Using Sentinel radar and optical data in the Google Earth Engine platform to determine the extent of land use changes in Alborz Province

Land cover (LC) maps play a key role in generating accurate data for land resource management. The recent developments in accurate data utilization as well as novel technologies and methods have led to the generation of valuable information useful in extracting remote sensing datasets for application in different fields. In this study, use was made of high-resolution satellite images and up-to-date methodologies to assess LC changes over five-year periods in Alborz Province. To achieve this, LC maps of the study area with the four major land classes of barren, cultivated, and built-up lands as well as water bodies were generated for the two time periods of 2009 and 2023 by combining optical and radar Sentinel images as well as such supplemental data as vegetation indices and Digital Elevation Model (DEM) using the random forest (RF) algorithm. For this purpose, 57 sentinel-2 and 15 sentinel-1 images were exploited for the first time period and 78 Sentinel-2 and 23 Sentinel-1 images for the second within the Google Earth Engine (GEE) cloud computing platform. The overall accuracy values obtained for the two periods were 92.4% and 94.5%, respectively, while the corresponding Kappa coefficients were 0.89 and0.9. The results showed a decrease of 29.38 KM2 in cropland and an increase of 21.4 KM2 in Built-Up areas over the past five years. Additionally, barren lands increased by 2.6 KM2 over the five-year period, with these changes primarily associated with the southern plains of the study area, which had changed from cultivated to barren land during the second period. In order to determine the trends in increasing built-up areas, the urban land map of the second period was laid on the land use classification obtained for the first period, whereby the extent of changes in each class was determined. The results showed that approximately 55% of the Built-up development had occurred on croplands, indicating a change of 11.74 KM2 of the cultivated land into Built-pp one. Hence, cropland loss in favor of human built-up land forms a major challenge in IRAN . Obviously, the maps thus prepared might serve as great contributions to land management thereby controlling the growth of human built-up lands, especially in the outskirts of metropolises.