Scenario Making for Land Subdivision in the Urban Development ProcessCase Study: Marginal Area of Semnan

Urban development planning has always faced new challenges with regard to increasing complexities in the decision-making environment which makes it necessary to use new methods for predicting and preparing for the future. In this regard, as a new approach, the planning based on making scenarios will help identify and present different scenarios for making specific decisions in urban management. In the process of urban development, the subdivision of land has always been a controversial topic with regard to new developments and several factors have been involved in determining the size of the area of the desired parts. In the present study, the four factors of household dimension, income level, land price, and accessibility to urban centers were selected as independent variables and land area was selected as the dependent variable. The results of the significance of each independent variable in explaining the dependent variable have been presented in a regression relationship. The region under study is Semnan city which, according to the predictions of the comprehensive plan horizon (2026), will need 86 hectares of land. The land subdivision modeling process has been done in seven steps and the basic tool used to divide the land is the model presented by Dahal and Chow (2014) which divides large pieces of land fully automatically based on size, shape, and direction. Considering the variables and relationships presented to determine the size of separation segments, four possible scenarios are obtained and finally, according to the characteristics of the city of Semnan, the probable scenario that is based on accommodation of low and medium level of income in margin area of city has been chosen and the pattern of subdivision is presented. IntroductionComplexity and multi-dimensionality of the urban development process have made its analysis difficult leading to uncertainties and the probability of occurrence of various futures. the planning based on making scenarios is one of the common ways to deal with uncertainty in the environment. Unlike traditional planning methods, this approach develops potentially different views of the future and thus provides a basis for creating solutions and options that are suited to different situations. In the planning of urban development, land subdivision is considered as the first stage of design. Investigating and analyzing the effects of different patterns of land subdivision in a vacant land plot is an important part of urban development projects. Because of the various economic, social, and physical factors involved in the process of land subdivision, the need to examine their impacts is necessary. In this regard, the purpose of the present study is to apply the factors affecting the subdivision of land plots and the presentation of its various patterns in the process of urban development with the approach of making scenarios. The basic tool used in this regard is the model developed by Dahal and Chow (2014). This model is based on vector space and divides the land fully automatically. Based on this, different patterns of land subdivision have been presented in different scenarios and considering the characteristics of the case study (Semnan city), the probable scenario has been chosen. MethodologyThis research is applied in terms of purpose and is descriptive-analytical in terms of method. The proposed modeling for land subdivision in the developed areas of Semnan up to the comprehensive plan horizon (2026) is carried out in seven steps:Step 1: Calculating the amount of land needed to develop the city in the comprehensive plan horizon (2026)Step 2: Determining the blocks in the developed margin area Step 3: Determining the spatial value of each of margin blocksStep 4: Providing a regression relation according to the factors affecting the size of the segments of the landStep 5: Predicting income growth and land price in the comprehensive plan horizon (2026)Step 6: Providing different scenarios for land division in the comprehensive plan horizon (2026)Step 7: Conclusion and selection of the probable scenarioResults and discussionIn this research, presenting different scenarios has been done through statistical methods. On this basis and considering previous studies, accessibility, household dimension, land price, and household income level were selected as the main factors affecting the determination of the area of land segments, and the effect of each of them was determined based on a regression relation in Semnan city. On the other hand, each identified margin block has a different spatial value considering the two factors of accessibility and land price and the households tend to live in one of the margin blocks according to their economic power and suitability so that it was assumed that higher-income households will live in blocks with higher land prices and better accessibility. Assuming that the regression relationship in comprehensive plan horizon (2026) holds and considering the spatial value of each block, four different scenarios were presented for the subdivision of land segments using Dehal and Chow’s model (2014). ConclusionIn order to select a scenario which is more consistent with the future conditions of urban development in Semnan, the views of real estate agencies (6 real estate agencies) and 4 urban planning experts of Semnan municipality were used. Real estate agencies were asked to choose the probable scenario according to land price, land sale, mortgage, rent, and area of existing segmented lands in the margin neighborhoods of Semnan such as Rozieh Town, Janbazan Town, 400 Units and Mehr Housing Units, and also according to people’s living standards and their willingness for housing in these neighborhoods. In addition, the urban experts of the municipality were asked to choose the desirable scenario by considering the population increase of Semnan city by 2026, the settlement of the immigrant population, land price, the number of licenses issued for construction, the lack of facilities and land uses, and, finally, the economic, social, and cultural characteristics of the inhabitants of margin neighborhoods. By summing up the obtained comments, scenario number four seemed the most likely option from the view of most experts.