Study on the Implications of the Function and Role of Urban Areas on Population Projections in the Formulation of Detailed Spatial Planning (RDTR)

: The initial and crucial stage in the spatial planning process involves identifying the function and role of a region or area. This step sets the course, establishes goals, and defines the parameters for the subsequent spatial arrangement planning. Currently, the expedited development of Detailed Spatial Planning in Indonesia is closely tied to the function and role of an area, which is influenced by numerous factors that require careful consideration. This study aims to compare population projections using conventional projection methods with projections that take into account the functions and roles of the region. This study uses population projection analysis, population development scenarios, and spatial availability analysis to assess the differences in spatial projections that can accommodate population growth. The calculations unveiled a significant disparity between population-based projections and projections that consider the functions and roles of a city/area. This input is crucial for assessing spatial needs and the necessary infrastructure and supporting facilities that will be incorporated in the formulation of the structure and spatial patterns of Detailed Spatial Planning. Hence, when estimating population projections, it is essential for planners to consider projections that incorporate the functions and roles carried out by the area


INTRODUCTION
Defining the function and role of a region or area is a fundamental element that underpins the process of spatial planning (Moseley, 2013). The process of defining the function and role of a region or area is influenced by various factors and involves multiple parties (Tulumello et al, 2020). In terms of governance and development policies, different stakeholders (government levels and sectors) have their own interests they seek to fulfill in a particular region (Faludi, 2013). Occasionally, the policies of various parties work together harmoniously, resulting in successful development in the intended region/area. However, there are instances where the anticipated synergy does not occur, leading to the nonfulfillment of the designated functions and roles. An example of this is the large-scale conversion of agricultural land into housing areas, which has the potential to threaten food security. This happens because the definition of the region's function and role is still vague and abstract. Therefore, it is necessary to provide a more detailed description of the interrelationships between the functions and roles of regions/areas. The effects, influences, and implications resulting from the establishment of functions and roles should be clarified and comprehended by all stakeholders during the planning process, particularly when calculating population projections. Nevertheless, population projections will influence the spatial needs of a specific region/area, especially in the current era of Detailed Spatial Planning (RDTR) (Hamidah et al, 2019;Mundia & Aniya, 2005).
Environmental damage, rising crime rates, and social disharmony in a region/area are manifestations of the improper implementation of the functions and roles of that area (Faludi, 2000). As an example, uncontrolled development leads to higher carbon emissions, traffic congestion, and air pollution, which are prevalent issues in numerous cities in developing countries like Indonesia, the Philippines, and India (Lebel et al., 2007). As an example, when a city's functions and roles are not balanced in relation to its environmental capacity, it leads to a decline in environmental quality due to unregulated land use changes. For instance, in the study (Chen et al., 2021), strict regulations are implemented to control agricultural activities in a specific area, aiming to prevent unregulated land conversion. Similarly in Britain, the government actively avoids the conversion of agricultural land into industrial areas. However, the designation of agricultural areas is carefully regulated through various indicators, ensuring that the delineated agricultural zones are preserved and protected from conversion.
"High-quality farmland is primarily concentrated and distributed in Wangcheng, Ningxiang, and Changsha in northwest Changsha City. Therefore, only high-quality farmlands were classified as basic farmlands for effective protection".
