Introduction
Every year, landslides cause extensive human and financial losses, including the destruction of forests, fertile agricultural lands, residential areas, and communication networks. Considering that landslides are more manageable than other natural disasters; therefore, it is very important to know this phenomenon in order to prevent damages caused by it. Therefore, the present research was carried out in order to assess the risk of landslides and prepare a map of the severity of landslide damage in Bar watershed in Razavi Khorasan province. Landslide susceptibility assessment can help planners in the final management of environmental pollution and natural resources in preventing possible damages and ultimately developing economic activities in the watershed. The Bar watershed in the northwest of Neishabur city has the potential of landslides due to geological conditions, climate and human activities. Therefore, the need to identify areas prone to landslides, vulnerability and risk of landslides in this area can have positive effects on the life and economy of the people of the region. In this research, it will be tried to simultaneously study the risk, elements at risk, the vulnerability of elements due to the occurrence of landslides and finally the damage (risk) of landslides in the Bar watershed. As a result, the purpose of this research is to assess the risk of landslides and landslide damage using the severity of the risk, the elements at risk and the degree of vulnerability of the elements at risk, it is for the purpose of risk and damage management in the watershed area.
Materials and Methods
Bar Neyshabur watershed is one of the sub-watersheds of the Bar River watershed, which is located in the north of Neyshabor city. In terms of geographical location, Bar watershed is located in the range of 58°23'35° to 58°4'52°E and 36°28°9' to 36°7'N latitude and is located in the southern slopes of Binalud. In order to carry out this study, first, through library studies and field visits, the factors affecting the occurrence of landslides were identified and collected. The distribution map of landslides in the region was prepared with the help of the data provided by the General Directorate of Natural Resources and Watershed Management of Razavi Khorasan Province and modified using Google Earth satellite images and field visits. Then, 14 key and effective parameters on the occurrence of landslides in the region were selected. Next, the landslide risk map was prepared using the maximum entropy (ME) machine learning method, and then, the accuracy of the model was evaluated using the ROC index. In order to model the risk of landslides, 70% of landslide points were used to train the model and 30% of landslide data were used to validate the model. Next, the information layer of the elements at risk and the degree of vulnerability of the elements were extracted. Finally, the landslide damage map was prepared by combining maps of risk intensity, elements at risk and degree of vulnerability of elements based on the general equation of risk.
Results and discussions
Based on the results, the amount of surface area under the ROC index diagram in the validation stage was 0.854, which indicates the very good capability of the model in zoning and determining landslide prone areas in the Bar watershed. The results of the vulnerability map of the studied area showed that 56.9% of the Bar watershed were in the class of high and very high elements at risk. Meanwhile, 17.8% of this basin was placed in the high and very high class of landslide risk vulnerability. The reason is the absence of important facilities, large factories, highways, important structures and large recreational complexes in this basin. Also, the results of the risk zoning map of the studied area showed that 9.1% of the Neyshabur watershed, equivalent to 2503 hectares in the high and very high class, and 77.8% of the area, equivalent to 21450 hectares, were damaged in the low and very low class. The interpretation of the results showed that due to the presence of elements at risk in the region, most of the region has low and very low risk. This helps to focus the management work in the sectors that have a lot of damage and reduces the waste of time and money.
Conclusion
In this study, sensitivity, vulnerability, and risk of landslides were zoned in the Bar Neyshabur watershed in Razavi Khorasan province as a landslide-prone basin with an area of about 27,643.8 hectares. The natural conditions of the Bar Neyshabur watershed, such as geology, uneven conditions, geomorphology and tectonics, as well as human aggravating factors such as land use change and rural roads, have created a suitable platform for the occurrence of landslides, and a total of 73 cases were identified in the study area. In this research, it was tried to use all the effective factors in the landslide susceptibility assessment in the Neyshabur Bar watershed. According to the risk zoning map of the studied area, 9.1% of the Neyshabur watershed was damaged in the high and very high class and 77.8% of the area was in the low and very low class. The interpretation of the results of the number of landslides in each risk class showed that 41 landslides were found in the low and very low risk class. As a result, due to the presence of elements at risk in the region, most of the region has low risk and very low risk. The results of this study help to focus management work in the sectors that have a lot of damage and reduce the waste of time and money. |
