Analysis of Subsidence Status in Hamedan Urban Area using Radar and Satellite Images

The risk of subsidence in recent years has posed serious challenges to many cities, including cities in arid and semi-arid regions of Iran. Hamedan is one of the cities that are exposed to this risk and for this reason, this study evaluated the subsidence in the city. The data included Sentinel 1 radar images, Landsat satellite images, 30 m SRTM digital model and groundwater data. Tools also included ArcGIS, GMT, and ENVI. In the first stage, land use maps of the region for the period 1991-2020 were prepared and analyzed. In the second stage, the situation of groundwater depletion in the study area was explored, and in the third stage, using radar images and SBAS time series method, the amount of subsidence in the area over a three-year period (2017 to 2020) was calculated. The results showed that the urban area and suburbs of Hamedan annually experience one meter drop in water resources and 0.7 Square kilometers of physical development. Moreover, the subsidence rate of this area during the three-year period was between 6 to 98 mm. According to the final map, the rate in western areas of Hamadan was between 60 to 98 mm, in central areas was between 30 to 60 mm, and in a big part the city subsidence is 6 to 30 mm from its eastern regions. Considering that the highest rate of physical development of Hamedan city in recent years has been in the western suburbs of the city, it can be said that the physical development along with the decline of groundwater resources are the main factors of subsidence in this city.