1. Introduction
Land use optimization is a key strategy for achieving long-term balanced urban growth through economic prosperity, resource efficiency, environmental protection, and social equality [
1,
2,
3]. Due to the involvement of multiple stakeholders, there are conflicting interests in urban land use optimization. For example, if residential development occurs in a low-lying area, it may solve the housing problem, but it will lead to the problem of urban drainage. If green space is replaced by urban buildings, due to urbanization, urban environment and health will be negatively impacted. Land developers want to maximize their economic profits while government tries to maximize social benefits from land use allocation. Different conflicting objectives are used in urban land use optimization problems. Some of the objectives are used most frequently in urban land use optimization problems. The most important objectives include maximization of economic benefits, maximization of ecological benefits, maximization of environmental benefits, minimization of land conversion cost, maximization of land value, maximization of land use compatibility, maximization of accessibility, maximization of compactness, maximization of ecosystem service value (ESV), and maximization of social benefits [
4].
Maximization of social benefits is one of the important objectives in urban land use optimization problems. Cities face a wide range of social challenges. The city develops as a unique interaction among inhabitants, contacts, social ties, and direct and indirect communication interactions, rather than just buildings, roads, parks, fences, abandoned corners, water lines, and cable networks [
5]. Concern regarding social well-being becomes a crucial prerequisite for a sustainable society and city. Social sustainability ensures equality, democracy, and diversity in our cities. In the present scenario of urban land transformation, urban ecosystem disturbance reduces the urban social efficiency of city space, which requires deliberate intervention to increase social interaction and public space [
6,
7]. For a city to be sustainable, it is mandatory that the city is socially linked through public space, design, and interaction regardless of social, cultural, and economic backgrounds which creates the opportunity for an accessible city. When a city offers a diverse range of opportunities for everyday life, it becomes more alive and appealing, which can improve the people’s quality of life. Furthermore, a socially sustainable city allows people’s health to be supported through urban places built for physical activity and socialization [
8].
In response to the growing concern of social well-being toward urban sustainability, many researchers included maximizing social benefits in urban land use optimization problems. However, in our previous study [
4], we identified that there is no generalized method to calculate the social benefit in the land use allocation problem. Many researchers tried to maximize social benefits in their land use optimization problems using different methods [
9,
10]. For example, Zhang et al. [
11] measured social benefit as a function of social security service value, Yuan et al. [
10] used the spatial compactness of an area as a measure of the social benefit, and Cao et al. [
9] considered spatial accessibility as an indicator of social sustainability. However, we argue that only a single indicator may not be the optimal measure of social benefit. Our claim is also supported by some other studies. For example, Jenks and Jones [
12] mentioned that although spatial compactness in the city has many social benefits, this compaction may lead to reduced living space, poorer access to green spaces, less affordable housing, and poorer health. Even a compact city may derive negative consequences if there exists incompatibility among land uses. If the land uses are compatible but there is a lack of accessibility, it will also reduce the social benefit. So, compatibility and accessibility are also the aspects of measuring social benefit. Similarly, there may be other indicators contributing to the measure of social benefit. Thus, we believe that multiple indicators can be attributed to the measure of social benefit. So, some kind of composite index is required to measure social benefit. However, in our previous study [
4], we identified that there is no such established method to measure social benefit in the land use allocation game. Against this background, this study aims to (a) identify the appropriate indicators as a measure of social benefit, and (b) propose a composite index to measure social benefit in urban land use allocation.
The rest of the paper is structured as follows.
Section 2 presents a brief literature review on the indicators used to measure social benefits from land use planning.
Section 3 describes the data used in this study and the methods followed for constructing the social benefit index (SBI). The result of this study is presented in
Section 4. This section illustrates the development of SBI. The section also contains the application of SBI in a real-world city. Finally, this paper ends with
Section 5, which contains the limitation, future scope of the work, and concluding remarks.
