Showing 2 results for Sbas
Dr Amir Saffari, Dr Ali Ahmadabadi, Mr Amieali Abbaszadeh,
Volume 8, Issue 4 (1-2021)
Abstract
Subsidence is one of the most important natural hazards that has affected many plains of the country in recent years. Eyvanakey plain in Semnan province is among the plains that have faced this danger. Due to the importance of the subject, in this research, the evaluation of the subsidence risk and the estimation of the subsidence rate in this plain have been done. In this research, Sentinel 1 radar images, Landsat satellite images and SRTM 30 meters high digital layer are used as the most important research data. The most important research tools are GMT, ArcGIS and Super Decisions. Also, Fuzzy-ANP logic and SBAS time series models have been used in this research. This research has been done in two stages, in the first stage, the assessment of the subsidence risk and in the second stage, the estimation of the rate of subsidence in Eyvanakey Plain. Based on the results, 251 square kilometers of the study area (equivalent to 58.5% of the area) has a high and very high risk of subsidence, which mainly corresponds to the southern areas of the Eyvanakey Plain. Also, the results of the SBAS time series method have shown that the Eyvanakey plain has subsided between 28 and 533 mm during a period of 6 years. Considering that, the high risk class has the highest amount of subsidence in the study area, so it can be said that there is a strong relationship between the subsidence risk classes with radar images and the accuracy of the results of the subsidence risk classes is confirmed.
Dr Mehdi Safari Namivandi, Mr Alimohammad Gholami, Dr Parastoo Ghaforpuranbaran, Mr Kamyar Emami,
Volume 8, Issue 4 (1-2021)
Abstract
Objective: Land subsidence is one of the hazards that affect many plains in Iran, including the plains of Semnan province. Given that the risk of subsidence is associated with many harmful effects, this study evaluates the subsidence situation in the urban area and urban outskirts of Garmsar and analyzes the factors affecting its occurrence.
Methods: In this research, Sentinel 1 radar images, Landsat satellite images and information related to groundwater resources of the region have been used as the most important research data. The most important research tools have been ArcGIS, GMT and Google Earth Engine software. In this research, first, using the SBAS time series method, a map of the subsidence rate of the region has been prepared and then its relationship with the decline of groundwater resources and the type of land uses of the region has been investigated.
Results: Based on the results obtained, the study area has subsided between 12 and 79 mm during a one-year period (from January 2021 to January 2022), with the highest rate of subsidence in the southern outskirts of Garmsar city.
Conclusions: The results of this study also showed that the annual decline in groundwater resources in the southern wells of the region was more than 2 meters, and given that the highest rate of subsidence was also related to these areas, it can be said that the main reason for the subsidence of the region was the decline in groundwater resources. Also, based on the results, the development of human constructions, especially heavy structures, has been effective in intensifying the subsidence that has occurred.
