The importance of governance rearrangements (reassignment of positions, roles, and responsibility among actors in governance processes) and their implications on flood risk management has gained currency in evaluative environmental governance literature. However, much work has concentrated on building and applying frameworks to evaluate impacts of decentralisation, such that frameworks to evaluate impacts of recentralisation are still lacking. This paper uses the case of Bwaise III informal settlement in Kampala, Uganda, to assess the impacts of local government rearrangements on flood mitigation. We adapted a Water Governance Assessment Framework and conducted 22 in‐depth interviews with stakeholders, searched documentary sources, and carried out transect walks. We generated qualitative data on stakeholder experiences and perceptions regarding governance quality and flood mitigation prereform and postreform. The data were analysed using thematic content analysis to produce a scoreboard measuring changes in governance dimensions against progress in flood mitigation. In a follow‐up survey, 24 structured interviews were conducted to validate the data. Results show that the rearrangements led to time and cost savings, increased revenue, and sped up the implementation of flood management strategies and measures. The findings can be useful to policymakers at the interface of governance and flood management.