Geomorphology
sayyad Asghari Saraskanroud; Fariba Esfandyari; Mehdi Faal Naziri; Batool Zeinali
Abstract
Land subsidence refers to the gradual or sudden lowering of the earth's surface as a result of various factors such as tectonic activities, mining, oil and gas fields, and illegal extraction of underground water. In Alborz province, the growing trend of population and migration in recent years has ...
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Land subsidence refers to the gradual or sudden lowering of the earth's surface as a result of various factors such as tectonic activities, mining, oil and gas fields, and illegal extraction of underground water. In Alborz province, the growing trend of population and migration in recent years has added to the increase in demand and the amount of water withdrawal from the underground water table, so it is subject to subsidence due to the sharp drop in the level of underground water. In this research, subsidence assessment was done using radar interferometric technique, and then, prone areas were zoned with multi-criteria algorithm in the time frame of 2016 and 2023. The results of information extraction with interferometric technique showed that the average amount of subsidence in the urban boundaries of Saujblag, Karaj, Nazarabad, Chaharbagh and Fardis is between 15 and 320 mm. According to observations, the highest amount of subsidence is in the eastern part and then in the southern and southwestern parts. According to the estimated results of subsidence risk zoning; The parameters of water level drop, land use, slope and geology, respectively, with weight coefficients of 0.16127, 0.141875, 0.130145 and 0.128474, are the most important factors in creating the risk of subsidence in the study area, which are 31 and 23%, respectively. From the range, it has a very high and high probability of danger.
Robabeh Farzinkia; Mohmmadali Zanganehasadi; Abolghasem Amirahmadi; Rahman Zandi
Volume 6, Issue 20 , December 2019, , Pages 165-185
Abstract
1- IntroductionToday, the phenomenon of land subsidence is one of the most important geomorphologic hazards on a global scale, causing a great deal of damage to urban and rural construction. According to the UNESCO definition, "subsidence is the collapse or land leveling that occurs due to different ...
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1- IntroductionToday, the phenomenon of land subsidence is one of the most important geomorphologic hazards on a global scale, causing a great deal of damage to urban and rural construction. According to the UNESCO definition, "subsidence is the collapse or land leveling that occurs due to different large and small scale causes" (Amir Ahmadi et al., 2013: 2). Pourkhosravani et al, (2012) Only with radar interferometer technique studied the geometry of duality, The results of this study showed that, firstly, citing excessive productivity of underground waters is not the main reason for the subsidence phenomenon; secondly, the phenomenon of subsidence in Iran's plains is the result of a duality in the crustal motions between the plains and adjacent mountains. In this research, the tectonic indexes and radar interferometry technique have been used with regard to the data and information available to detect the tectonic activity of the area.2-MethodologyIn order to investigate the state of activity of the newly tectonic area, topographic maps of 1: 50000 and 1: 10000 map of geology and radar images are used in the earthquake discussion from USGS US from 1923 to 2018. Also, to study the subsidence of the Joveyn area, the satellite Sentinel-1A satellite radar data for 2017 and 2018 was used in Canada and processed by SNAP software. The resources used in this research were based on library studies and surveys, topographic maps and radar images and field surveys.3-Discussion and results and findingsThe results of the used Indicators, earthquake zoning and radar interference are defined in the research as follows:River Gradient Index) SL): This index was first presented by Hack (1973), in the study of the role of rock resistance on water flow in the Appalachian Mountains in the southeast of America as numerical values of the river gradient index Table1).Table(1): River Gradient Index)SL)HighΔH(m)ΔL(m)Lsc(m)SlCondition1200-13001001476932050217low1100-12001001581467170424medium1000-110010029798122931412medium-Asymmetric index(AF):In this calculation, the obtained numbers (33.7) of the basin showed that the value of the index is less than 50. Therefore, we have the tectonic activity on the left side of the main stream and we face the subsidence phenomenon on the right.-Reverse topographic symmetry index: (T)to calculate this index in the Joveyn basin, a section has been created in each sub-area and its value has been calculated. According to (table 2), the index value in all three sub-basins is less than 1, indicating the asymmetry and active tectonics in the whole basin. Table (2): Reverse topographic symmetry indexRouteDa(km)Dd(km)TCondition118/4321/330/86active215/3816/910/9active314/5316/780/86active-Hypsometric and Hypsometric Integral CurvesIn the hypsometry integral, the numerical value has a value of 0.5 in the range of young to adult topography.Mountain Sinocity Index: (Smf)Table (3): Mountain Sinocity Index shapeLMFLSSCondition126/9412/342/18Semi active241/8611/853/5Semi active333/0518/721/76active446/0223/041/99active-Sinocity index of the river: (S)According to the calculations, the index of the main bend and bend of the main river is less than 1. Which represents the new activities in the region.