Modelling spatial–temporal expansion of Lilongwe City using Shannon’s entropy model through semi-dynamic environmental mapping and analysis

Abstract

This study involves analysis of the urban spatial–temporal expansion of Lilongwe City from 1973 to 2020 using Shannon’s entropy model through time-series satellite mapping. Landsat images from 1973 to 2020 in a nearly 10-year interval are used to determine spatial–temporal land use/cover changes. The city is zoned into 1 km concentric rings and four pie sections to determine both directional and spatial urban expansion trends while Shannon’s entropy model is employed to determine the degree of dispersity of the city’s sprawl. A linear regression model incorporating population as an explanatory variable is then applied to predict the spatial expansion trends for Lilongwe City. Results show that the built-up area in Lilongwe City expanded by 465.4% (9.9% per year) from 1973 to 2020, making it the second-largest land use/cover type in the city, after vegetation. Consequently, vegetation cover decreased by − 32.7% (− 0.7% per year) during the same period. High relative entropy indices (> 0.9) obtained from Shannon’s entropy model indicate a dispersed urban development for the city during the entire period of study. The North-West quadrant of the city has the highest proportion of urban expansion while the North-East quadrant has the lowest proportion, in a relative sense. Regression model predictions show that the city will most likely continue to expand by the year 2023 and then increase exponentially by the year 2033, due to high population growth. The results of this study will assist city authorities to control the expansion of the city and anticipate patterns for future urban sprawl.