Building-level changes reveal ubiquitous intra-urban dynamics in Nairobi, Kenya

While spatial analysis has provided great insights into the expansion of built-up areas, changes within built-up areas have mostly been ignored. As a result, the amount of change within existing urban areas and the change processes they represent remain unknown. Even so, such changes can have important implications for urban sustainability. Here, we use very-high-resolution imagery to analyse different types of building-level changes in Nairobi, Kenya, between 2010 and 2021. Specifically, we manually map whether buildings appeared, persisted, changed, were replaced, or removed, and link these changes to urban development processes. We find that removal, replaced, and renewal combined make up as much as 29% of the total mapped building area in 2010. These changes highlight intricate patterns of urban change, driven by processes such as slum formalisation, rezoning and urban renewal. Our approach provides a generalisable framework for analysing urban change within built-up areas.