-Valley Depth Wide Index (VF):In passive regions, the average value of this indicator is usually higher than 7 in terms of over-rupture (Ranjbar Manesh, 2013).Table(4): Valley Depth Wide IndexConditionVfVfwEldErdEscnumberactive1.3629205721101604Figure 1active0.8127140814981307Figure 2active0.873135414241301Figure 3active1.6220153416841475Figure 4active2148150514811421Figure 5active1.2127154515271437Figure 6active0/287232421151877Figure 7-Radar interferometric resultsAccording to this map, the maximum subsidence rate in the study area in 2017 and 2018 will be 6.4 and 5.6 respectively. Regarding the maps drawn on this plain with radar interferometry, both indicate the subsidence of the plain. The analysis of plain radar data shows that the highest elevation in the joghatay heights, and the highest subsidence level, occurred on the joveyn Plain floor.4-ConclusionAlthough most scholars consider untreated groundwater to be an important factor in groundwater depletion and the plains of Iran, the role of tectonic factors in exacerbating this phenomenon should not be overlooked. In a study conducted by Purkhosrovani et al. On the causes of the subsidence, only Duval's discussion of radar interferometry was discussed without examining tectonic indices. In this study, in addition to radar interferometry, the tectonic status of the basin was also investigated. For this purpose, geomorphic indices such as watershed shape, drainage basin asymmetry index, inverse topographic symmetry index, mountain front sinusoidal index, hipsometry integral, valley floor height to its height, river sine index, river gradient index, gradient index They offer some of the activities of the area's baby boomers. Among the morphotectonic indices that all indicate tectonic activity in the region, the VF index in the region was less than 2, which by standards is below 6 in this index indicating rising areas. Subsidence caused by tectonic movements occurs when there are two faults, graben and upwelling, and relative movement of parts causes subsidence. The fault status of the area in the southern and northern parts of the region has placed the plain in the graben position. Statistical analysis also showed that the earthquake of 1923 occurred with a magnitude of 6.4 MS. The future activity of these faults may affect the area. The active morphotectonic conditions of the basin, also showed the results of radar interferometry, in the southern part with higher elevation, parallel to subsidence in the plain. The existence of this scouring and its appearance on the radar interferometer map indicates the tectonic activity in the southern rangesof the study area. These results indicate a significant relationship between the subsidence and its lateral elevations, suggesting that these two movements are dual. Based on the above arguments, it can be concluded that one of the factors affecting the subsidence of the Earth in the juvenile plain is due to its soft crustal motions even in equilibrium. Due to the geomorphic hazards of the basin, it is necessary to prepare a zoning map of the area for development activities and land preparation based on which control, protection, prevention or warning measures will be taken.
Siavash Shayan; Mojtaba Yamani; Manizheh Yadegari
Volume 3, Issue 9 , March 2017, , Pages 139-158
Abstract
Geomorphological features are the basis of natural resources evaluation in the watersheds. These features are affected by many factors such as climate and soil, hydrology, ecology, geology etc. Drainage network in this area was different according to the amount and performance of processes and has different ...
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Geomorphological features are the basis of natural resources evaluation in the watersheds. These features are affected by many factors such as climate and soil, hydrology, ecology, geology etc. Drainage network in this area was different according to the amount and performance of processes and has different effects on their surroundings. Sinkholes are located on the way of this drainage network. In association with the occurrence, the researchers have counting on this subject that the change of soil parameters, indiscriminate harvesting from groundwater, drilling of illegal wells and activity of Shahid-Mofateh thermal power plant are the most important factors for the appearance of these profound sinkholes in the plains of this state. The aim of this study is examining the characteristics of the drainage networks in this region, and study their role in the creating of subsidence in this region. For this purpose all information on geology, hydrology, hydrogeological and geographical data in this area were collected and analyzed. Drainage networks, lithology, slope and elevation of this region were drawn by using of digital topographic maps of 1:50000, geological of 1:100000, DEM and also pictures of Google Earth. Then to evaluate annual changes of runoff we used experimental method of Justin and Katain. The results indicate that the dissimilar changes in morphometric data of drainage network in this area due to the climatic and geological conditions, were most important factors in the intensification of decrease of soil humidity, subterranean water and occurrence of subsidence in this region. Human factors and the over use of water sources were effective in the intensification of subsidence.
