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Department of Rangeland and Watershed Management, Faculty of Natural Resources , Yazd University, Yazd, Iran
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Introduction and Objective: It is necessary to know the spatial relationships between upstream vegetation and sedimentation in the basins for optimal control and management of water and soil resources.The present study was conducted with the aim of determining the relationship between vegetation cover and suspended sediment concentration in the two watersheds of Doab Mareg and Gamasiab.
Material and Methods: At first, in order to investigate the correlation between the spectral reflectance of the Sentinel-2 image bands and the sediment concentration, the suspended sediment concentration statistics of the Doab Mereg station, located in the Qarasu river, and the Polchehr station, located in the Gamasiab river, were used simultaneously in a five-year period (2016 to 2020). Next, the Normalized Difference Vegetation Index (NDVI) for the two seasons of May and June was extracted using Sentinel-2 images, and the relationship between vegetation cover and suspended sediment concentration recorded at the station and extracted from the images was estimated separately.
Results: The results of the correlation analysis of suspended sediment concentration showed that the best result for the Doab station was related to band 4 (R2=0.86), and for the Polchehr station, it was related to band 5 (R2=0.83). The best values of the coefficient of determination (R2) of the normalized vegetation cover difference index were obtained for the two Doab and Polchehr stations, 0.98 and 0.64, respectively, which indicates that the amount of sediment decreases with the increase in vegetation cover. The average values of the vegetation index for the Mart watershed are equal to 0.35, and for the Gamasiab watershed, it is equal to 0.28, which shows the relatively thin vegetation of the area. The lowest average value of vegetation cover in the studied season (spring) was found to be 0.11 in the Margh watershed in June and 0.21 in the Gamasiab watershed at the end of May.
Conclusion: The existence of an inverse and close relationship between the average vegetation index (NDVI) and sediment indicates the positive effect of vegetation on soil protection and reducing the production and transport of sediment within watersheds. In general, the results showed that vegetation has been effective in the quantity and quality of spatial changes in the sedimentation rate of the basins, and the NDVI vegetation index as a representative of vegetation can be successfully used to create a statistical model of the changes in the sedimentation rate. Additionally, revitalization of vegetation should be included in development plans.
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Type of Study: Research | Subject: سنجش از دور و سامانه های اطلاعات جغرافيايی
Received: 2023/12/3 | Revised: 2024/01/19 | Accepted: 2024/01/20

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