WATERUN project aims to develop an innovative methodology to contribute to the implementation of urban water runoff management plans in cities based on the Water-Sensitive Urban Design concept. This methodology will provide preventive and mitigation solutions and best management practices adopting a holistic perspective (from source identification to remediation strategies) for diffuse water pollution control in urban catchments. The target is to transform the urban water runoff management by the development of identification, planning and risk-based tools and new working procedures (guidance), counting on the early involvement of the main urban water management and governance actors (co-creation process) to ensure a wider and faster adoption. Three case studies (city of Santiago de Compostela, city of Aarhus and city of Amman) have been chosen to obtain data and to elaborate, perform and validate the proposed WATERUN methodology. These case studies have been selected according to different climate conditions, land use and level of implementation of measures for diffuse pollution, in order to validate the tools in different scenarios. Key stakeholders as RTO, industry, public authorities, urban planners and citizens will participate in a continuous co-creation process from a multi-disciplinary approach ensuring that decisions for urban water runoff management are made with complete comprehension of environmental, social and economic dimensions. In addition to providing solutions for sustainable urban water management, the WATERUN methodology will allow to gain advanced knowledge on diffuse water pollution in cities in a climate change context, thus contributing to protect water bodies and the environment, and ensuring high water quality for all.