The concentration of various activities in urban centers has led to imbalances among the surrounding areas. In a different scenario, the expansion of industrial activities can result in a significant increase in population due to the availability of employment opportunities in the industrial sector. However, the growth of the industrial sector does not necessarily translate into support from other sectors, particularly housing, especially for the labor force (Carmona, 2019;Chen et al., 2021;Hersperger et al., 2018). As an example, in some industrial areas, the need for housing has increased dramatically. Eventually, slums emerged to accommodate migrant workers in the vicinity of industrial zones. The aforementioned examples demonstrate how unforeseen consequences of a function and role can result in less-thanoptimal outcomes. From an economic standpoint, the overemphasis on the function and role of a specific area or the ineffective implementation of functions and roles can result in economic losses. This can occur when infrastructure, which has already been constructed, remains underutilized and fails to meet the intended targets (Lebel et al., 2007;Sitányiová & Masarovičová, 2021).
It is crucial to carefully consider the population size that arises as a consequence of fulfilling the function and role of a region/area when making such determinations. In the process of spatial planning, population estimation frequently relies on projections derived from the prevailing population growth trends. In practical terms, there are often discrepancies Nasution et al,Study on Implications….. 53 between projected population estimates for the future and the actual outcomes, primarily due to inaccuracies in effectively implementing the function and role of regions/areas (Tulumello et al., 2020). The employment multiplier approach is a commonly employed method for estimating population, wherein an expansion of the workforce in a specific sector leads to the proliferation of employment opportunities across other sectors (Pangastuti, 2015;Zenda, 2017).
Simplifying the concept, the addition of workers in the primary sector leads to an expansion of the workforce in the service sector. It is essential to conduct a comprehensive analysis of this addition to effectively anticipate meeting essential societal needs, including housing, clean water, electricity, and other vital requirements.
Spatial planning faces a similar dilemma in various other countries, posing diverse challenges, particularly in terms of ensuring the availability of fundamental infrastructure (Tulumello et al., 2020). This analysis plays a critical role in making informed decisions and considerations for the future (Feltynowski et al., 2018;Wang et al, 2019). As a result, numerous studies are actively exploring ongoing efforts to improve the efficient and sustainable management of regions (Chen et al., 2021;Longato et al, 2021).
Presently, the formulation of Regional Spatial Planning (RDTR) in Indonesia is undertaken as an effort to regulate and manage urban development in a systematic and efficient manner, preventing random and inefficient growth. The process of organization becomes increasingly challenging due to a combination of factors (Sutaryono & Dewi, 2022), such as inadequate control mechanisms, high land prices coupled with limited government budget for compensation, and ambiguity surrounding land ownership status, whether it belongs to the government or the public (Havel, 2014). Hence, in numerous countries, the effectiveness and clarity of land-related regulations play a pivotal role in achieving successful spatial planning. However, at present, the implementation of real zoning management restrictions on urban development is not evident in the planned outcomes in Indonesia. To this day, there is a lack of comprehensive studies that specifically address RDTR, particularly after the issuance of the Omnibus Law on Job Creation No. 11 of 2020 with its derivative regulations. As a result, conducting a study on the function and role of cities becomes crucial in the process of developing RDTR, as it can provide guidance for more structured and sustainable development.
The Urban Market Area in Batang Anai Sub-district, situated in Padang Pariaman Regency, West Sumatra Province, is officially designated as one of the urban areas outlined in The examination will focus on the implications of assigning the function and role to the Urban Market Area of Batang Anai from the perspective of population growth. How many employment opportunities will be generated when the function and role of this area are fully realized? The identified functions and roles that have a significant impact on the resulting population are as follows: serving as a hub for the processing industry of agricultural products, functioning as an agropolitan area, particularly in the development of Sustainable Food Agriculture Land (LP2B) encompassing more than 20% of the area, providing residential areas for individuals employed in the city of Padang and its neighboring regions, and serving as an urban area with various service-related activities. These functions and roles are deemed influential in determining the population that will be generated in the area.

