Remote sensing of spatial variability in aeolian dune and interdune morphology in the Rub’ Al-Khali, Saudi Arabia

The Rub’ Al-Khali aeolian sand sea of south eastern Saudi Arabia – also known as the Empty Quarter – covers an area of 660,000 km2 and is one of the largest sandy deserts in the world. The region is covered by the latest generation of public-release satellite imagery, which reveal spatially diverse dune patterns characterized by a varied range of dune types, the morphology, scale and orientation of which change systematically from central to marginal dune-field areas where non-aeolian sub-environments become dominant within the overall desert setting. Analysis of geomorphic relationships between dune and interdune sub-environments within 4 regions of the Rub’ Al-Khali reveals predictable spatial changes in dune and interdune morphology, scale and orientation from the centre to the outer margins of dune fields. A quantitative approach is used to characterize the complexity present where large, morphologically complex and compound bedforms gradually give way to smaller and simpler bedform types at dune-field margins. Parameters describing bedform height, spacing, parent morphological type, bedform orientation, lee-slope expression, and wavelength and amplitude of along-crest sinuosity are recorded in a relational database, along with parameters describing interdune size (long- and short-axis dimensions), orientation, and style of connectivity. The spatial rate of change of morphology of aeolian sub-environments is described through a series of empirical relationships. Spatial changes in dune and interdune morphology have enabled the development of a model with which to propose an improved understanding of the sediment system state of the modern Rub’ Al-Khali desert sedimentary system, whereby the generation of an aeolian sediment supply, its availability for aeolian transport and the sand transporting capacity of the wind are each reduced in dune-field margin areas.