Analyzing the Eustatic and Geostatic Changes in the Stability of the Caspian Coastal Plain (Case Study: Chalus)

جغرافیا و مخاطرات محیطی

Volume 14, Issue 2 - Serial Number 54, June 2025, Pages 266-286   

Document Type: Research Article

DOI: 10.22067/geoeh.2024.88908.1501

Authors

Mohammad Fathollahzadeh¹; Mojtaba Yamani^{* 2}; Abolghasem Goorabi³; Mehran Maghsudi²; Mehrnoosh Ghadimi³

¹PhD Student in Geomorphology, Faculty of Geography, University of Tehran, Tehran, Iran

²Professor in Geomorphology, Faculty of Geography, University of Tehran, Tehran, Iran

³Associate Professor in Geomorphology, Faculty of Geography, University of Tehran, Tehran, Iran

Abstract

A series of large-scale and long-term environmental processes, including seismic events, construction activities, land use changes and groundwater extraction, along with climate changes in low-lying coastal areas can lead to deformation, land surface and topographic instabilities. Coastal deltas are part of the landforms and landscapes that, due to the proximity of both land and water environments, leave visible effects against tectonic activities, which are related to things such as changing the pattern and place of formation of deltas due to the change in the course of coastal rivers, the formation of unbalanced coastal terraces in parts of The coast and the emergence of cut beaches in the form of sea loads can be mentioned. In this research, we investigated the geomorphic changes of the coastal plain of Chalus due to eustatic and geostatic activities and their effects on the changes of the plain and coastline in the Chalus region, the results obtained from radar processing, geodynamic data, changes in the level of underground water, geostatic activities, The eustatic changes of the Caspian Sea and the changes in land use show that the Chalus plain has risen under the influence of geostatic activity in the past two decades, and on the other hand, the Chalus coastline has moved towards the sea as a result of the changes in land use and the increase in river sediment load and the decrease in the level of the Caspian Sea. It has been significant that its result is significant in terms of environmental and economic damages.
 EXTENDED ABSTRACT
Introduction
Environmental transformations, including tectonic activities, climate change, excessive groundwater extraction, and land use changes, significantly impact the stability of coastal plains. Due to its strategic location along the Caspian Sea, the Chalus Plain is affected by geostatic changes (including tectonic and seismic activities) and eustatic changes (related to sea level fluctuations). This study examines the impact of these changes on the stability of the Chalus coastal plain.
Material and Methods
This research utilizes radar remote sensing techniques (specifically SBAS and PS InSAR), geodynamic data, Sentinel-1 and Landsat satellite images, GNSS data, and groundwater level measurements. The data, collected between 2017 and 2024, were analyzed to assess surface displacement, groundwater fluctuations, shoreline changes, and land use transformations.
Results and Discussion
Geostatic Changes and Ground Displacement: InSAR analysis revealed that the Chalus Plain has primarily experienced uplift over the past decades, with an average displacement of +2 to +8 mm per year. Geodynamic data confirmed that tectonic and seismic activities associated with the Khazar and Alborz North faults are the main drivers of this displacement. Impact of Caspian Sea Eustatic Changes: Satellite data analysis indicated that the Caspian Sea level dropped by approximately 2.1 meters between 1992 and 2024. This decline resulted in a shoreline advance of 22 to 385 meters, with the most significant changes occurring at the Chalus River delta and the Nowshahr Port area. Role of Land Use Changes: Satellite imagery analysis showed a notable reduction in forest cover and an increase in bare land and built-up areas over the past 23 years. These changes have led to increased surface runoff, accelerated soil erosion, greater sediment loads in the Chalus River, and subsequent delta expansion and shoreline advancement.
Conclusion
The findings indicate that the Chalus Plain has undergone significant geostatic and eustatic changes. Tectonic activities have caused land uplift, while sea level decline and increased river sediment loads have contributed to shoreline expansion. To mitigate the adverse effects of these changes, the following measures are recommended: reforestation and vegetation restoration in the Chalus watershed to reduce erosion and sedimentation; diplomatic efforts to secure Caspian Sea water rights from upstream countries (e.g., Russia); and effective land use planning to prevent unregulated urban expansion along the coast. This study underscores the importance of integrated coastal management and the need for continuous monitoring of geological, hydrological, and land use changes to ensure the sustainability of coastal plains. 




 

Keywords

Caspian Sea Coastal Plain; Eustatic Sea Level Changes; Geostatic Land Deformation; Radar Interferometry (InSAR)

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