In this chapter a science-based approach for planning land use is explored for the metropolitan region of Kampala (Uganda), in particular with regard to flood risk mitigation. A scenario-based planning approach was implemented to assess the impact of building densification of central locations on the overall pattern of urban growth and on flood risk of the city’s Upper Lubigi sub-catchment. Two spatially explicit models, a cellular automata model of urban growth and a rainfall-runoff flooding model, were used to project scenarios of landscape change to 2025 and assess their impact on flooding. Based on the simulations generated, we discuss in this chapter the limits of regional building densification in relation to flood risk. The results of our study suggest that densification policies must be implemented together with growth controls and greening policies, otherwise the impact of building densification on flooding is likely to range from (at best) negligible to considerably negative.