Monitoring the speeds of migrating dunes and the volumes of sand transported over time is important to understanding how arid landscapes respond to wind-driven changes.
Traditionally, scientists have monitored such changes through detailed field surveys or long-term surveillance of stakes planted in dune fields. Vermeesch and Drake have developed a new and more convenient approach to monitoring the speed and sand flux of migrating dunes.
By using pairs of high-resolution optical satellite images taken at differing times, the authors monitored dune migration in the Bodélé depression of northern Chad over time intervals of 1 month to 6.5 years.
The displacement maps generated from each pair of satellite images were then used to automatically distinguish dunes from interdunes. By interpolating a surface between the interdune areas and subtracting it from the surface observed by the satellite images, the authors obtain dune heights and volumes over fine spatial and temporal scales.
From this, pixel-by-pixel estimates of sand flux were generated, allowing the authors to confirm that the Bodélé contains some of the world's fastest moving dunes.
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