Introduction

The present study aims to assess slope instabilities in the Shahrchai Basin of Urmia using the logistic regression model. Slope instabilities are significant natural hazards in mountainous areas, having substantial impacts on human lives and infrastructure. These instabilities can be caused by various factors such as geological conditions, topographic features, climatic changes, and human activities. Specifically, the Shahrchai Basin of Urmia, due to its geographical location and unique characteristics, is prone to slope instabilities. Accurate assessment of these instabilities and identification of high-risk areas are of particular importance for planners and crisis managers. In this study, factors such as elevation, slope, slope aspect, distance from fault lines, distance from rivers, distance from roads, lithology, vegetation cover, and land cover were examined as variables influencing the occurrence of instabilities. The significance of this research lies in its potential to contribute to better identification and management of natural hazards and to reduce the damages caused by them. Additionally, this research can serve as a model for other similar areas and be adapted to the specific conditions of each region.



Methodology

In the methodology section, after conducting preliminary studies and collecting necessary data from various sources, maps of instability points distribution were prepared using satellite images. Online data included Sentinel-2 and Landsat-9 (2023) satellite images and a Digital Elevation Model (DEM) with a 10x10 meter pixel resolution. Geological and topographic maps were also obtained from institutional sources. Using GIS tools and data analysis software, maps of slope, slope aspect, distance from faults, rivers, and roads, as well as maps of vegetation cover and land cover, were created. Then, the logistic regression model was applied to these data, and the results were analyzed. For data analysis and preparation of sensitivity maps, various tools in ArcGIS and IDRISI software were used. Slope and slope aspect maps were extracted from the DEM, and maps of distance from faults, rivers, and roads were created using the Euclidean Distance tool in GIS software. Moreover, vegetation cover maps were prepared using the NDVI index and satellite data. Finally, by inputting all data into the logistic regression model, the final analysis was conducted, and results were obtained.



Findings and Discussion

The results of the logistic regression model indicated that variables such as distance from roads, slope aspect, distance from faults, and vegetation cover have a positive and direct relationship with instabilities and were identified as the most significant influencing factors. The logistic regression equation based on the obtained coefficients showed a significant relationship between independent and dependent variables. The sensitivity zoning maps of the area demonstrated that areas with very high risk occupied the smallest percentage of the total area. The analysis of the coefficients obtained from the logistic regression model showed that reducing the distance from roads and faults, increasing the southward slope aspect, and decreasing vegetation cover significantly increase the risk of instabilities.

For preparing sensitivity maps, various classes of slope, slope aspect, elevation, and other factors were precisely analyzed. The results showed that instabilities occur more frequently in areas with slopes of 5 to 20 percent and in south and southeast directions. Additionally, instabilities were more observed within 0 to 1000 meters from faults and in areas with poor vegetation cover.



Conclusion

This research aims to assess the potential risk of slope instabilities in the Shaharchay watershed of Urmia using a logistic regression model. The results indicate that the logistic regression model is highly accurate in identifying the factors influencing slope instabilities and in producing susceptibility maps for the area.

The analysis of the relationship between various factors and the occurrence of instabilities shows that distance from roads, slope direction, distance from faults, and vegetation cover are the most significant factors contributing to increased likelihood of instabilities. The probability of ground instabilities near roads is elevated due to human activities, soil weakening, and construction operations. Slope direction plays a crucial role in land stability by affecting factors such as water saturation, soil erosion, and solar radiation intensity. Proximity to faults increases the risk of instabilities due to tectonic activities and geological changes. Furthermore, vegetation cover acts as a stabilizing factor, playing a vital role in reducing erosion and preventing landslides; its absence can significantly increase the risk of instability.

Statistical indices used in this study, such as ROC, Pseudo R Square, and Chi Square, confirm the validity and accuracy of the proposed model. The high Chi Square value and appropriate Pseudo R Square value indicate a good fit and high predictive power of the model. Additionally, the high ROC value (0.9223) demonstrates a strong correlation between the independent and dependent variables in the model.

The produced zonation maps indicate the distribution of areas with varying sensitivities to slope instabilities. These maps accurately identify high-risk areas and can greatly assist planners and crisis managers in making effective decisions to mitigate risks and improve natural resource management.

The findings of this research can serve as an effective tool for crisis management and reducing damages caused by slope instabilities in the Shaharchay watershed of Urmia. It is recommended that planners and local managers utilize these findings to develop and implement preventive policies and programs. Moreover, this study demonstrates that logistic regression can be an efficient tool for analyzing and predicting slope instabilities in similar areas.