جستجوی مقالات مرتبط با کلیدواژه "snap" در نشریات گروه "جغرافیا"

In arid and semi-arid regions, groundwater is more important for humans and ecosystems than surface water. Land subsidence is caused by the pumping and uncontrolled use of groundwater in an area. When the extracted quantities are not replenished by rainfall, it leads to damages such as road failures, destruction of residential areas, railways, as well as water and gas pipelines. The Yazd-Ardakan plain is one of the main plains in Yazd province, hosting 75% of the province's population density and most industrial centers. Additionally, this plain has been subjected to a ban by the Ministry of Energy due to a sharp decline in groundwater levels. This study aimed to quantify and compare the extent of subsidence using four Synthetic Aperture Radar (SAR) images of the C-band from the Sentinel-1 satellite and the radar differential interferometry method from 2017 to 2021. The maximum subsidence recorded in 2017 was 13 cm, while in 2020 and 2021, it decreased to 9 cm, primarily concentrated in the Shamsi region between Meybod and Ardakan. Furthermore, to validate the satellite-derived results, they were compared with those obtained through accurate leveling methods conducted by the Iran National Cartographic Center. The study revealed that Sentinel images exhibit a strong capability to estimate the extent of subsidence. Considering the examination of groundwater consumption and depletion statistics in recent years, potential reasons for the reduction in subsidence in the study area could be attributed to management measures such as water transfer to this basin, alterations in agricultural practices, and a decrease in groundwater depletion compared to previous years in this region.

The landscape of the earth's surface as a complex system is the result of the interaction of factors such as geographical, climatic, temporal processes and human activities. The physical development of cities, without observing the principles of urban planning and taking into account the potential of their natural hazards, leads to the high vulnerability of cities. One of the most important dangers in the plains and plains of our country is the dangers caused by land subsidence, which for various reasons, such as over-harvesting of underground water resources and climate changes, causes many problems for agricultural lands, roads, and transmission lines. has become power and energy; Therefore, it is very necessary to investigate the causes and to control and reduce its risks (Abedini et al., 1402). Groundwater is one of the most important sources of water needed by the agricultural, drinking and industrial sectors, especially in the dry areas of the central plateau of Iran. Therefore, investigating the process of its qualitative changes is very important in the sustainable management of water resources (Arshad Hosseini et al., 1400). . Yilaghi city of Shandiz, which is a part of Targaba Shandiz city, is 1400 meters above sea level and is located at 59 degrees and 17 minutes of latitude and 36 degrees and 23 minutes of latitude. This city is adjacent to the central part of Mashhad from the north, Targaba city from the south, Neishabur from the east and Golbahar from the west, and has an area of about 37,825 square kilometers. Since Shandiz Mashhad is known as one of the holiday areas of Khorasan and is surrounded by thick and dense vegetation of towering sycamore trees and flowing rivers and tourist attractions (Karizno Aqueduct, Shandiz Historical Tower, Shandiz Padideh, Cozy Cottage Garden, Panjan Nama, Park It is mountainous and...), has a cool and summery climate and is one of the main centers of travelers and tourists in Mashhad and all over Iran. All over the south of this city are the heights of the Binalud mountain range of Khorasan, and Shirbad peak in the Zashk region of Shandiz is also considered the highest point of this mountain range and Khorasan province.

In order to investigate the subsidence rate of Shandiz city and its relationship with the drop in the underground water level, first the rate of land subsidence in the period of 2016-2023 was calculated annually by radar interferometric method and then the trend of changes in the water level of piezometric wells during 29 years was investigated. took Finally, the research results were verified by field surveys. In order to process by radar interferometric method, SNAP software was selected to obtain the final results of the subsidence rate based on the phase difference between the images taken on different dates. In order to study the latest status of the groundwater level in the study area, the statistical information of piezometric wells from 1370 to 1399 was obtained from Razavi Khorasan regional water, which was then prepared in the GIS software after annual averaging using the IDW interpolation model to prepare the groundwater level map. and was evaluated.

