## 1 Introduction
Extreme weather events, in particular, can significantly affect well-being, triggering high levels of stress, feelings of peril, and health issues. These impacts are particularly pronounced in urban areas [61; 62]. Despite the numerous efforts to prevent and alleviate the repercussions of climate change on urban infrastructure, there remains a gap in addressing how to support residents in coping with the mental health challenges that heighten their vulnerability [63]. Cities play a crucial role in addressing climate change, as they account for a significant portion of global energy consumption and greenhouse gas emissions, with 60% to 80% of energy usage and 75% of CO2 emissions originating from urban areas worldwide [64], cities have been proactive in monitoring emissions and enacting plans to minimise their environmental impact, often integrating sustainable development principles into their urban planning strategies [65]. However, it is imperative to highlight a concerning finding from a report by CDP [66], revealing that only 16% of cities are currently planning green spaces to mitigate climate change and promote biodiversity. Moreover, a mere 14% of cities have established crisis-management strategies, including early warning systems and evacuation protocols. The statistics mentioned underscore the critical need to ramp up efforts in bolstering green infrastructure and enhancing emergency preparedness in cities. Furthermore, positioning cities as pivotal partners for governments in advancing global climate objectives is crucial. Various initiatives, such as the UN Environment Assembly, are instrumental in addressing this imperative. Moreover, organisations like the Coalition for High Ambition Multi-Level Partnerships (CHAMP) are dedicated to fostering close collaboration between governments and cities, states, regions, and other subnational entities in climate action strategies. Additionally, groups like the C40 Cities Climate Leadership Group and the Global Covenant of Mayors play essential roles in supporting cities worldwide in their climate initiatives and sustainability efforts. In Poland, where the City with Climate project was conducted numerous national and international projects are being undertaken to help cities mitigate the impacts of climate change. Among these initiatives is the development of manuals to guide cities in adapting to climate challenges, offering valuable frameworks for preparing municipal adaptation plans [67; 68]. This study focuses on the outcomes of the City with Climate project, which ran from 2020 to 2023. The project aimed to improve the quality of life for residents while supporting cities in their pro-climate transition. Its impact was assessed across five key areas: air quality, urban green spaces, zero-emission transport, energy transition, and urban retention. For each area, a two-stage analysis was conducted that included a detailed diagnosis as part of a strategic consulting process, along with the development of road maps to guide the transition toward climate resilience and urban neutrality. This study focuses on a methodology for diagnosing urban areas to identify challenges in rainwater management and pinpoint intervention sites, such as local undrained depressions, to improve retention through nature-based solutions or infrastructural projects. The objectives of this study are as follows: to develop a methodology for identifying the most vulnerable areas within cities concerning flooding and urban retention; to test this methodology in collaboration with city authorities and stakeholders across different cities; to ensure easy reproducibility through the use of free data and open-source tools; and to present the results as a foundation for further actions, such as the planning of nature-based solutions or the reinforcement or modernisation of existing flood protection infrastructure. Consequently, this paper specifically elaborates on the diagnosis of urban retention.