A novel model for simulating urban expansion under compactness scenarios on a regional scale

Urban expansion has a significant impact on sustainable development in rapidly urbanizing areas. The changes in population density and spatial compactness during rapid urban expansion significantly impact sustainable development. However, current regional-scale urban simulation models are rarely incorporated into population density and spatial compactness. This study proposes an ANN-based method for predicting future population density in a region. A spatial simulation model for urban expansion that takes into account the population density and urban spatial compactness (UECS model) is proposed. The model integrates top-down compactness control with bottom-up spatial allocation mechanisms using a novel roulette approach. The top-down control, which involves setting the future population density and average proximity expansion index (APEI), exerts a macro-level influence on spatial compactness. In contrast, bottom-up CA and cell proximity expansion index (CPEI) change the spatial compactness in urban expansion at the micro level. The validation using Western Africa as the study area shows that the UECS model has good simulation performance and strong control of compactness. Finally, based on the UECS model, we simulate urban growth in Western Africa from 2020 to 2060 under five different compactness scenarios at a 300-m resolution. The result suggests that future urban expansion in Western Africa will vary significantly under different compactness scenarios. The proposed model provides a framework for simulating different levels of urban compactness, which enables us to explore the impacts of different strategies on urban development and sustainability and provides the basis for urban development decision support.