جستجوی مقالات مرتبط با کلیدواژه "subsidence" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

In recent years, problems caused by human interference in the Salmas Plain, such as an increase in the irrational use of surface water resources, an increase in the process of groundwater discharge, and a change in land use have caused pressure on the groundwater resources of the region; hence, land subsidence is at least a natural response to the decrease in groundwater level. Therefore, it is important to study and identify subsidence areas in the region.

In this research, groundwater information and Sentinel 1 radar images were used. Groundwater information was obtained from the regional water company of West Azarbaijan province. In the present research, the DInSAR algorithm was used to measure the ground surface displacement, and the phase difference of the SAR signals was determined using the repeated-pass interference methods. Finally, by using the manual of differential radar interferometry with synthetic aperture and 52 even numbers of Sentinel 1 image, the subsidence in the Salmas Plain was determined between 2014 and 2015 and 2018 and 2019. Validation of the radar interferometry method using Qareqeshlaq Geodynamic station data, as well as groundwater level changes, underground water drop and field observations was conducted.

The results of the subsidence study using the DInSAR method showed that the average annual displacement rate is about 5 cm. Investigation of groundwater changes also indicated a decreasing trend in most of the wells. The wells located in the eastern and southeastern regions (e.g., Kangarlu, Qareqeshlaq, Yushanlu, etc.) have the highest amount of groundwater drop. In the study period (2014 to 2019), where the wells with an increase in groundwater level were affected by their proximity to the Zola dam reservoir and the water supply channels. The wells of Qezeljeh, East Qareqeshlaq, and Maidan Doab have the highest water level reductions, but they do not have sufficient water supply from the dam. Mahlam, West Tazeshahr, and Ian wells, which are in the western part of the plain and close to the dam lake, respectively, have a suitable increase. Checking the subsidence maps of the Salmas plain showed that most of the subsidence is concentrated in the southern areas, especially in the southeast of the plain, in comparison to other parts of the plain the depth of alluvium is also greater in these areas. This subsidence trend continued from 2014 to 2019 and this trend is also prevalent in the final map. During this period, the average water level changes in the Salmas plain aquifer had a downward trend, which was in harmony with land subsidence. By reviewing the groundwater drop map, it was found that the areas with the highest drop coincided with the subsidence areas. More drop in underground water indicated more water extraction. Therefore, the discharge of underground water in the region has caused subsidence.

Before adopting any operational plan and policy for implementation, it is the most important task to identify the exact location of land subsidence in any area, in particular residential areas. Sentinel1 radar images are sufficiently capable of solving this problem at all stages; however, a longer observation time would be more useful for decision making and implementation. Land subsidence in the Salmas plain is fully confirmed by the change of the underground water level and field visits. According to the DInSAR approach, the average displacement rate due to subsidence in the region was 5 cm, which can be fully verified in terms of observations of changes in the groundwater level. The piezometric data show a reduction of in the water level in most wells compared to the past, which depicts the occurrence of excessive extraction of groundwater. In addition, field surveys have been conducted in different areas of the Salmas Plain and the subsidence areas have been recorded. The process of subsidence in the studied area is ongoing, and the attention and care of the relevant authorities is needed to reduce the damage caused by this phenomenon and adjust the possible damages. It is recommended that people should be aware of the consequences of excessive harvesting and recommend alternative crops with a low annual demand for water and early yields.

