Water is one of the most controversial natural resources one can think of, especially when debating on climate change and possible ways of transformation. Contrary, in urban areas, water is nowadays mainly invisible, tamed and expelled to the underground, although many scholars discuss its urgent necessity in today's cities' landscapes. This presentation gives an insight in the conflicting area between visibility and invisibility of water in a micro-scale field from a socio-cultural perspective. The research focus lays on different perspectives on every-day water practices, self-biographies around water and institutional arrangements in the field of water adaptation in a region with great risks of flooding. Through a large-scale workshop and interview series with inhabitants and stakeholders of Hamburg Lohbrügge, data was collected and analysed. The results are presented in a Lohbrügge map, as well as a complex model that gives an insight into new water trends. As a new approach in the socio-cultural field of water reserach in urban areas, a co-creative and visual attempt was made to demonstrate how cross-over participation can benefit both, the scientific work and every-day practices in urban institutions. Thus, an urgent call is made for more transdisciplinary and co-creation bottom-up research to tackle today's challanges in climate research, as well as institutional work in urban areas.

How to cite: Meier, L.: (In-)visibilities of water spaces in the urban sphere: a co-creative approach to explore (possible) adaptation strategies for Hamburg Lohbrügge, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-121, https://doi.org/10.5194/icuc12-121, 2025.

The "Hamburg Pluvial Flood Risk Map" aims to improve our understanding of the drivers, dynamics and interactions of climate-induced risks in Hamburg. Following the risk framework of the IPCC, we calculate a risk index based on hazard, exposure and (social) vulnerability. In this sense, we combine data from the previously published Social Vulnerability Index (von Szombathely et al., 2023) with novel meter-scale hydraulic simulations of urban flooding provided by the heavy rain hazard map of the city of Hamburg (BKG/FHH 2023), developing an integrated urban pluvial flood risk assessment. 

We enhance the modeling of social vulnerability by applying the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and the Shannon Entropy procedure. We propose high-resolution exposure modeling for residents affected by urban flooding, with two distinct exposure layers influencing well-being on the one hand and restricting mobility and accessibility on the other. We show that fundamentally new spatial patterns emerge for integrated pluvial flood risk in Hamburg, which differ from familiar socio-economic urban structures and at the same time differ clearly from a pure representation of the hazard. Presented through high-resolution spatial maps, this analysis aids in identifying adaptation needs and potential for sustainable transformation in urban areas and in prioritizing policy measures for climate change adaptation. 

How to cite: von Szombathely, M., Behrens, J., Hanf, F. S., Lennartz, M., Poschlod, B., Vogelbacher, A., and Sillmann, J.: Hamburg Pluvial Flood Risk Map, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-852, https://doi.org/10.5194/icuc12-852, 2025.

Urbanisation has a significant impact on the hydrological cycle, primarily through the replacement of natural, permeable surfaces with impermeable, constructed materials. This rapid increase in imperviousness, coupled with ongoing changes in precipitation patterns, has led to both an increased frequency and severity of urban flooding, especially in densely populated areas with limited green spaces. Residential gardens account for a significant proportion of a city’s total urban green spaces. These gardens can offer a promising opportunity for integrating nature-based solutions (NBS) to mitigate urban flooding by enhancing infiltration and reducing surface runoff. Therefore, this study evaluates the role of domestic gardens as NBS for flood mitigation within the highly urbanised Drimnagh neighbourhood in Dublin, Ireland. In particular, we consider diverse vegetation types, permeable and impermeable yard surfaces, and roof structures to assess their effects on flood dynamics during an extreme rainfall event on June 20, 2023. The neighbourhood covers an area of 69 hectares with 260 residential buildings. Using a hydrodynamic model, we simulate inundation depths, streamflow, runoff, and infiltration under four different scenarios for the same neighbourhood during this storm. Our results show that the best-case scenario, with improved garden vegetation and green roofs, could facilitate up to 1650 m³ of water infiltration water compared to the worst-case scenario, where all surfaces are paved. This scenarios with improved permeable surfaces can also reduce flood extents (up to 30%), mean inundation depths (8.3%), and flood peaks (5.6%) in the neighbourhood. This analysis highlights the potential of NBS implementation in domestic gardens in building urban flood resilience.

How to cite: Khan, S., Gholamnia, M., O’Loughlin, F., and Sajadi, P.: Role of Nature-Based Solutions in Mitigating Urban Flooding: A Case Study of Driminagh Neighbourhood in Dublin, Ireland, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-441, https://doi.org/10.5194/icuc12-441, 2025.

Climate change and its effects on water availability call for innovative and sustainable solutions for tackling water scarcity and drought in arid and semi-arid regions. Arid regions, grappling with the complex interplay of climate change, population growth, and heightened demand for water resources, demand a paradigm shift in the way we approach water management.

