Document Type : Applied Article
Professor of Geomorphology, Faculty of Social Sciences, Mohaghegh Ardabili University, Ardabil, Iran
PhD Student in Professor of Geomorphology, Faculty of Social Sciences, Mohaghegh Ardabili University, Ardabil, Iran
PhD Candidate in Rural Planning, Farhangian University of Tabriz, Tabriz, Iran
Landslide is a term that includes all types of slope movements and causes mass movement of materials on slopes. This term includes all processes that lead to mass movement of materials on slopes and according to the type of movement, it can be classified as sliding, flow, or falling movements. and creep is classified. The instability of natural slopes is one of the geomorphological and geological phenomena that plays an effective role in changing the shape of the earth's surface. Recognizing areas with landslide potential and zoning them is one of the basic steps in managing environmental hazards and reducing damages caused by this phenomenon, because this phenomenon causes financial and human costs, soil and land destruction, and increased sediment production in the basin outlet. Iran, with its mainly mountainous topography, high tectonic and seismic activity, diverse geological and climatic conditions, has the main natural conditions to create a wide range of landslides. Landslides in Iran, as a natural hazard, cause a lot of human and financial losses to the country every year.
Materials and methods
Radar satellite images: In this research, Sentinel 1 images, which captures images in the C-band range of microwaves, have been used. Then the necessary processing was done through SARSCAPE 5.2 plugin in ENVI 5.3 software and the technique used in this research to determine the amount of subsidence is the differential interferometric method with combined opening of two frequent or non-frequent passes. One of the most basic steps in radar interferometric processing is the selection of the appropriate image pair, which several factors such as sensor frequency, spatial baseline, time baseline, and spatial overlap along the sensor movement are effective in selecting the image pair. In this research, two SLC type Sentinel-1-A images from 2015 and 2020 were used.
Discussion and Results
By studying how and the possibility of displacement on the surface of the earth, it is possible to estimate the influencing parameters in the process of displacement of the earth, and it can be used in geophysical modeling and determining the necessary solutions to deal with range movements. Among all ground and space methods for measuring changes in the earth's surface, the radar interferometric technique is known as a useful tool and the best method. The amount of displacement shows the domain movements in the studied area. Positive values indicate the amount of displacement in the direction of satellite sensors and negative values indicate the amount of displacement against the direction of the sensor. The amount of movement of slope materials measured in the study area shows a maximum of 23 cm and a minimum of 18 cm in the study area in the years 2015 to 2020, the highest amount of slope movement is in the south of Hashtroud and the lowest is in the north of Hashtroud.
The radar interferometric method is a very accurate method that can detect domain movements using two images of the same area in different time intervals very accurately in centimeters and even millimeters. The results of field research also confirm the high accuracy of satellite images. By using this technology, it is possible to monitor small movements of the earth's surface continuously, with high accuracy and in a wide area. Radar images have identified domain movements in the studied area with very high accuracy. The results of this research showed that radar images have a good potential for revealing the instability of domains and calculating their displacement. The maximum amount of material movement is 23 cm in the studied area. The process of doing the work is based on a combination of library and field methods and using satellite images. For this purpose, first, a map of landslides in the region was prepared with field visits. Then, by reviewing and examining the sources, the factors that can be effective in the process of landslide occurrence, extracting and examining the sources, natural and human factors such as soil, slope, distance from the waterway, distance from the road, geology (lithology), precipitation, height to prepare a map Landslide risk zoning and potential were used. The resulting map was classified into 5 risk classes and evaluated according to the landslides that occurred in the studied area. According to the results of the evaluation, the used models show a suitable ability to predict the occurrence of landslides. The analysis of the results showed that the amount of precipitation and altitude play a greater role in creating high-risk areas than other factors.