Résumé : Worldwide, conventional stormwater management policies and practices are under pressure due to the mal- functioning of existing urban drainage systems, population growth, urbanisation and climate change. In response to these developments, we have seen an increase in the development and uptake of alternative actions. These actions often involve physical infrastructure moving from the underground to the surface and an increase of stakeholder interactions and involvement. We draw upon the literature on transitions of socio-technical systems to understand these changes in stormwater management policies and practices in the case of a local municipality in Brussels, Belgium. Building upon previous research by Rijke et al. (2013), we assert that every transition stage (early, middle, late) can be linked to typical activities. We particularly aim to understand how a transition process is influenced by technical attributes of actions, i.e. whether they are soft, green or grey, and by gov- ernance configurations, i.e. whether actions are more centralised or decentralised and more formal or informal. In doing so, we looked into the development, implementation as well as the diffusion of alternative actions. Our results show that in the early stage of transition, soft actions, such as manuals, legislation and economic in- centives, prevail. In the diffusion of actions, decentralised processes and collaboration between formal institu- tions and informal networks play a key role. We further found that attention should be given to preventing the alienation of civil society during diffusion processes.