Estimation of dune migration rates north Riyadh City, KSA, using SPOT 4 panchromatic images

• Irq Al-Rethma is a north-south small sand sea developed in the ridge-and-valley landscapes in the eastern province of KSA.
• The Irq comprises old stable dunes and sand sheets superimposed by recent active barchan and transverse dunes.
• The COSI-Corr technology has been conducted on SPOT 4 panchromatic images to measure dune migration rates and directions.
• The annual average dune migration rates of recent active dunes ranged from 1.6 to 2.25 m/yr.
• The migration direction of active dunes is the southern direction in response to dominant northern wind in the study area.

Irq Al-Rethmah is located north of Riyadh City, KSA, as elongated NW-SE sand accumulations. Its formation and development are highly controlled by the ridge-and-valley landscape dominant in the east of Saudi Arabia. The active dunes of Irq Al-Rethmah are basically represented by barchan and transverse dunes. These active dunes either superimpose the old stable dunes and sand sheets or directly occur over the alluvial plain adjacent to the western reaches of old stable dunes. The Co-registration of optically sensed images and Correlation (COSI-Corr) technology was conducted on two SPOT 4 panchromatic images acquired in 2006 and 2009 respectively to determine the migration rates and direction of the active dunes. The average annual migration rates of active dunes ranged from 1.6 to 2.25 m/yr. The migration rates decrease where the active dunes superimpose the old stable dunes and sand sheets. On the other hand, these rates increase when the active dunes are located over the alluvial plain along the western margins of Irq Al-Rethmah. The calculated vector displacement field by COSI-Corr technology suggest a southward direction of dune migration indicating that the predominant wind direction is northerly. Although the calculated rates are generally low in comparison to other measured migration rates of sand dunes in the east of Saudi Arabia, the spatial analysis implies potential hazards of active dunes against many landuse components such as roads, powerlines, and recreational facilities in the study area.