METHODS
The designation of a region's function and role in the spatial planning process is highly significant and must be carefully considered. This is because it has implications for the spatial requirements of various aspects, such as residential areas for the population, public and social facilities, as well as other necessary infrastructure.
The required data for this research comprises a collection of documents containing policies and guidelines concerning the function and role of the Urban Market Area. These documents encompass the Regional Spatial Plan (RTRW) of West Sumatra Province, the RTRW of Padang Pariaman Regency, the Medium-Term Regional Development Plan (RPJMD) of West Sumatra Province, the RPJMD of Padang Pariaman Regency, as well as other pertinent policy documents. Furthermore, it is necessary to obtain various statistical data that portray the state of the Urban Market Area, and these data can be obtained from Statistics Indonesia (BPS). Additionally, spatial data depicting the geographic condition of the Urban Market Area is also needed. In addition to the aforementioned data requirements, it is also feasible to collect information from informants regarding the implementation of development policies for the expansion of Pasar Usang Urban Area.
The methods used involve reviewing relevant literature on government policies at the national and regional levels concerning regional development, particularly focusing on the function and role of Pasar Usang Urban Area. Furthermore, statistical data analysis and thematic mapping are employed to examine social and economic characteristics. Moreover, descriptive analysis is conducted based on interview findings and discussions with informants to address the issues and future development plans in the Urban Market Area.
To address the implications of the function and role of a city on population growth, it is necessary to compare population trends based on population projection formulas and population projections based on scenarios related to the functions and roles undertaken, such as industry and agriculture. Some of the methods employed to analyze population projections in this study are: 1. Population Projection Analysis is conducted to examine the future population growth.
This analysis will be used to compare population growth with the current trends, without the intervention of the development of the function and role of Pasar Usang Urban Area. The population growth using the exponential method is chosen because this method represents a gradual increase in population throughout the year, unlike the geometric method which assumes that population growth only occurs at one specific moment during a certain period of time (Adioetomo and Samosir, 2010). In addition, this method can also lead to overestimation if there are specific policies or factors that influence it (Davis, 1995;Gulseven, 2016). The formula used in the exponential method is: To obtain the population growth rate (r), the equation is used.

Characteristics of the Region
The Delineation of the Detailed Spatial Plan for Pasar Usang Urban Area is designated with an approximate area of about ± 4,789 hectares. The area covers parts of the administrative regions of several Nagari in Batang Anai Sub-district, namely: Nagari Kasang, Nagari Sungai Buluah Selatan, Nagari Sungai Buluah, Nagari Sungai Buluah Timur, Nagari Sungai Buluah Barat, Nagari Sungai Buluah Utara, Nagari Buayan Lubuk Alung, and Nagari Katapiang. For a clearer understanding, Pasar Usang Urban Area is based on Nagari can be seen in Table   1.

Land Use
Pasar Usang Urban Area, which is planned to become a supporting urban area for the city of Padang, is currently predominantly characterized by undeveloped lands such as forests, rice fields, farms, and plantations ( Figure 2). Only 17.44% of the entire urban area consists of developed land, including residential and industrial areas (

Population Profile
An overview of this population profile is based on the development of the number of residents in Batang Anai District. In Table 4, population projections are carried out over the next 20 years. In Sungai Buluah village there was an expansion into five villages/Nagari, so there was a change in population data after the expansion.

Analysis of Population Development Based on Tendencies
As mentioned in the methodology section, it is crucial to take into account the function and role of an urban area when making population growth projections.
Specifically, the analysis will delve into the functions and roles, and their implications will be examined using specific analytical tools and assumptions outlined below.
As mentioned earlier, due to the unavailability of precise population data for this area, the population projection of the Batang Anai Subdistrict is utilized as a foundation for

The Utilization of Labor in the Industrial Sector
Serving as a hub for industrial activities, a total area of 435 hectares is designated for industrial purposes in the Pasar Usang Urban Area. According to the Technical Guidelines for Industrial Area Planning, the employment capacity of an industrial area is estimated to 62 BHUMI: Jurnal Agraria dan Pertanahan, 9 (1), May 2023 be 100 workers per hectare. Additionally, it is assumed that 70% of industrial workers will form households, with an average of 4 individuals per household in terms of population count. In the beginning, the percentage of supporting workers is 20%, and it increases by 5% every 5 years. As a result, by the year 2038, supporting workers will constitute 40% of the total industrial workforce.
The local population of the core area comprises individuals living in the Bahodopi and Bungku Timur sub-districts, as indicated by statistical data.
The estimation of labor absorption in the industrial sector is based on assumptions outlined in the Technical Guidelines for Industrial Area Planning. Considering the industrial area's expansive size of 435 hectares, it is expected to generate employment opportunities for approximately 43,500 workers. Assuming that this industry serves as the primary sector, it will have a positive impact on the growth of the non-primary sector, with a ratio of 60% for the primary sector and 40% for the non-primary sector. Consequently, the non-primary sector is projected to employ around 30,000 workers, resulting in a total workforce of approximately 70,000 workers. Considering the equivalent number of households, which is estimated to be 29,000 households or approximately 116,000 residents.
This implies that 29,000 housing units are required to meet the housing needs of these workers. Certainly, these calculations can be even higher when considering the growth in other sectors (Zenda, 2017).