In the investigations carried out with SLC radar images of Sentil 1 satellite in relation to the city of Shandiz, 8 images were processed two by two in the Snap software, the image of the year 2016 with 2017, 2017 with 2018, 2018 with 2019, 2019 with 2020 and 2020-2021, 2021-2022 and 2022-2023 images were checked and the amount of subsidence recorded for each period was 2 cm for 2016-2017, 6 cm for 2017-2018, 2 cm for 2018-2019, 5 cm for 2019-2020, for The 2020-2021 period was about 2 cm, 4 cm for the 2021-2022 period and about 1 cm for the 2022-2023 period. In the survey of the water level of Shandiz city from 1370 to 1399, the number of 2 main wells, Hassan Abad and Qasim Abad, which are located in the northeast and east of the city at a distance from it, were obtained with the same data, which information was obtained from the Khorasan Razavi Regional Water Organization. and was investigated. The data were averaged every 5 years and its maps were prepared using the IDW tool in the GIS environment for the study area. In the east of the region, the villages of Hesarsokh and Sarassiab were located in the area of high risk. The minimum and maximum water level drop in the 30-year period from 1370 to 1399 was calculated as 57.86 and 76.84 meters.

The results of interferometric studies showed that the amount of subsidence during 5 statistical periods in the studied area was 22 cm. The amount of subsidence recorded for each period is 2 cm for 2016-2017, 6 cm for 2017-2018, 2 cm for 2018-2019, 5 cm for 2019-2020, and 2 cm for 2020-2021. 4 cm for the 2021-2022 period and about 1 cm for the 2022-2023 period. According to the obtained results, the highest amount of subsidence has happened in the east, north and south of Shandiz from east to west. The water levels of the wells have reached their maximum decrease in the period from 1370 to 1399. The water level drop in this time period is at least 57.86 meters and the maximum is 76.84 meters, and all areas of Shandiz city have water level drops and are at risk. The subsidence has also covered most of the city areas. Shandiz city is a tourist area and all its geosites (Carizno Aqueduct, Shandiz Historical Tower, Shandiz Phenomenon, Cozy Cottage Garden, Finjan Nama, Mountain Park, etc.) are vulnerable to damage, therefore it needs special attention.

A subsidence is the collapse of land surface that may have a small horizontal displacement vector. This movement is not limited by magnitude, scope and extent of the areas involved. The Urban region 18 in South West of Tehran megalopolis has been developed. This study is conducted on radar interferometry, geotechnical analysis, piezometer wells analysis, and geomorphological effects. In the first step, images taken by Sentinel-1 data related to the years 2015 and 2017 were collected. size of subsidence obtained from radar interferometry was about 430 mm around Yaftabad and showed an increase from West to East and from North to South. Maps showing the distribution of gravel, sand were prepared using the geotechnical data within the depths of 5, 10, 15, 20, 25, and 30m. Study results show that the Particle size gets smaller in the region under study from North to South. in the Continuation, Examination of geomorphological effects revealed that as the urban region 18 is located on young alluvial fan of Kan, which contains high gravel distribution and porosity in lower depths, and as the depth of wells in the area indicate thick alluvium, water table decline, emptied pore space and as a result increased alluvium weight along the direction of gravity may increase the compression force and justify the subsidence phenomenon. next a map of phreatic surface was first prepared and then water table of area under study was compared over a period of 14 years. The phreatic surface map indicated that its level has been decreased from North to South. It also showed that the  water level of piezometric wells has been declined from West to East. Comparison of the water table over a period of 14 years revealed an average decline of 13 meters. The maximum water table decline in the area under study was related to the Northern part with 33 meters fall. The Eastern part of the urban region 18 is highly influenced by the subsidence phenomenon. Study results showed a relationship between the size of subsidence and areas with fine-grained soil. About 30 Km of main roads in the region are highly influenced by the subsidence phenomenon. railway of Tehran-Tabriz and the subway line 3 are important elements of transportation in region 18 which Length more than 12 Km over zones influenced by the subsidence phenomenon.

One of the risks that has occurred in many areas in recent years is the risks of subsidence. Iran's geographical location has caused many of its areas to be at risk, including the Pakdasht plain on the southern slopes of Alborz. Due to the importance of the subject in this study, the amount of subsidence in Pakdasht urban area has been evaluated. In this study, radar interferometry and Sentinel imaging were used to evaluate the subsidence of the area. For process information, SNAP and Snaphu software have been used to calculate the vertical displacement of the study area from 2018/01/08 to 2019/01/15. The results of the study indicate that the study area is lacking geomorphological barriers, in recent years, it has faced the trend of development of construction as well as the development of industrial and agricultural activities, which has led to increased exploitation and severe groundwater loss in the study area. Groundwater depletion has also caused a subsidence in the region so that, based on the results of radar interferometry, limited studies have been conducted within the 15 to 85 mm subsidence period over the 1-year period. Assessment of the displacement map of the area indicates that the highest amount of subsidence was in the western regions and the lowest in the southeastern areas of Pakdasht metropolitan area.

