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

Abstract

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 subenvironments 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.

A classification scheme for fluvial–aeolian system interaction in desert-margin settings

“…Significant diversity in the arrangement and type of interaction of competing depositional sedimentary systems is recognised in modern desert dune fields and their marginal areas, and these give rise to complex yet predictable geomorphological patterns that commonly vary over space and time (e.g. Lancaster, 1989;Cooke et al, 1993;Bullard and Livingstone, 2002;Al-Masrahy and Mountney, 2013). The record of these interactions is also recognised in the ancient sedimentary record (e.g.…”

Controls on sand ramp formation in southern Namibia

“…The mechanism controlling superimposition is debated with large‐scale changes in wind regime and climate (Warren and Allison, ), seasonal or annual variation in wind (Bristow et al, ), landscape patterning and self‐organisation (Ewing et al, ; Dong et al, ) and stabilisation of the underlying dune due to climatic change (Dong et al, ) all suggested as potential drivers. There is some evidence that the size of the dune determines the quantity and complexity of superimposed features with secondary features unable to form where the primary dune is below a certain size (Breed and Grow, ; Al‐Masrahy and Mountney, ). Thus, secondary dunes may simply be a function of airflow fluctuation created when the flanks of the dunes are large enough to form a planar surface (Lancaster, ).…”

Long‐term sand dune spatio‐temporal dynamics and endemic plant habitat extent in the Athabasca sand dunes of northern Saskatchewan

“…; Wood et al. ; Al‐Masrahy and Mountney ). Long‐term climatic data for the study were obtained from the Environment Canada – Fort Chipewyan (58°46” N; 111°07’“W) weather station located approximately 115 km south‐east of Athabasca dune fields, as this was the closest station with long‐term weather data available (Carson and MacLean ).…”