The utilization of labor in the food agriculture and plantation sector
Its role is to serve as an agropolitan area, with significant sub-sectors including food crop agriculture (LP2B paddy fields) and smallholder plantations. Taking into account various studies (Isbah & Iyan, 2016;Sudalmi, 2009), this analysis assumes that the absorption capacity for agricultural land, specifically paddy fields for food crops, is estimated at one farming family per hectare. Regarding this matter, it should be noted that the average number of individuals per household in the Batang Anai District is 3.8, which can be rounded up to 4 individuals per household. Additionally, in the smallholder plantation sub-sector, the labor absorption follows a similar pattern to that used in transmigration areas, where one transmigration household is capable of cultivating 2 hectares of land.
Considering its role as an agropolitan area, the projected population will be determined based on the number of households, with an assumption of an average of 4 individuals per household.
In the food crop agriculture sector, particularly in the management of LP2B (rice fields), the assumption is that one farming household is responsible for one hectare of paddy field. Therefore, with a land allocation of 1,024 hectares, it will accommodate 1,024 farming households. Moving on to the plantation sector, the assumption is made that each transmigration household requires 2 hectares of land per farmer. The allocation of 1,167 hectares of land for smallholder plantations will provide space for 584 farming households.
The combined agricultural sub-sectors will provide employment for 1,608 farming households, which corresponds to a population of 6,430 individuals.

Labour Multiplier Analysis
Serving as an urban service center, this area will witness the construction of diverse infrastructure and facilities to support urban life as part of the urban development policy.
To address employment absorption in this context, the labor multiplier approach will be employed, which strongly correlates with the development of base sectors such as industry, agriculture, and housing (specifically dormitory). Given the urban-rural theme of the area's development, it is expected that the base sectors will continue to have a higher employment absorption compared to the service sector. In this study, a ratio of 60:40 will be used, indicating that for every 3 workers in the base sectors, 2 workers will be generated in the service sector. Additionally, the estimation of population and households will take into account assumptions related to other functions and roles. Taking into account the labor multiplier approach and assuming a 60:40 ratio between the base sectors and the service sector, the urban service sector is estimated to absorb approximately 21,426 workers. This is derived from the assumption that the base sectors will employ around 30,608 workers, with the remaining proportion being allocated to the service sector. Assuming that the ratio of workers to households in the service sector is similar to that in the industrial sector, we can expect the creation of approximately 14,284 households from the service sector workforce.
The analysis of each sector, which serves as the foundation for the functions and roles of the Pasar Usang urban area, indicates that a significant number of job opportunities, totaling 52,034, will be available. Consequently, this employment growth is expected to lead to the formation of around 44,892 households, accommodating a population of approximately 179,568 individuals.

Housing Area Capacity Analysis
Function as a residential area. Considering the urban-rural concept that will be implemented in this region, the allocation of space for the residential zone encompasses two subcategories: medium-density housing and low-density housing. In order to calculate the density of medium-density and low-density housing, an analysis is conducted to assess the size of residential plots that serve as the basis in this region. As per the decree issued by the Regent regarding the minimum plot size in this urban region, it is determined to be 87 square meters per plot, which is rounded up to 90 square meters per plot. Additionally, for low-density housing, a plot size of 200 square meters per plot will be utilized as the foundation for calculating the capacity of the allocated space.
In order to assess the housing capacity, considering the housing density that will be provided, we utilize the assumption of a minimum plot size (90m 2 ) and a standard plot size (200m 2 ). Based on the calculation, where 60% of the residential land area will be allocated for house plots, it is estimated that medium-density housing will be able to accommodate

