Exploration of expansion patterns and prediction of urban growth for Colombo City, Sri Lanka

This study attempts to analyze and simulate urban growth pattern of Colombo city in Sri Lanka which is a dynamic and rapid urbanizing region. The spatiotemporal urban growth patterns during 1997–2019 were first analyzed by comparing Land Cover (LC) maps for time intervals between 1997–2008 and 2008–2019 using intensity and growth pattern analysis. Urban lands in Colombo have grown in a faster rate during 1997–2008 as compared to 2008–2019 period. The prominent spatial expansion pattern during 1997–2008 is outlying, as opposed to edge expansion which is predominant during 2008–2019. These major urban expansion patterns were modeled to predict the future urban structure of Colombo in 2030 using FUTURES (FUTure Urban-Regional Environment Simulation) model. FUTURES is a patch-based, multilevel modeling framework for simulating the emergence of landscape spatial structure in urbanizing regions. Simulated result generated from the model reveals substantial agreement with real ground urban changes showing a kappa value of 0.78. The model allows to predict three different scenarios, namely Business as Usual, Infill Growth and Sprawl showing over 100 km2 increase in urban lands by 2030. Predicted urban structure was then compared with proposed development plan. With certain limitations arising from available data, the model is effective in predicting possible urban scenarios and providing valuable inputs to support better decision making for sustainable development of Colombo city. The results demonstrated in this study would be useful in modelling urban growth in other cities and further validate the efficacy of the proposed workflow.