Challenges in aeolian geomorphology: Investigating aeolian streamers

摘要

This paper reviews the challenges involved with instrumentation, data acquisition, analysis, and the application of theory when conducting field experiments in natural aeolian environments. This is presented in the context of a field investigation into the formation and behaviour of aeolian sand streamers. Also known as sand snakes, streamers are a familiar manifestation of pronounced spatial and temporal variability in wind-blown sand over beaches, dunes, and other sedimentary surfaces. Streamers represent complex and dynamic transport patterns that change over temporal scales on the order of 0.1 s and over a range of spatial scales from 0.1 to 10 m. These transport features are likely governed by near-surface turbulent structures in the wind, necessitating detailed measurements of turbulence dynamics in association with sediment transport patterns. This paper reviews all stages of the investigation, from field site selection to the evaluation of theoretical models. The discussion covers a range of topics, including: research strategy, site selection, instrumentation requirements and limitations, experimental design and measurement techniques, scale and precision of data acquisition, data processing and visualization, description and parameterisation of results, challenges of spatio-temporal data analysis, turbulence measurements in the saltation layer, scaling issues and non-dimensionalisations in fluid dynamics theory, and the application of theory and conceptual models to the complexities of real natural environments. The challenges discussed here apply to many geomorphological field investigations in general, and three principal issues are identified: 1) the need for inexpensive, compact, and robust instruments with high spatio-temporal resolution, 2) the lack of extended quantitative methods for the computational analysis of shapes, forms and patterns, and 3) the conceptual discrepancies and ambiguities of applying scaling parameters from experimental engineering and idealized theoretical models to complex natural geomorpohic systems.