Domestic gardens as rainwater testing grounds: understanding landowner motivations in co-constructing small-scale nature-based solutions in Brussels-Capital Region

Integrated Urban Stormwater Management (IUSM) is increasingly framed as a key approach to addressing urban water-related challenges such as flooding and drought. In the Brussels-Capital Region, the predominance of private residential parcels positions landowners as pivotal actors in advancing climate adaptation and sustainability policies. However, despite policy support, the implementation of IUSM on private land remains limited due to regulatory, morphological, and hydrogeological constraints. This paper draws on findings from the Urban Climate Change Experiment Ilot d’Eau Ensemble (2021–2024), which explores the co-production of IUSM through participatory design and construction processes. Domestic gardens are mobilised as testing grounds for landowner stewardship through the implementation of small-scale and context-specific Nature-based Solutions. Focusing on three cases, the paper examines landowners’ roles, motivations, and perceived benefits through the lens of public service co-production. Based on participatory observations and semi-structured interviews, the analysis shows that landowners’ roles, motivations, and perceived benefits co-evolve through participation, supporting a conceptualisation of philanthropic collective co-production as the aggregation of individual actions. It further highlights how Urban Climate Change Experiments enable processes of embedding, through which decentralised interventions incrementally contribute to systemic change. The findings also point to the emergence of necessity-driven motivations, while underlining the fragility of such processes and their dependence on institutional support.