial role of form-flow feedbacks in enabling early-stage bedform growth, alluding to a fluctuation in feedbacks that require better representation in dune models, and c) provide a new stimulus for advancing understanding of aeolian bedforms.
- Social Sciences
- Geography and Environment
Published inEarth Surface Processes and Landforms
CitationBADDOCK, M.C., NIELD, J.M. and WIGGS, G.F.S., 2018. Early-stage aeolian protodunes: bedform development and sand transport dynamics. Earth Surface Processes and Landforms, 43(1), pp. 339-346.
- AM (Accepted Manuscript)
Publisher statementThis work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/
NotesThis is the peer reviewed version of the following article: BADDOCK, M.C., NIELD, J.M. and WIGGS, G.F.S., 2018. Early-stage aeolian protodunes: bedform development and sand transport dynamics. Earth Surface Processes and Landforms, 43(1), pp. 339-346, which has been published in final form at https://doi.org/10.1002/esp.4242. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.