2. Literature Review
Urban land use planning is becoming a critical issue in the face of rapid urbanization and sustainability challenges. Sustainability has been the main concern in urban land use planning for the past decade. This emphasized the inclusion of environmental, economic, and social dimensions of sustainability in urban land use planning. Although the environmental dimension was the main concern in sustainable development in the early stage, debates within urban sustainability literature have moved beyond solely environmental concern to economic and social dimensions [
12]. A significant portion of the sustainable development literature now emphasizes the importance of considering social benefits in urban land use planning [
13,
14,
15,
16,
17]. For example, Eizenberg and Jabareen [
13] identified that social benefit was integrated late in the urban sustainable development debate, and they developed a conceptual framework to incorporate the social benefits into spatial planning. Medved et al. [
14] also explored that social benefits have received little attention in the built-environment discipline. In their study, they focused on the connection and interaction between urban planning and social sustainability. Williams [
16] worked on urban design and social benefits. He showed that better land use planning could ensure more social benefits to the residents, including a healthy, safe, accessible, friendly, and attractive environment.
To reflect the urban social sustainability, many researchers incorporated social benefits in their land use optimization problems and planning [
13,
16,
17,
18,
19,
20]. This section discusses different types of spatial indicators available in the literature to measure the urban social benefits.
A significant number of studies [
2,
10,
21,
22] considered spatial compactness as an indicator of social benefit. A systematic review on land use optimization by Rahman and Szabó [
4] showed that maximization of spatial compactness is frequently used as one of the optimization objectives in many urban land use optimization problems. In those studies, spatial compactness is used as an indicator of urban social benefits, thinking that a compact city is more sustainable and livable [
23], can maximize the social well-being of the people [
24], can provide better accessibility to city facilities; can promote social equity education, health, and living [
25]; and can offer a higher level of personal satisfaction, social interaction, and perceived physical health benefits [
26]. However, this indicator alone cannot be sufficient for measuring social benefit because other studies show that although spatial compactness in the city has many social benefits, this compaction may lead to reduced living space, poorer access to green spaces, less affordable housing, and poorer health [
12]. So, in addition to spatial compactness, other indicators should be considered while measuring social benefits. Different methods were used to measure urban spatial compactness. The most common methods used to measure spatial compactness include (a) non-linear integer program-neighbor method; (b) linear integer program-neighbor method; (c) minimization of shape index; (d) linear IP using aggregated blocks/minimization of the number of clusters per land use types; (e) linear integer program using buffer cells; and (f) spatial autocorrelation [
27]. The non-linear integer program is the simplest explanation for land use compactness, which relies solely on the neighbors of each cell to calculate compactness by sum. The linear integer program model is an analogous linear reformulation of the first, with the inclusion of integer variables [
28]. The minimization of shape index method calculates each cluster’s form index, which sounds complicated but it is a good way to describe compactness [
29]. The fourth concept is to group individual cells into blocks and create a model that reduces the number of blocks in the final allocation result that contains only one land use category. In other words, the goal is to reduce the number of clusters by as much as possible for each land use category. The fifth method is stated as a problem in which parcels are chosen, and each reserve (one land use type) is divided into core cells and a buffer zone. Compactness is achieved indirectly by reducing the number of buffer cells surrounding the core sections [
30]. The last option is to use Moran’s I, and other geographical statistics to calculate spatial compactness [
31].
The land use compatibility is considered a crucial factor in urban development planning. It refers to the situation in which adjacent land uses can co-exist without creating any negative effects. Land use compatibility has a strong connection with many aspects of social gain in cities. Hence, it is considered to be another criterion of urban social benefit in relation to land use planning. Land use compatibility is used in many urban land use optimization problems and planning, thinking that compatibility among adjacent land uses will derive more social benefits to the urban people [
3,
32,
33,
34,
35,
36]. Land use compatibility has significance in social sustainability and social well-being through increased social interactions, good human–environment interaction, a pleasant and healthier environment, and increasing livability [
35]. Although a compact city generates many social benefits, it may degrade the health and livability of people and derive more negative consequence if there exist incompatibility among land uses, for example, industrial activities beside residential land [
37]. If there is a lack of compatibility among the adjacent urban land uses, it may lead to incongruous urban land development, and a polluted environment [
38]. Effective urban planning and social benefits can be achieved if urban land uses allocation is happened in an ideal situation to avoid negative impacts from adjacent land uses. Adjacent land uses may create negative externalities on other land uses through inter-land use interaction if the spatial structure of land uses is incompatible to each other [
39]. So, land use compatibility is an important factor of urban social well-being. Different methods, including the score card method, expert opinion method, analytical hierarchy process (AHP) method, Delphi method, etc., are used to derive the compatibility of land uses. While the main principle of deriving the compatibility values is the judgment of the expert in the respective field, the computation method is somewhat different. However, the most widely used method to derive compatibility value is AHP [
40] since this method is straightforward. In this method, land use types are compared on a scale between 1 and 9 based on a group of experts. Based on the pairwise comparison, the final compatibility value is derived.
