Document Type : Full length article
Authors
1
Assistant Professor of Geomorphology, Geography Department, Golestan University, Gorgan, Iran
2
M.A. in Environmental Hazards, Department of Geography, Golestan University, Gorgan, Iran
3
Assistant Professor of Geography Department, Golestan University, Gorgan, Iran
4
Associate Professor of Geology Department, Golestan University, Gorgan, Iran
Abstract
Extended Abstract
Introduction
The phenomenon of land subsidence involves the collapse or sinking of the earth's surface, which can also have a slight horizontal displacement vector. This movement is not limited in terms of intensity, extent, and measure of the involved areas. Subsidence in cities leads to costly and serious damage to urban infrastructures such as buildings, roads, and railway tracks. Land subsidence can occur for various reasons: groundwater abstraction, subsidence due to oil extraction in oil fields, displacement due to landslides, and collapse of internal walls of mines.
Interferometric Synthetic Aperture Radar (InSAR) is a powerful technique for measuring the topography of a surface and its changes over time. Varamin plain is one of the areas affected by subsidence in Iran, which is located in the alluvial fan of Jajrood river, and its development and prosperity is due to the quality and fertility of the soil in this region. Irregular and over pumping groundwater has caused many subsidence cases in the study area. This study investigates the subsidence of Jajrood alluvial fans with emphasis on Javadabad Varamin from 2016 to 2019, using the permanent scatter radar interferometry method.
Materials and Methods
In this study, 41 images of Sentinel (2016-2019) were used to determine the rate and amplitude of land subsidence using the method of permanent dispersants. Permanent scattering points (PS) were selected based on the domain scattering index.
According to the threshold limit, the amplitude scattering index is usually considered to be 0.4 or 0.42 in various studies, which means that all selected points are not located in the set of PS points, and only those points to be selected that the amplitude scattering index value is exceeding the threshold. Then, a points network (PS) was prepared at this stage to evaluate the processing performed. The prepared spatial network in this section is derived from the Delaunay model. Since the amount of displacement is relative in this method, one of the points in the area is selected where the amount of displacement is relatively zero compared to other points, and other PS points are applied to it. Because of seasonal temperature changes and their effect on buildings that cause elevation changes (the effect of temperature on the structure of buildings), the selected point must be located on the ground. SNAP software was selected for radar interferometry processing. In order to find the cause of subsidence, the information of piezo metric wells (1996-2016) in the study area and their temporal changes were investigated.
Results and discussion
research findings:
یافته های پژوهش:
The findings:
یافته ها:
Can't load full results
Try again
Retrying...
Retrying...
Can't load full results
Try again
Retrying...
Retrying...
In general, land subsidence has occurred in two significant areas. The northern region is located in the Jajrood alluvial fan. The length of this zone is 44 km, and its width is 7 km, which covers an area of more than 300 square kilometers.
The highest subsidence in this area is related to the Golabbas area, which is about 120 mm per year. The presence of Jajrood alluvial fan and agricultural lands in this area is considerable.
The second region is related to the southern zone. The northern part of this zone is bounded by the city of Pishva, Qala-e-Sin, and the east of Varamin city. In these areas, the annual subsidence rate reaches to maximum six cm. The southern part of this zone is surrounded by Hesargol and Jahanabad areas.
In these areas, the land subsidence rate is lower compared to the central areas and is about 20 to 40 millimeters per year. In the northern part of the Jahanabad region, the maximum land subsidence is 60 mm per year. The southern zone in which the study area is located has a circular shape, and the amount of land subsidence increases from the periphery to the center of the region. The highest rate of land subsidence in the study area occurred in Salman-Abad, Khaveh, Javadabad, Hesar-e-Sorkh, and Zavarehvar areas, with the amount of between 160 to 200 mm per year. Areas such as Tajreh, Rostamabad, and Hesar Kouchak also show significant land subsidence, about 120 to 160 mm per year.
Conclusion
Conclusion
نتیجه
the conclusion
نتیجه گیری
Can't load full results
Try again
Retrying...
Retrying...
Can't load full results
Try again
Retrying...
Retrying...
The result of radar interferometry studies has demonstrated that subsidence has occurred in the main parts of the Jajrood alluvial fan's surface. Javadabad region, which is located in Varamin is one of the areas with significant subsidence that subsidence occurs at rate of 20 cm per year Studies conducted in the study area depicted that the decreases in groundwater level in the study area is linear and this is acceptable in justifying land subsidence. So that the patterns obtained using the radar interferometry method in order to find the pattern of land subsidence and groundwater were consistent and somewhat uniform. In this regard, one of the main causes of land subsidence in the region in Javadabad due to the increasing depth of piezo metric wells in the study period can be attributed to the high pumping of groundwater resources.
According to the physiographic shape of the region and the pattern of land subsidence, the highest rate of land subsidence was observed in areas consisting of low slopes, including Javadabad and Varamin. In terms of risk, population, roads and buildings, railroads are involved in the phenomenon of land subsidence in this region. The railroads of Tehran, Mashhad, Garmsar and Qom are the connecting roads in this region.
Keywords