According to the US Geological Survey, the phenomenon of land subsidence involves the collapse or downward saturation of the earth that can have a slight displacement vector. Earth subsidence is a geological phenomenon that causes the earth to descend slowly and horizontally. This phenomenon is due to a variety of factors including natural factors such as earthquakes, volcanoes, fault activity, subsidence caused by sea level rise, dissolution in rocks, oxidation, compaction of organic sediments, pit development in karst lands, or human activities, Includes unseasonable harvesting of fluids from the ground such as oil and gas water. In recent years, in Iran, with the increase in the amount of subsidence due to buildings, runways, bridges, tunnels, streets, rail and road transport, agricultural facilities change the direction and direction of river movement. The canals and canals and fertility of agricultural lands have been damaged and also damages the flow pattern of hydrology, tilting and diversion of power towers and so on. Buildings that are larger and taller are more vulnerable, such as railways, earthen dams, canals, power towers and telecommunications.

The method of this study is analytical and field research. In this study, ground data consisting of 18 piezometers from 1382 to 1396 for the calculation of groundwater loss rates, groundwater levels in the minimum and maximum periods were prepared by interpolation of their interpolation maps. Exploration wells were used to calculate aquifer discharge levels and radar data including Sentinel 1 images were used to calculate subsidence rates from 2015 to 2018 and finally between the groundwater and subsidence factors in the correlation area. It was obtained from field survey data of their validation

In this research, differential radar interferometry has been used to determine the extent and extent of subsidence in Noorabad plain. In order to produce spatial pattern maps of the extent and amplitude of the meeting, a pair of radar sensors were used at different time intervals to perform interferometry. Due to the variability of the amount and amplitude of the meeting, caused by water harvesting as a positive factor as well as the role of natural endowments (precipitation) as a moderating factor, images were processed over time periods consistent with the crop calendar and rainy seasons. . The findings confirm the occurrence of a maximum annual subsidence of 3 cm in an area of 186 square kilometers. The occurrence of such phenomena is largely contemplated due to agricultural structures in other parts of Iran, because in Iran, due to the existence of a special agricultural calendar for irrigation in spring and summer, as well as the possibility of recharge in winter and early spring, The relative importance of the table and its impact on meeting rates for later periods is accepted and relatively inclusive. With the output of radar imagery output over 4 years, the results show that from 2015 to 2018, the aquifer level will increase substantially, with areas in the central and eastern parts of the aquifer having the highest aquifer rate in the regions. The residential and agricultural area has been developed in such a way that the effects of these meetings are evident in the residential and agricultural land and the blue areas show signs of uplift when descending to a subsidence area. It does not occur, but rather a double or elevated aquifer surface. In the analysis section, we study the status of the subsidence rate in the study area using radar images during the years mentioned, by examining the status of the piezometers and the rate of subsidence during these years showed that the situation of the subsidence area which is very high in 2015 is 8 km Which is 34 km in comparison to 2014 and in 2016 is 40 and 86 in 2017 and 2018 respectively. Based on the maps we see in these 4 consecutive years that we see the sum of each year The level of the plain has been increased and thus the summit on the plain has become a danger.

The average subsidence rate is about4 cm per year. The average subsidence over the four years is about 36 square kilometers of aquifer area, which covers about 5% of the area, with wells concentrated and the highest groundwater abstraction and concentration of existing cities and villages. In these areas, due to the water supply of the residential community including Nourabad and the surrounding areas, as well as the supply of water to the industrial sector, including factories and agricultural activities, the availability of more water resources and the availability of groundwater is very high. The high drop has been attributed to the high potential of these areas in the subsidence debate with the involvement of arid climates in the area, and has been identified as one of the critical areas of the city in the subsidence map. Radar interferometry results show that excessive withdrawal from the surface of the underground reservoirs has caused the downstream portion of the aquifer to collapse, as well as the presence of numerous aquifers at the aquifer level causing damage to residential sites. One of the areas most exposed to flooding in the plain is the groundwater loss in the eastern, central and southern part of the aquifer within about 14 m of about 14 m in the same well and the results of R2 coefficient correlation of 72% The significance level of 99% was obtained indicating that there is a direct relationship between these two parameters.