Examination of the role of Playa in formation of Yazd sand deserts

The source of sandy dunes has been the main question in desert regions. Several theories have been already presented about this question around the world. In addition, several methods have been already invented and applied to find the source of sandy dunes. In this research, the relationship between playa and sandy area in Yazd province was studied using GIS. At first, the maps of sand dunes and playa in the province as well as neighboring areas were produced. Then, the distance and direction of all sandy polygons to the nearest playa was calculated. Meanwhile, the geographic center of sandy polygons and playa polygons were identified. According to the results, around 60% of sandy polygons had a distance less than 10 kilometers to the playa, and their average distance to the nearest playa was calculated to be 12745 meter. In more than 79% of sandy dunes, the nearest playa was located in the North West. The average angle of playas to the sandy dunes was 332 degree (N), matching with the main windroses and sandroses of province. Therefore, if all sandy dunes and playas are converted to one place, we will have one sandy dune with an average area of 4717 hectares as well as a playa with an average area of 220506 hectares in the northwest of sand dune. Eventually, according to the prevailing wind direction, the hypothesis of the role of playas as the main source of sand dunes in the Yazd province is reinforced.