Geospatial Technology in Urban Sprawl Assessment: A Review

Introduction

Urbanization can be defined as the migration or shifting of rural populations towards the urban areas. The major driving factors for rural to urban transition are industrialization, employment, better standard of living, and social security benefits (Aithal & Ramachandra, 2016; Bhatta, 2009). In the 21^st century, urbanization blooms as one of the biggest problems for many developing as well as developed countries all over the world (Jaeger et al., 2010; Muñoz, 2003). It is taking place at an unprecedented scale by creating profound impacts on the environment, economy, as well as the society (Sun et al., 2013). The foreseeable consequences of this process are the unplanned and uncontrolled spatial expansion of urban cores beyond their administrative boundaries in order to accommodate the growing population, which results in scattered patches or fringes (Marshall & Dolley, 2019). The sprawled cities are facing serious issues with respect to basic amenities, such as electricity, water, sewerage channels, transportation, and communication, along with a dramatic increase in pollution, poor health facilities, deteriorating educational standards, unemployment, and poverty. To overcome such issues, urban planners have to understand the dynamics of a particular urban area and the current urbanization process, which will solidify the basis of future predictions and guide in preparedness for urban sustainability (Anas et al., 1998).

There are three popular models for urban development, such as the concentric zone model (Burgess Model), the sector model (Hoyt Model), and the multiple nuclei model (Ullman Harris model). In the concentric zone model-based cities (e.g. Chicago, United State), multiple zones, such as industrial corridors, working-class housing, middle-class housing, and commuter zones with suburbs of higher-income-class housing are usually designed around a central business district (CBD). Whereas, the sector model-based cities (e.g. Sunderland, United Kingdom) are divided into multiple wedge-shaped (not ring shaped) sectors of transportation, industries, and low-medium-high-class residential areas designed around a central circular CBD. In both of these models, the CBD plays a vital role, however, in contrast, a less significant CBD is presented for the multiple nuclei model (e.g. Los Angeles and Houston). Multiple centres attract a particular kind of population, which is imitated by neighbourhood land use. Apart from these conceptual models, different countries develop their own theories and policies for urban development (Figure 1).

Figure 1.

Global trends of urban morphology

Several studies have been conducted to investigate the spatial heterogeneity and temporal distinctions of urbanizing trends in the small, as well as the megacities of the world collectively, and as individual continents i.e. for Asia (Enqvist et al., 2019, Friedmann & Sorensen, 2019; Masoudi et al., 2019; Lehner et al., 2016; Deuskar et al., 2015; Dutta, 2012; Gupta et al., 2012; Mohammad & Sidaway, 2012; Van Dijk, 2011; Griffiths et al., 2010; Kundu, 2011; 2006), Africa (Murphy & Carmody, 2019; Epstein, 1967; Little, 1960), and Europe, Latin America, the Caribbean, and North America (Dong et al., 2019; González & Medina, 2004). Hackenberg (1980) reported diffused and patchy patterns of urban expansion in South-Asian cities. However, Asian megacities in recent decades are experiencing a faster growth rate than the rest of the developed world. As a result, the peri-urban space around these cities of sprawl is of major concern due to irregular distribution of resources (Marshall & Dolley, 2019). Study of 129 European cities revealed very peculiar findings due to the process of re-urbanization and showed that economically revitalizing cities are experiencing disperse and thin centres with polycentric development (Salvati et al., 2019). On the other hand, smaller cities in Africa are comparatively less compact and more dispersed (Xu et al., 2019) due to physical constraints, poor urban policies, and irrepressible demography leading to sprawled urbanization and reduction in land use efficiency of the cities and their neighbouring area (Todes et al., 2010).