Assessment of differential urbanization using spatial entropy model for Tiruchirappalli urban and tier towns, India

Urban sprawl is associated with many urban centres across the world; many times, the impacts are found to be negative on living organisms and the natural environment. Quantification of urban has been a valuable field of study to understand its various factors like dispersion, density, diversity, dimension, and many others. To be resilient and sustainable, many of these cities need to be physically restructured, which is quite an impossible task, especially in developing countries like India; Although, instead of restructuring established urban centres, plans can be developed to focus on the growth of the surrounding tier urban centres. The objectives of the present study are to, (1) assess the changes in the urban growth and built-up density; (2) assess the urban diversity of the Tiruchirappalli Municipal Corporation and the tier urban centres on a temporal scale for the years 1996, 2008 and 2020. The study has been carried out with the use of Landsat 5 and 8 satellite images. The hierarchical unsupervised image classifier technique is used to classify the image and the study area has been split into eight zones in which, Batty’s spatial entropy method was used to assess the diversity index. The study results are comparable to understanding the relative spatial growth and patterns among the select urban centres across the zones. Like many Class–II cities, Tiruchirappalli Municipality Corporation has mostly recorded inward developments during the periods from 1996 to 2008; while from 2008 to 2020 they have recorded outward fringe developments leading to expansion of the city.