Increase Due to Functions and Roles
The analysis of population growth based on existing trends reveals a substantial gap between the projected population to be accommodated through the development of Pasar Usang's urban functions and the current population growth rate. The implications of this development indicate that the population is expected to almost double compared to the existing growth trend. This indicates the importance of carefully considering the establishment of functions and roles for an area. This also has an impact on the demand for supporting infrastructure, such as clean water supply (Lebel et al., 2007).
The estimation of the population for a developing area with specific functions and roles can no longer rely on the existing population growth trends alone. Therefore, it is essential to enhance the information and refine the assumptions used to calculate the workforce implications that will arise from the development of a specific function in an area. When developing an area based on development themes, it is crucial to take into account the workforce implications that will be generated. Additionally, this will contribute to the planning and development of essential infrastructure and amenities to enhance the quality of life for future residents in the designated area.

Comparison of Population Development with Housing Capacity
The inaccuracies in calculating the carrying capacity of an environment have resulted in unfavorable outcomes, with many developed areas exceeding their carrying capacity and capacity limits (Duh et al, 2008;Henry, Yongsheng, & Jun, 2006). The approach of considering the housing capacity for an area can be used to establish the threshold for development activities in a particular region. In this study, the housing capacity derived from the allocated space for housing as defined in the Spatial Planning Document for Pasar Usang Urban Area will be used to assess whether the designation of the area's functions and roles will exceed the environmental carrying capacity or not. Based on the calculation of housing needs derived from the employment absorption of the area's functions and roles, which amounts to 44,892 houses, it can be concluded that the designation of the area's functions and roles is still below the housing capacity of 78,983 units. This allows for the opportunity to develop the functions and roles of the Pasar Usang urban area as a dormitory town, which will be part of the Padang metropolitan area.
The above discussion indicates that there are several important factors to consider in determining the functions and roles of a city, including the absorption of labor according to the city's functions and roles, which can generate population growth even beyond the projected population calculations using standard methods such as arithmetic, geometric, or 62 BHUMI: Jurnal Agraria dan Pertanahan, 9 (1), May 2023 exponential projections. This aspect is often overlooked in the preparation of a planning product.
By examining other studies conducted in various countries to analyze urban development, several other factors can also be taken into consideration in determining the function and role of this area. These factors include interregional interaction, accessibility, and mobility analysis, land use distribution and development, density structure, urban activities and planning, and relationships with surrounding areas (Shen & Karimi, 2016;Willemen, Verburg, Hein, & van Mensvoort, 2008). As a result, the Urban Function Connectivity (UFC) method has been developed to further study the functions of this area in-depth (Shen & Karimi, 2016). This can also be further examined in future studies. With the acceleration of the spatial planning document (RDTR) preparation in Indonesia in the next five years, there are many aspects that still need to be thoroughly studied, especially in strengthening the substance of this RDTR.

CONCLUSION
Based on the discussions and findings of this research, several conclusions can be drawn as follows: First, based on the natural conditions, geographical location, and existing development policies, the Pasar Usang Urban Area has been designated with the following functions and roles: an industrial activity center, an agribusiness activity center, an urban services center, and a dormitory town that is part of the Padang metropolitan area.
Second, there is a significant difference in population growth in this area between calculations using exponential projections and calculations based on the scenarios of the functions and roles of the area, which in this case are industry, agriculture, and housing.
This illustrates that it is not appropriate to rely solely on projections based on existing trends as a basis for estimating the population in new development areas for spatial planning purposes.
Third, the implications of these calculation differences emphasize the importance of assessing the carrying capacity and capacity of an area when considering any development interventions. Among these is the need to project the necessary infrastructure and facilities required in the area. This includes anticipating the required provisions for infrastructure in the region.
Some limitations of this study include the use of assumptions that need further investigation, particularly in the context of other cities. This also acts as feedback for future research to enhance the development of stronger assumptions that are employed.
Nevertheless, this study is crucial for the formulation of spatial planning, especially in the current era of accelerated RDTR.