نوع مقاله : مقاله پژوهشی
1 دانشجوی دکتری ژئومورفولوژی، دانشگاه حکیم سبزواری.
2 استادیار ژئومورفولوژی، دانشگاه حکیم سبزواری.
3 استاد ژئومورفولوژی، دانشگاه حکیم سبزواری.
4 استادیار سنجش از دور و GIS، دانشگاه حکیم سبزواری.
عنوان مقاله [English]
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.