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Volume 41, Issue 1 (2026)
GeoRes 2026, 41(1): 1001-1010 |
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History
Received: 2026/05/6 | Accepted: 2026/05/19 | Published: 2026/04/30
Received: 2026/05/6 | Accepted: 2026/05/19 | Published: 2026/04/30
How to cite this article
Ebadi L, Baghani A. Forty-Year Monitoring of Gorgan Bay Surface Area (1986–2025) Using Landsat Satellite Imagery and Its Relationship with Caspian Sea Level Fluctuations. GeoRes 2026; 41 (1) :1001-1010
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Abstract (145 Views)
Aims & Backgrounds: In light of the alarming desiccation trend of Gorgan Bay, the primary objective of this research is to conduct long-term monitoring of the bay's water surface area changes over a 40-year period (1986–2025) and to investigate the determining roles of Caspian Sea level (CSL) oscillations and precipitation in the Qarasu watershed on these morphological variations.
Methodology: This study utilized a time series of 36 Landsat satellite images. For precise water body extraction, the Modified Normalized Difference Water Index (MNDWI) was applied. To evaluate the accuracy of the area results, a classification map was generated from a Sentinel-2 image using the Support Vector Machine (SVM) method, followed by error matrix calculations. Water level data were retrieved and harmonized by integrating Baku station records with the DAHITI database. Additionally, precipitation data for the Qarasu basin were obtained from the CHIRPS database. Statistical analyses, including Pearson correlation and significance levels, were performed using MATLAB.
Findings: The results revealed that the bay's area decreased from a maximum of 565.48 km² in 1995 to a record low of 275.12 km² in 2023, indicating a loss of over 50% of its peak extent. Statistical analysis demonstrated an exceptionally strong, positive, and direct correlation between the sea level and the bay’s surface area (r = 0.9419; p < 0.001). In contrast, the relationship between watershed precipitation and the bay's area was not statistically significant (r = 0.2121; p = 0.2142).
Conclusion: Due to its shallow depth and gentle bed slope, Gorgan Bay serves as a sensitive indicator of the Caspian Sea level status. The findings emphasize that local atmospheric inputs cannot compensate for the coastline retreat driven by the sea level drop. Therefore, to prevent total desiccation, implementing environmental adaptation policies and integrated watershed management is an unavoidable necessity.
Methodology: This study utilized a time series of 36 Landsat satellite images. For precise water body extraction, the Modified Normalized Difference Water Index (MNDWI) was applied. To evaluate the accuracy of the area results, a classification map was generated from a Sentinel-2 image using the Support Vector Machine (SVM) method, followed by error matrix calculations. Water level data were retrieved and harmonized by integrating Baku station records with the DAHITI database. Additionally, precipitation data for the Qarasu basin were obtained from the CHIRPS database. Statistical analyses, including Pearson correlation and significance levels, were performed using MATLAB.
Findings: The results revealed that the bay's area decreased from a maximum of 565.48 km² in 1995 to a record low of 275.12 km² in 2023, indicating a loss of over 50% of its peak extent. Statistical analysis demonstrated an exceptionally strong, positive, and direct correlation between the sea level and the bay’s surface area (r = 0.9419; p < 0.001). In contrast, the relationship between watershed precipitation and the bay's area was not statistically significant (r = 0.2121; p = 0.2142).
Conclusion: Due to its shallow depth and gentle bed slope, Gorgan Bay serves as a sensitive indicator of the Caspian Sea level status. The findings emphasize that local atmospheric inputs cannot compensate for the coastline retreat driven by the sea level drop. Therefore, to prevent total desiccation, implementing environmental adaptation policies and integrated watershed management is an unavoidable necessity.
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