Determining Geomorphological Restricted Areas in Bojnourd City in order to Locate Appropriate Directions of Urban Development from a Hazards Perspective

Introduction
Unplanned human activities in the environment lead to various risks and damages from human, social, environmental, and economic aspects that can have catastrophic effects and consequences with the help of planning and preparedness for emergency measures. The location of settlements and other man-made facilities is influenced by environmental factors, especially geomorphology and geology. A population explosion and the expansion of the dimensions and diversity of urban development patterns have accompanied accelerated urbanization and the move towards urbanization in the world. This increase in population in Iran over the past few decades has not been commensurate with the ability to equip urban spaces and expand infrastructure, and has created problems such as expensive housing prices, unemployment, and informal housing in the most severe way possible in the appearance of cities. The city of Bojnourd, as the administrative-political center of North Khorasan province, which has a special place in the residential system of the northeast of Iran, is the 44th city in Iran in terms of population. The rate of increase of urban settlements in Bojnourd plain has increased from 17% in 1998 to 37% in 2013, which has destroyed a large area of ​​agricultural uses and fertile gardens in the Bojnourd plain. Lack of suitable land for allocation to urban uses, economic poverty and inaccurate study and location of urban land uses, has caused the population in high-risk areas such as floodplains, rivers and canals privacy, settle near active faults and points with high water table. This issue has always been one of the concerns of city administrators and urban planners. In the field of locating cities using various natural and human parameters, many studies have been done on many cities inside and outside the country. Especially in recent years due to the importance of the issue, its understanding and the need for research such an upward trend has taken place. Considering that, so far no research has been done on determining the geomorphological restricted areas and locating suitable aspects of Bojnourd urban development from the perspective of risk. Therefore, it is necessary to conduct research on this issue in the urban and suburban areas of Bojnourd. The purpose of this study is to determine the geomorphological restricted areas in order to locate suitable aspects of urban development from the perspective of risk in urban and suburban areas of Bojnourd. In this study, with a systemic-environmental perspective, and with the idea that urban geomorphological studies are the basis for identification and management of the environment and risk reduction, by evaluating and locating appropriate spaces and directions of urban development in Bojnourd with geomorphological perspective and the influential components are dealt with systematically.
Research scope
The study area is the tectonic-alluvial plain of Bojnourd, on which the urban area of ​​Bojnourd and the surrounding towns are located.
 This plain is limited from the northeast to Garmkhan plain, from the north to Maneh plain, from the east to Shirvan Township, from the west to Badranlu river basin, and from the south to Esfarayen Township (Figure 1). In the present study, the urban area of ​​Bojnourd and Golestanshahr (Maskane Mehr) was surveyed up to a radius of 6 km based on experts. Physical growth towards high-risk areas, population settlement, establishment of equipment and facilities, and public and private investment in these areas, increased the risk of city limits from flood, earthquake, and water table hazards. These features have caused this city to have a fragmented and island growth. Geomorphological barriers have been the main limitations of development in the privacy of Bojnourd city.
 
Fig. 1. Location of Bojnourd city and its surrounding towns in
Materials and Methods
Regarding the systemic approach, environmental variables including geomorphological parameters, geology (lithology and active faults), topography (slope, slope direction and altitude), hydrology (distance from rivers and canals), and human parameters (Land use and distance from urban and demographic points) in the study area in the form of classification maps and layer fuzzy operation was performed. Using the ANP model, the final weight of each factor layer in the Super Decision software was obtained.  From the multiplication of the final weight obtained from the ANP model with fuzzy layers and using the Fuzzy Gamma 0.5 operator, an integrated map was obtained. The geomorphological restricted areas were identified from the perspective of urban development, the remaining areas of the study area into appropriate, and very inappropriately categories were classified.
Apply Prohibited Areas
In order to zoning and locating areas prone to urban development, after preparing the information layers, fuzzy layers were attempted and the prohibited areas were identified. Considering the purpose of the present study, which is to determine the prohibited areas and apply these areas in the location of urban development, by giving zero score to the prohibited classes, fuzzy construction was performed.
Results
The results showed that 57.7 KM2 equivalent to 21.24% of the study area, according to the existing standards and conditions, is a restricted area, which often corresponds to the eastern, northern and northeastern parts of Bojnourd. That is, the bed and river bed privacy of Firoozeh River, and the intersection of Halghehsang, Malkesh, Pesteh, Doberar, Aghghaleh, Gheshlagh, Langar, Baghchegh , Aliabad canals and the adjacent points of the Chaharkharvar-Babaaman, Doberar-Borj fault systems and the torn and hidden fault that it corresponds to the bed of Firoozeh river (Figure 2). From the total area of study area, 58.3 KM2 equivalent to 15.84% includes the ​​very suitable areas, which are mostly in the central (old army barracks), southern (upstream lands of the Mantagheh barracks, Maleksh and Takhte Arkan), southwestern (old police station) and southeastern parts (Hamzanlu, Kalateh Yavarie and Farhangian town) in the research area. Therefore, considering the current area of ​​Bojnourd, there is an optimal development space for the coming years based on moving in a low-risk path. The present study is based on a systemic approach and the application of geomorphological restricted areas and the research results for space management have the residential development efficiency for urban and suburban areas.
 
 





Condition:
Suitable areas
 
 
Very unsuitable areas
Forbidden areas
 
 





Figure 2. Map of forbidden areas and prospects for residential development in research area