Land use mix is a widely discussed subject of social sustainability and overall urban sustainability. It refers to the degree of diversity among the different land use types within an area. Land use mix is considered a measure of social benefit since the land use mix provides many benefits to the city. These include short trip generation, easy access to facilities, reduced transport cost and travel length, reduced emission, etc. It is an important component of walkability [
41]. The capacity to locate different types of functions (residential, commercial, institutional, and recreational) within walking or cycling distance is a benefit of mixed land use. Land-use policies have shown that mix-use design is a good method to promote non-automobile forms of transportation [
42]. At the microlevel, Gehrke and Clifton [
43] stated that mixed land use as a strategy has a substantial association with walking. Other studies have also found a link between active commuting, accessibility, and walkability through mixed land use [
44]. It is one of the foundations for urban sustainability against functional segregation in land use policies. In many studies, land use mix is considered an integral part of land use allocation problem and planning on the reasoning that mixed land use promotes social well-being of urban population [
45,
46,
47]. Mixed land use is a prerequisite for urban proximity dynamics, healthier lifestyles, and public space vitality [
48]. Land use mix has significance in deriving social well-being and benefits from urban land use allocation. Mixed land uses promote walkability, shorten trip length, reduce emission, save energy and resources, ensure effective use of urban infrastructure and services, and increase social interactions [
49]. The quantification of land use mix can take numerous forms. One method is to quantify the degree of land use mix and investigate the relationship between built environment characteristics (such as urban density, distance, destination accessibility, and transportation network structure) and individual movement in cities [
50]. Different methods, including clustering index (CLST), activity related complementarity index (ARC), balance index (BAL), entropy index (ENT), Herfindahl–Hirschman index (HHI), dissimilarity index (DIS), Gini index (GINI), and mixed degree index (MDI), are used to measure land use mix in a city [
51]. However, the CLST, ARC, MDI, and GINI indices were seen in limited use in the literature due to their limitations. The ENT, DIS, and HHI were found to be the most successful methods for quantifying land use mix in most of the research. Previous research has employed the ENT to determine the land use mix status. The term ENT refers to an area that has a mix of different forms of land use. The HHI refers to the land use mixed status and is used to describe a state of market concentration. DIS, according to researchers, is a method of determining the balance status of a specific area’s land use mix [
52]. However, due to the computation simplicity and more meaningful applicability, the ENT is discussed and used widely in many research works as a way of presenting the diversity of land use mix. The spatial distribution of population in the city is another criterion to measure social benefits that people gain from the city. Cities provide many functions and opportunities to the urban people. In welfare economics, the functions and benefits that people derive from the city are known as utility [
53]. Studies suggest that spatial distribution of population within a city has a strong relationship with health and the social well-being [
54]. This requires the population in city to be distributed in such a manner that can maximize the per capita utility from the city. If the population distribution is not optimal or homogeneous, then it will create spatial disparity in social benefits of the city people [
55]. For example, if there are two green spaces of similar size and functions in a city but if these green spaces have different coverage area and serve different numbers of population, then the per capita utility values from the green spaces will be different, which may create spatial disparity in terms social benefits and well-being. Similarly, if the population density in a given area is more or less than the ideal population density then the resources (public utilities, open space, health facilities, etc.) will be either burdened or underutilized. So, optimal population distribution is important to maximize the per capita utility or social benefits within the city. Evenness is one of the techniques to measure the homogenous distribution of any geographical phenomena. Evenness expresses how evenly the individuals in the community are distributed over the different species. Different methods are used to measure the evenness in the spatial distribution. These include the Alatalo evenness index, Menhinnick evenness index, Simpson’s dominance index, Shannon–Wiener evenness index, etc. [
49]. All these indices use block or zone to represent the evenness of distribution. One problem with these methods is that they cannot be applied in a single cell considering the attribute of the cell concerned. Rather, multiple cells forming zone are used to calculate the value of evenness.
The above literature suggests that several factors are linked with urban social benefits. A single indicator alone cannot reflect the social benefits from land use allocation. Hence, multiple indicators are required to measure the social benefits.