Geomorphological Hazards and Settlement Instability: A Case Study of Razg Village in Birjand County

Introduction
When a natural process poses a threat to human life or property, it is called a natural hazard. Geomorphological hazards are among the environmental processes that cause serious disruption to human activities worldwide. Iran is located in a region characterized by the occurrence and recurrence of natural disasters and accidents. Iran is one of the most vulnerable countries in the world. Planning in these settlements requires accurate knowledge and analysis of the conditions and ultimately its prediction and planning. Natural disasters such as floods, earthquakes, landslides, collapses, etc. have threatened human settlements, including cities and villages, since the distant past. Many villages are exposed to natural hazards due to the geographical conditions in which they are located. The extreme vulnerability of villages to natural hazards is a characteristic of many rural areas of the country. Part of these problems are due to the inappropriate location of villages in river basins, near faults, and on unstable lands, etc. One way to reduce losses from natural disasters is to identify areas prone to disasters and prevent development in those areas using land use planning. In this regard, geomorphologists play many roles in hazard research. In recent years, the capabilities of geomorphologists to play these roles have increased. Therefore, in this study, the following questions were raised about the village of Rezag:Is the settlement of Rezag village appropriate? Given its location, what risks does Rezag village face? Given the importance of the issue and the fact that no research has been conducted in this regard in the study area, the purpose of this research is to investigate the geomorphological hazards of the settlement of Rezag village in Birjand city.
 
Methodology
In this study, a field visit was first made to Rezag village, and the settlement, hazards, and residential structures in this village were evaluated. Through GIS shape files using Arc Map and Google Earth Pro software, the geomorphological hazards of the settlement of Rezag village in Birjand city were examined and analyzed. Library resources and articles related to geomorphological hazards, Bagheran rural district, and Rezag village were collected and used in this study. In order to prepare the required maps, geological maps, topographic curves, slope, and direction were prepared through the shape file of Bagheran rural district in Arc Map software using shape files. On the produced rural map, a study emphasis was made on Rezag village. To analyze geomorphological hazards, elevation classification map, surface classification map, river map, fault map and geological map were produced and examined and analyzed in each section. According to the produced maps, the hazards of the rural district and village of Rezag were examined and scientifically analyzed.
 
Findings
The village of Rezag is located in Bagheran Rural District at an altitude of 1834 meters and 12 kilometers south of Birjand city (in the Bagheran mountain range). The mountains south of Birjand, in the middle of which Rezag village is located, are a melange ophiolite complex, the majority of which is formed by ultramafic units. This village is located on a slope where the faults in the area are mostly intersecting, and erosion and water flow at the fault sites have caused the rock in the area to be severely weathered. The landslide surface of the village is also the result of this severe erosion. Rezag village is located on the slope of the mountain and between two valleys, the valley located in the eastern part of Rezag village is wider, which has caused the main road to access the village. The fact that the passage and the stream are the same in the village context and the lack of a canal design appropriate to floods with different return periods in order to guide the flood is considered the most important vulnerability of the village. The valley located in the northern part has more and greener soil cover and landslides that block parts of the river path. In the event of heavy rainfall, there is a possibility of landslides and floods in this part of the village. Therefore, construction should not be carried out on the landslide surface. It is necessary to create a path for the flood to pass through the landslide mass. In the village of Rezag, a fault with a southeast to northwest direction has crossed the eastern parts of this village. It is necessary for the respected village head to supervise the permits and construction of constructions that take place in the village. The faults within the village are similar to the faults in the region, which have caused numerous blocks to form within the village. The residential area of the village is also on the slope of one of the blocks resulting from the faults. The blocks resulting from the intersection of the faults have increased the risk of landslides in the village of Razag. Rezag village is located on a slope classification of over 30 degrees, which is not suitable for settlement in terms of slope. Rezag village has a gentler slope to the north, and a valley crosses the east of this village, which is the main road and access to this village and the higher villages in Bagheran rural district. The fact that the passage and the path are the same and the lack of a channel designed to be appropriate for the flood to direct the flood are the most important vulnerabilities of Rezag village.
 
Discuccion and Conclusion
In this study, the geomorphological hazards of the settlement of Rezag village in Bagheran rural district of Birjand city were investigated. The findings of the study and the produced maps show that Rezag village is located in an unsuitable location with a slope of over 30 degrees in terms of settlement. The fault that crossed Rezag village has an intersection where the fault location; erosion and water flow have caused the formation of a channel and caused landslides. The rock units of the region, including split basalts, play a major role in the landslide of Rezag village. In the northern and northeastern parts of Razag village, there is a landslide valley that has blocked the sliding surface of the river bed; in the event of heavy rainfall, it will cause flooding and landslides and the access road to the village will be blocked. It is recommended that the river path be dredged from the sliding surface. Due to the fault crossing and proximity to faults in the area, 100% of the village buildings will be destroyed in the event of an earthquake. It is recommended that before natural disasters occur, planning and implementation be made to secure the structures of Razag village. In terms of altitude classification, Rezag village is located at an altitude of between 1800-2000 meters. From a scientific point of view, in assessing the slope and direction; Rezag village does not have tourist potential and the village buildings are destructible and the structures are built on unstable slopes. It is recommended that in future research, the level of resistance of the structures of the villages of Bagheran rural district to natural disasters be studied and safe points for settlements be selected.