Assessment of Desertification in Settlements of Qazvin Plain Using Sentinel-2 Images, Spectral Indices and Desertification Divided Indexx (DDI)

In this study, Sentinel-2 images have been used for the quantitative assessment of desertification in Qazvin Plain. First, topsoil grain size index (TGSI), albedo, normalized difference vegetation index (NDVI) and modified soil adjusted vegetation index (MSAVI) were extracted. Next, for linear regression, different combinations of indices were considered and Pearson correlation was established between NDVI and albedo, MSAVI and albedo, TGSI and albedo, TGSI and MSAVI. Then, using the NDVI-albedo and MSAVI-albedo regression, Desertification Divided Index (DDI) was estimated. Finally, the map of desertification was drawn for the study area in five classes of very severe, severe, moderate, low and very low. The study found that albedo was negatively correlated with MSAVI and NDVI indices but positively correlated with TGSI. The strongest correlation was between MSAVI and albedo (-0.417), while the weakest was between albedo and TGSI (0.33). According to DDI, the desertification situation in the region has been in the alarming range. In fact, by testing albedo with MSAVI in 2018, 2.4% of the region was classified with very severe desertification, while 21.7% had very low desertification. According to albedo-NDVI, 18.51% of the region had very severe desertification. In 2023, the first value increased to 10.3% and the second decreased to 5% indication remarkable rise in desertification in five years.