Abstract
Sand accumulations northwest Al-Lith City, Saudi Arabia, comprise transverse and barchan dunes. These dunes are located either in association with the major valleys, adjacent to mountain fronts, or as individual small dunes scattered over the wide coastal plain. To determine the magnitudes, directions, and the spatial variabilities of dune migration in the study area, two SPOT 4 panchromatic satellite images have been acquired in April 8, 2010 and August 16, 2010 for the master and the slave images, respectively. The COSI-Corr technology has been used to precisely ortho-rectify and co-register the acquired satellite images for eventual correlation using fast Fourier transform correlation engine to produce east-west and north-west displacement bands. Both bands were used to produce the net pixel displacement and vector displacement field that demonstrates the direction of the migration. The highest net displacement values were limited to the areas occupied by sand dunes and ranged from 0.0 to 17.9 m/month with an average of 1.30 m/month. The produced net displacement map indicated high spatial variabilities of the magnitudes of dunes migration rates throughout the study area. The migration rates of individual barchan dunes over the coastal plain ranged from 1.5 to 12.3 m/month with an average of 4.7 m/month. In a small barchan dunes adjacent to a mountain front, the migration rates of barchan dunes decreases which ranged from 0.5 to 1.7 m/month with an average of 1.0 m/month. In a small field of transverse dunes, the migration rates ranged from 0.9 to 3.9 m/month with an average of 4.5 m/month. Along with the determination of the migration rates, the directions of dune migration have been determined as well. The vector displacement field indicated that the principal directions of dunes migration are E and SE directions referring to the influence of the prevailing wind directions in the western region of Saudi Arabia. Studying the relationship between the magnitude and direction of dune migration and the spatial locations of the various landuse elements indicated that many of these elements are under a direct risk of dune migration.