The aim of this study was to model the subsidence of Abarkouh plain using inSAR and artificial intelligence techniques. At first, the subsidence map was prepared using the 46 Sentinel - 1 radar images (2014 – 2018) and radar interferometry techniques. Then, the Feedforward artificial neural network (ANN) algorithm was used to model the subsidence. In this algorithm, groundwater level changes (2014-2018), groundwater level, aquifer thickness, clay thickness in the aquifer and the clay thickness in the range of groundwater level changes (2014 - 2018) were introduced as input layers and the subsidence layer obtained from the radar interferometry method was introduced as an output layer to model training. These five parameters were obtained from the measured data set of 34 piezometer wells and 77 logs available in the archive of Regional Water Company of Yazd province. After initial checking of the data accuracy, the Kriging interpolation method was used to extend the five parameters to the whole region and the raster layers were prepared. The results of inSAR showed that maximum subsidence in parts of the studied area, i.e. in east, north - east and north, were 6, 2.7 and 1.6 cm/year respectively. Also, in order to verify the accuracy of the map resulting from using a neural network model, it was compared with the map with the radar imaging method. For this purpose, model evaluation criteria such as Nash-Sutcliffe (NS), RMSE,,MAE)and MARE were used, which 0.9524, 0.0018, 0.0012 and 0.1545 were obtained respectively.

Rapid population growth, increasing water demand, decrease in precipitation, and occurrence of drought may increase the use of water resources, especially the extraction of groundwater resources, leading to a drastic decline in groundwater level, and consequently the occurrence of land subsidence phenomenon. There are various methods for monitoring land subsidence. However, from among ground and space-based methods for the detection of earth crust deformations, the application of Interferometric Synthetic Aperture Radar (InSAR) on the collected data is considered as the most proper method in terms of accuracy and continuous spatial coverage. 

Located in central Iran in the west of Yazd Province, Abarkouh plain is a part of the Abarkouh – Sirjan basin, covering an area of 1390 km2. The area consists of alluvial fans and plains, surrounded by mountains on the west, south, and southwest and bounded on the east by Abarkouh Playa. This study used 46 satellite images taken from 2014 to 2018 to measure the amount of land subsidence in the Abarkooh plain. Moreover, the Shuttle Radar Topography Mission (SRTM) DEM was applied with 30 m resolution to remove the topography effect. A small Baseline Subset (SBAS) time series analysis was also performed to examine the short-term and long-term behavior of the subsidence.Decline in groundwater level and the subsurface sediment thickness are the two most important factors affecting the subsidence. The data used in this study were collected from 34 piezometric wells and 77 geologic logs. Finally, the most effective factors involved in subsidence and their relationship with other factors were investigated by comparing the output of the subsidence map and other existing maps.

The study's results indicated that the subsidence occurred in the east, northeast, and north of the area with the maximum accumulated value of 21, 10, and 6 cm, respectively, over four years. Moreover, the study of groundwater level and the thickness of fine-grained sediments showed that despite the decline in water level throughout the whole plain, subsidence is observed only in regions with clay subsurface sediments. According to different trends of decline in the groundwater level of the study area, groundwater level variations are changed during three periods. Accordingly, the water level declines during the first period in the east, northeast, and north of the area, while it increases in the west and southwest of the region. However, the decline in water level occurs throughout the whole region during the second period, and it is decreased at a lower rate in the east, north, and northeast during the third period.

In the first period, the comparison of the location of areas with increase or decrease in their water level with their corresponding areas on the Landsat showed that the water level declined in those residential and agricultural areas where there are more water wells, and, therefore, the subsidence rate is much more than other areas. On the other hand, the study of areas with an increase in water level suggested that the aquifer of these areas was recharged by mountains and alluvial fans.In the second period, those areas whose water had declined in the previous period experience more decline. Therefore, it can be concluded that the aquifer had not sufficiently been recharged in wet periods. In other words, the increase in the decline of the areas' water level occurred due to the decrease in the recharging of the underground waters because of several years of drought, and the increased groundwater withdrawal caused by the development of agricultural lands. However, despite the sharp decline in the areas' water level, no subsidence was found in the region.In the third period, some piezometric wells were dried, and the water level decline was significant in the west and southwest areas, which could be attributed to factors such as increased acreage, creation of new industrial centers, etc. Therefore, it could be argued that the subsidence rate of this four-year period will certainly return to the hydraulic conditions before this period. Thus, it can be concluded that in addition to the decline in groundwater level, other geological and hydrogeological factors play an important role in causing subsidence.

