Introduction

Urbanization refers to an irreversible physical process involving large scale land cover changes of an area with an increase in the number of people living in it as well as an increase of its built-up density (Maiti et al., 2005; Ramachandra et al., 2012), that would thereby affect the area’s ecology and environment. The urbanisation process has gained momentum during the last two decades due to globalization and its accelerated economic activities. Employment opportunities at urban centers have been a catalyst in causing large scale migrations from rural to urban pockets. As a consequence to intense urbanisation at core regions, dispersed growth or sprawl occurred at peri-urban areas and city outskirts. As this growth was not visualized during the planning process, most sprawl regions are now devoid of basic infrastructure facilities and amenities such as treated water supply, sanitation, electricity, etc. (Sudhira et al., 2004; Ramachandra et al., 2012). Usually, sprawl occurs along urban fringes, at the edges of urban areas or alongside highways.  Sprawl generally alters regions by imbibing in them a highly fragmented urban morphology; agricultural lands, open spaces, and ecologically sensitive habitats are all disturbed in the process. Some of the causes of sprawl include population growth, economic factors, civil activities such as construction of buildings and roads, and development of infrastructure using taxes. Thus, urbanization dramatically changes the rate of growth of urban areas with the core center of the city bearing simple and compact urban features whereas the urban fringes or suburban regions tend to become more complex and diverse thereby reflecting a highly fragmented urban morphology. The trend analysis of urban growth helps us to understand the spatial patterns of the built-up area and sprawl.

Many towns in India are growing fast due to various infrastructural developments. The urban population in India is presently growing at the rate of 2.3% per annum.  The global urban population has increased from 13% (220 million in 1900) to 49% (3.2 billion, in 2005),  and  it is  projected  to  escalate to 60%  (4.9 billion)  by  2030  (Ramachandra  and Kumar, 2008; World Urbanization Prospects, 2005). The increase in urban population in India in  response  to  the growth  in  urban  areas  is  mainly  due  to  migration.  There  are  48  urban agglomerations/cities  in India having  a  population  of more  than  one million  (in  2011). However, in 2001, the number of these agglomerations was only 30. It has been projected that more than half of the world’s population will become urban dwellers as the urban population is expected to reach 81% by 2030 (United Nations Population Fund).

The main problem of unplanned urbanisation is sprawl by which there are conversions of urban-rural fringes into urban areas although without basic facilities and amenities. Urban sprawl is currently occurring at an unprecedented rate that is having a marked effect on the natural functioning of the immediate environment (Turner et al., 1994). Sprawl is generally associated with the loss of all environment-friendly land uses and is proportional to the increase of urban density in small spatial locations in and around urban areas due to lack of integrated and holistic approaches in regional planning (Sudhira and Ramachandra., 2007; Ramachandra et al., 2012). The landscape undergoing unplanned growth due to various anthropogenic activities requires to be monitored to understand the rates of changes in urban land use (Peiser, 2001, Stow and Chen, 2002). Monitoring urban structure brings out the various spatial characteristics of the land surface apart from elucidating the impacts on the surrounding environment (Yeh and Li, 1999; Lillesand and Keifer, 2002; Sudhira et al., 2004; Ramachandra et al., 2012). In rapidly urbanizing regions, there are mass migrations of people from rural areas to urban areas and also from smaller towns to urban metropolises. The process of urbanization in India gained momentum with the industrial revolution of 1970’s, followed by globalization of 1990’s, both of which caused the disappearance of other land uses (Rahman, 2007) affecting local ecology and environment.

This rapid urbanisation has demanded immediate interventions through inventorying, mapping and monitoring of various advanced mapping technologies such as remote sensing and satellite technologies (in order to understand the dynamics of land uses). The usage of these technologies help the city administrators and planners understand the problems which accompany such urban processes (Maktav et al., 2005; Bhatta et al., 2009; Ramachandra et al., 2012). The temporal spatial data acquired through space-borne sensors help in the understanding of urban growth pattern, urbanisation rate, and the underlying problems of urbanisation such as urban sprawl. These, ultimately, aid in better administration by assisting in garnering basic amenities (Ramachandra et al., 2012). Urban sprawl has been characterized considering indicators such as growth, social conditions, aesthetics, decentralization factor, accessibility conditions, density, open space availabilities, dynamics, costs, and social benefits. (Bhatta et al., 2009, 2010). Further, Galster et al. (2001), have identified additional parameters for quantifying sprawl which are density, continuity, concentration, clustering, centrality, nuclearity, proximity and mixed uses. In this study, firstly, the pattern of the land use changes has been studied temporally using remote sensed satellite data. Landscape metrics were computed to quantify the patterns of urban dynamics (McGarigal and Marks, 1995). These spatial metrics capture the dynamics of the land surface under consideration (Gustafson, 1998; Turner et al., 2001). These metrics are been used as indicators of the pattern of land surface changes (Herold et al., 2002; Herold et al., 2003; Zhang et al., 2004; Angel et al. 2007: Jiang et al. 2007; Taubenbock et al., 2008a; Taubenbock et al., 2008b; Bhatta et al., 2010; Ramachandra et al., 2012). Further, in order to understand the local patterns of growth, density gradients were obtained which provided the localized information on the land use pattern (Torrens and Alberti, 2000; Ramachandra et al., 2012).These studies confirmed that temporal remote sensing data with gradients and spatial metrics’ techniques provide the accurate and detailed understanding of urban structure at local levels that are necessary for effective urban planning.

The main objective of the current study is to understand the underlying land use dynamics using temporal remote sensing data along with spatial patterns of urban growth through density gradients and spatial metrics.