Seasonal Analysis And Quantification Of Sand Dune Dynamics In The Ternata Oasis (Middle Draa, Morocco) Using Topographic Surveys and GIS

Abstract

This study focuses on the seasonal analysis and quantification of the morpho-sedimentary dynamics of transverse dunes in the Ternata oasis (Morocco) It is based on an integrated methodological approach that combines topographic surveys conducted using a LEICA TS 02 total station, along with spatio-temporal data processing and analysis using GIS software. The primary objective was to monitor the morphological evolution of the dunes over the four seasons of the year 2023. Descriptive and cartographic approaches also contributed to refining the understanding of the internal dynamics of these aeolian forms. The results highlighted a general trend toward accumulation, evidenced by a notable increase in the volume and surface area of the two dunes analyzed. Regarding dune mobility, the topographic measurements revealed differentiated displacements depending on the orientation of dominant winds and local topographic constraints. These spatial and directional divergences underscore the combined influence of wind regimes, geographic positioning, and the geometric characteristics specific to each dune. Moreover, the seasonal analysis revealed a contrasting dynamic marked by strong morpho-sedimentary variability. Dune nº 1 displayed an unstable evolution, with a significant volumetric increase until summer, followed by a sharp decline in autumn—reflecting an alternation between dominant erosional phases (spring–summer) and accumulation phases (autumn). Dune nº 2, on the other hand, exhibited a more extreme dynamic, with a volumetric peak in summer that is rapidly reversed in autumn, indicating its heightened sensitivity to wind activity.