Recently, land subsidence due to natural and human factors changed to catastrophic destruction for the residential, agricultural and industrial areas. In this study, the high potential subsidence areas of Ardabil plain were identified to control and manage this phenomenon. Thus, the seven effective parameters on the subsidence were rated and weighted and the subsidence potential index (SPI) was calculated for study area. The SPI value for the Ardabil Plain was obtained between 80 and 154. Then the results of this method were verified by occurred subsidence which is obtained through INSAR image analysis for the study area. Although the results are acceptable but to increase the framework efficiency and accuracy of results, the fuzzy model adopted to optimize this framework. In this way, seven effective parameters on the SPI were used as the input of the FL model and the value of the corrected SPI by obtained observed subsidence from INSAR images was defined as the output of the model. The results of this method showed that the southern and southeastern parts of the plain have the high subsidence potential.

Land-subsidence phenomenon is one of the geomorphologic hazards known in arid and semi-arid areas in recent years. The main objective of the present study is to provide a land-subsidence spatial modeling and its assessment using the generalized additive model data mining technique in Jiroft Plain, Kerman Province. Land-subsidence inventory map was prepared for the study area using extensive field surveys. Evidential Belief Function was used to investigate relationships between land-subsidence and 10 effective factors including slope percentage, aspect, elevation, lithological units, distance from river, piezometric wells data, land use, plan curvature, topographic wetness index, and distance from fault, and the weight of each factor class was determined. Results of the relationships between land-subsidence and effective factors indicated that most of the subsidences of the region are occurred in low slopes (0-2%), flat and smooth aspects, small distance from a river (>50m), large distance from a fault (>4000 m), also in the third group lithological units (rhythetic dyke and rhyodity and dark green tuff), shrubbery land use type, convex slopes with high topographic wetness index (>12), and receding in groundwater level. A land-subsidence susceptibility zonation map was created using the GAM in statistical R statistical software for the study area. Results of validation of generalized additive model evaluation using 30% of unused points in the modeling process, and the receiver operating characteristic (ROC) showed that the land-subsidence susceptibility map prepared by Generalized Additive Model had a high accuracy (81.20%). Therefore, the map might be helpful for optimizing management of water resources and preventing the re-occurrence of this phenomenon in the area. Results of ranking effective factors from the generalized additive model showed that elevation, land use, and aspect were in the highest orders in land-subsidence occurrences

Differential synthetic aperture radar interferometry (D-InSAR) has become a useful technique for monitoring ground movement. The technique enables the analysis of very small ground movements in continuous and large areas and has the advantages of high accuracy, high resolution, all-weather adaptability, low cost and inaccessible area coverage. Thus, D-InSAR has been widely used for investigation of geologic hazards, such as subsidence, landslide, earthquake, and volcanic activity. In this research, D-InSAR technique was applied for detection of unstable slopes and determining moving displacement rate. For this purpose, eight SAR images of PALSAR sensor of ALOS satellite were selected for processing based on D-InSAR approach. Obtained results were validated by field observations prates. This paper is only represented results related to image pair processing of 5th July to 5th October 2007 with 92 days interval. Garm Chay watershed with 940 km2 area is located in North Eastern and 40 km far from Miyaneh in Eastern Azerbyjan, Iran. This region with 380 landslides is considered as one of the unstable landslide proven area in Eastern Azerbyjan. Occurrence of these slides caused heavy damages to rural properties and arable lands. As a result, Sovin village in north western part of this watershed was moved to other safesite. The results clearly showed that some old stabilized landslides were still active. Because of their proximity to local stream networks (check the possibility for stream displacement), they can be considered as important sources of sediment yield. Before mentioned period, the maximum displacement was calculated 5.8 cm in landslide surface near to Avin, Atajan and Benavaran villages. The results from this method should be validated by geodetic methods and field obsevations.