Evaluation of spatio-temporal variations of sand dunes surface using time series satellite observations of Landsat imageries (Case study: Rig-Zarin)

Sand dunes are always moving due to various variables such as wind, sediment grain size, humidity, topography, morphology of hills and vegetation coverage. The purpose of this study is to investigate the amount of displacement of the Rig-Zarin surface in the northwest of Yazd city. To assess the changes and developments of the sand dunes, time series satellite observations of Landsat TM were utilized from 1977 to 2017. The results showed that the area of the sand dunes fluctuated during this time period, while increased in some time and decreased at another times. Nevertheless, the overall process of changes was incremental during the whole period, and the surface of the sand dunes has developed about 60 Km2. The results also showed that in the two periods of time, from 1987 to 1993, as well as from 1998 to 2002, the area has decreased. In addition, the gradient of the incensement of area has not been the same and in some intervals the increase has been much more impressive. But, from 2002 to 2008, the increscent of area was less than 2Km2 which are associated with increasing or decreasing soil moisture content. In the moist years, there is no possibility of area development, and the sand dune is compressed, so its surface has been reduced. But in droughts, especially in the last 10 years, the development of the surface area of the Rig-Zarin was considerably impressive (about 30 Km2). Also, the results showed that the direction of movement has always changed.