Climate change is severely affecting all regions of the world, and urban water management has become a major urban challenge. Although nature-based solutions (NBSs) have been widely implemented in developed countries in the Global North to address stormwater-related challenges in urban areas, implementation of such approaches in Viet Nam and other Asian countries remains limited. In addition, comprehensive and critical reviews of NBS adoption and development processes in Viet Nam are scarce. This study aims to clarify several aspects through a literature-based review: to understand the development of urban water management in Europe and Asia (China and Southeast Asian countries) along with the drivers for NBS implementation in Viet Nam, to explain the barriers to NBS adoption in Viet Nam, to present feasible solutions for promoting NBS adoption, and to explore future perspectives for NBS development in the context of Viet Nam. Although significant barriers exist, opportunities for NBS implementation are evident. The findings of this study can be used to promote NBS in other municipalities in developing countries.

Owing to climate change, heavy rainfall events have increased in recent years, often resulting in urban flooding. Urban flood models usually consider buildings to be closed obstacles, which is not the case in reality. To address this research gap, an existing 1D/2D model was extended with underground structures. The underground structures were located using site visits, Google Earth, and information provided by the city administration. Control strategies were used to represent partially open doors or tilted windows. The model was simulated with three measured rainfall events in three different scenarios. Scenarios with underground structures resulted in small storage volumes in the structures and a slightly less flooded area on the surface. The assumptions made were analysed using sensitivity analysis. Varying the number and location of underground structures resulted in small variations in the stored volume and surface flood volume. The sensitivity analysis also showed that the thresholds for height and velocity had a large impact, whereas the opening percentage did not influence the number of buildings affected. The conclusion of the study is that the inclusion of underground structures has little effect on the predicted flooded areas but can be useful in quantifying the water depth in potentially vulnerable buildings.

In Alpine cities, water management needs to be adapted to the challenges of climate change, including altering temperature and precipitation patterns. Blue-green infrastructure (i.e., the combination of nature-based and technical solutions) can help to improve the water and energy balance, to increase the evaporative cooling effect, to maintain sufficient soil water availability and to reduce runoff peaks. Thus, it can reduce the risks of heat, drought and flooding, and improve the overall quality of life in cities. The implementation of blue-green infrastructure requires an interdisciplinary approach, as mechanisms of urban water management and ecohydrology (i.e., energy balance and soil-plant-atmosphere continuum) must be optimized with regard to the common goal.In the research project 'BlueGreenCities', ecological and technical disciplines are integrated to close knowledge gaps regarding (1) land-atmosphere interactions in ecological, hydrological and meteorological systems, and (2) the performance of blue-green adaptation measures under different climate scenarios in alpine urban areas. We present first results of measurement campaigns and eco-hydrological modelling to better understand the energy budget of various green spaces in the city of Innsbruck, Austria. Moreover, we give first insights if the specialty of the alpine setting (increasing summer droughts, but still cold winter temperatures) will be a chance or a burden for the current urban vegetation in the future.The outcomes of our project underpin the importance of climate-friendly and future-proof planning of urban green spaces to ensure proper functioning of the blue-green infrastructure concept. The results support scientists as well as urban planners, land developers and policy stakeholders in decision-making for sustainable and flexible water management systems that maintain human well-being, economic development and environmental protection. This work is funded by the Austrian Climate and Energy Fund in the project BlueGreenCities (Project No. KR21KB0K00001), funding period: October 2022 until September 2025.

Urban flooding is a growing global challenge, driven primarily by climate change and rapid urban development, which place increasing pressure on urban drainage networks. This study investigates the impacts of climate change and mitigation strategies in Innsbruck, Austria. Future periods are represented by design rainfall events scaled using climate change factors derived from bias-corrected convection-permitting simulations, while mitigation strategies are modelled by reducing the impervious connected area by 10, 20, and 30%. The results show climate change factors that indicate a strong intensification of short-duration, frequent rainfall and an increase by more than 31% in sewer surcharge and surface flooding under future conditions. Reducing the impervious connected area by 30% effectively counteracts the negative impacts of climate change in extreme events. However, the benefits of decoupling strategies are more pronounced for moderate precipitation events than for extreme ones and vary from 350 m3/ha surcharge reduction between districts. The analysis highlights that a spatially heterogeneous strategy is more effective, as decoupling is more effective in districts with high hydraulic pressure. These findings demonstrate a clear potential of decoupling measures to mitigate climate change impacts on urban drainage, but underscore the need for strategic implementation to maximize effectiveness.