Explanation of the Geomorphologic Process and Effect of Subsidence on Land ‎Pattern Change in Geomorphologic Forms Case Study of Yazd-Ardakan Plain

Introduction :

Earth subsidence is one of the natural hazards under several conditions, including over-‎exploitation of groundwater, large dams, mining, extraction of fluids from the earth, ‎tectonic and so on. The subsidence causes changes in the geomorphic phenomena of arid ‎and semi-arid regions, which are important due to the occurrence of human complications ‎on different forms, the study of changes due to subsidence in these phenomena is ‎important. Due to the fact that the rate of change in land subsidence as well as the speed of ‎the geomorphological phenomenon is very slow and slow, measuring instruments are of ‎great importance. In this case, static technique is not suitable for monitoring, and dynamic ‎techniques should be used. One technique is the production of radar data. Today, radar ‎interferometry is a common method for measuring the surface deformation of the earth's ‎crust. Global coverage, good resolution of radar images, acceptable accuracy, repeatability, ‎the ability to monitor all areas of study at different time periods, this technique is a ‎powerful technique for studying and measuring land surface changes.‎ Case study:‎ The studied area is Yazd-Ardakan plain which is located in Yazd province. The area of ‎Yazd-Ardakan plain is 11775 square kilometer cover withe longitude are 53º15̍ to54º50̍ ‎east and latitude are 31̊15̍ to31̊15̍ north. ‎

‎ Data and method:

‎ Data used in this study‏ ‏are divided into two general categories, include Scrolling‏ ‏data ( field ‎data for three pilot) and earth observation satellites are data collected from four satellite ‎such as ENVISAT ASAR and Sentinel l satellites from the European Space Agency, ‎Digital Elevation Model ALOS PALSAR Sensor from the University of Alaska, Landsat ‎Satellite from the USGS, survey data from NCC ‎ of Iran as well as data from the studied ‎area. And GIS data including Stream, land use, watershed data related to Yazd plain of ‎Ardakan from the NCC of Iran.‎ This research is based two main steps. The first step is to calculate the amount of land ‎subsidence, for which the images of Sentinel 1 and ENVISAT ASAR satellites were ‎extracted from 2003 to 2018, and using the interferometric method, the amount of ‎subsidence of Yazd plain of Ardakan was calculated and in the second stapes, the ‎geomorphological condition of Yazd plain of Ardakan was studied. To detect changes in ‎geomorphic phenomena digital using with Elevation model ALOS PALSAR Satellite and ‎Landsat satellite imagery‏ ‏that extracted drainage from a digital elevation model using digital ‎stream extraction method. Landsat satellite imagery after preprocessing using edge ‎detection filtering to detect changes in phenomena in specific times series. and last stepe, ‎the relationship between the rate of land subsidence and the changes in geomorphological ‎phenomena was identified.‎ Stream Extraction from a digital elevation model:‎ A digital elevation model with a special resolution of 12.5 meters is derived from ALOS ‎PALSAR data for drainage pattern extraction. The extraction of drainage pattern from the ‎aforementioned digitization model was carried out using the Hydrology tool in the ArcGIS ‎software package and based on the value thresholds of different accumulation rates.‎ Select the Landforms of the study area (Three indicators landform)‎‏ ‏ Initially, the whole range of Yazd plain of Ardakan was considered and then the water ‎density map for Yazd Plain of Ardakan was produced. In addition, the map of land ‎subsidence was extracted for the study area, and then two maps were automatic ‎superimpose. The highest density of the streams, which corresponded to the subsidence, ‎selected as a pilot. Drainage pattern more over change due specific morphological can be ‎to generate version which local SHAGH (the crack which can font exist in area of ‎subsidence from) drainage pattern furthermore the stream pattern has been change in ‎special form and density level it is important to mention that extraction specific this ‎increases surface erosion‏.‏Then Galli's pilot is similar to the previous two‏ ‏pilot‏ ‏automatic ‎superimpose‏ ‏on subsidence map. Largest Galli that was on a descending region was as a ‎pilot‏ ‏selected.‎ Differential radar interference technique:‎ This term is used to measure parameters such as topography, surface-displacement and ‎surface displacement due to phase interference of two or more radar images with virtual ‎holes derived from the same region. This method is able to detect surface changes ‎occurring on the ground at different intervals with millimeter precision using at least three ‎‎(two + DEM + or more radar images).‎ The interferometer includes the phase difference between two images. The height at each ‎point of the region is determined at the time interval between the two images by the phase ‎difference check. The interferometer is created by the mixed blend of the original image in ‎conjunction of the dependent image. After interferometry method, ENVISAT ASAR and 1 ‎SENTINEL images created the interferometric and, after the final processing, converted to ‎vertical displacement values in meters per meter.‎ In two times, we had a subsidence of 13 centimeters in the study area, which has occurred ‎in Ardakan, Meybod, Rostaq and Takhzar areas. The highest abandonment rate is in the ‎Ibrahimabad area.‎

‎ The phenomenon of subsidence causes surface morphological changes such as changes in ‎the pattern of surface currents. On the data processing field study and integration of this ‎data need out that tree phenomena were surface to maximum changing namely SHAGH, ‎GALI and stream pattern .in additionally the reach was shown the change shagh length ‎from 2003 to 2018 rate of increasing 202% from 18 km to 56 km, and the Galli' area ‎increased by 50% from 4 hectares to 6 hectares and the streams increased by 47% from ‎‎165 hectares to 241 hectares.‎