The island of Syros and the Cyclades region, in general, are historically affected by drought and water scarcity. To tackle these phenomena, the local communities have been dependent on alternative water resources, mainly rainwater harvesting and seawater desalination. Over the past years, managed aquifer recharge from reclaimed wastewater is also tested and implemented to increase the water safety of the island. The performance of a rainwater harvesting (RWH) system depends on various factors such as the amount of rainfall, the size and design of the system, the quality of the water collected, and the demand for water. Although RWH is embedded to the local architecture (flat roofs and built-in water reservoirs), not all buildings have the capacity to collect the maximum water for precipitation. These buildings represent all public buildings and buildings with limited storing capacity. Adding these buildings to the equation, the local community is closer to the RWH potential of 50 m³/capita per annum. Such communal rainwater application will reduce the demand on desalinated water production, especially outside the touristic period, resulting on decreasing energy needs and consequently CO₂ emissions. 

This work explores a visionary approach to addressing the water crisis in arid islands, advocating for the design of a communal rainwater harvesting administration and implementation framework tailored to the unique needs of arid and semi-arid islands. Such application will increase the water safety of these areas, while decreasing the environmental impact of energy demanding alternative water resources.

How to cite: Zarikos, I., Politi, N., Vlachogiannis, D., Sfetsos, A., and Vakondios, D.:  Communal rainwater harvesting framework for reducing water scarcity and desalinated water production in arid and semi-arid islands., 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-668, https://doi.org/10.5194/icuc12-668, 2025.

In recent years, weather-related extreme events have shown the limits of technical approaches to urban water challenges and highlighted the urgent need to rethink the relationship between cities and water and to see water as a partner in shaping transformative, climate-safe and just urban futures. However, existing scientific studies depicting future trajectories of urban water management have struggled to make the intertwined social and ecological dynamics of (transformative) urban adaptation tangible and accessible. This study focuses on the potential of visual communication of scenarios to stimulate both learning among scientists (during the process of creating the scenarios) and social learning (as a next step using the developed “narrative images”) to motivate diverse societal actors to engage with the complexity of sustainable urban water management. Art can overcome barriers of scientific and technical concepts and touch peoples' inner motivation for preserving and sustainably transforming our cities in a way that written texts cannot.

As sustainability challenges transcend disciplines, this study draws methodically on an interdisciplinary scenario approach. Three adaptation scenarios were developed in a participatory process and professionally visualized as “narrative images” using the city of Hamburg as a case study. The scenarios take place in 2050 depicting a gradient ranging from coping to incremental adaptation to transformative adaptation for managing the water-adaptation nexus: “Water defensive city,” “Water resilient city,” and “Water aware city.” The scenario study shows innovatively how to bring the humanities, natural and engineering sciences into a deliberative dialog, while at the same time promoting collective learning. It can serve as a model for successful future interdisciplinary research and scenario developing exercises.

How to cite: Hanf, F. S., Meier, L., Hawxwell, T., Oßenbrügge, J., Knieling, J., and Sillmann, J.: (Transformative) adaptation scenarios for dealing with urban water risks in Hamburg, Germany - Art as a tangible approach to complex socio-ecological relationships, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-666, https://doi.org/10.5194/icuc12-666, 2025.

Cities are increasingly recognized for their vulnerability to climate hazards and their pivotal role in achieving climate ambitions and sustainable development goals. Despite the growing interest in Climate Resilient Development Pathways (CRDP) as a framework to integrate climate action and development trajectories, the concept has yet to be operationalized for urban planning. Drawing on lessons from joint climate action in European cities and adaptive policy pathways planning, this research proposes three essential building blocks for CRDP planning in cities: (1) identifying and evaluating interactions between adaptation, mitigation, and sustainable development, (2) addressing time and uncertainty in planning, and (3) providing specialized information for CRDP. These building blocks were further developed into a structured framework for designing CRDPs and piloted in Cork, Ireland. The city of Cork currently faces joint challenges from increasing fluvial, pluvial and coastal flooding, as well as rapid growth and a commitment to achieve net-zero greenhouse gas emissions by 2030.

In this presentation, we will summarize the state of integrated climate action in European cities and the lessons for CRDP planning that inform our building blocks. We will also introduce the CRDP planning framework and illustrate its application in Cork, highlighting how synergies and co-benefits, as well as trade-offs are identified over time.

CRDP aims to achieve transformational change. The CRDP framework operationalizes this concept into a structured approach to move from siloed planning to comprehensive and integrated pathways for adaptation, mitigation and sustainable development for all.

How to cite: McEvoy, S., Langendijk, G., and Haasnoot, M.: Operationalizing Climate Resilient Development Pathways - a planning framework and its application in Cork, Ireland, 12th International Conference on Urban Climate, Rotterdam, The Netherlands, 7–11 Jul 2025, ICUC12-901, https://doi.org/10.5194/icuc12-901, 2025.