Cities have a distinct different weather and climate than the countryside, best known as the urban heat island effect which can have negative effects on the human health, labour productivity, and energy demand. In addition, cities are vulnerable to flooding after peak-showers, and are major sources of greenhouse gasses. This presentation is a journey along five years of field observations in Amsterdam Atmospheric Monitoring Supersite which contains 24 weather stations across Amsterdam and a research tower measuring solar and thermal radiation, evapotranspiration (by eddy covariance and scintillometer) and carbon dioxide fluxes. These observations are complemented by traverse (bicycle) heatstress observations, sodar and balloon sounding observations during hot summer days. Results show neighborhoods in Amsterdam have their characteristic temperature dynamics, with high temperatures in the relatively open neighborhoods during the day, and relatively high temperatures in the city center at night. In addition, a climatology of rainfall radar observations reveal an enhanced precipitation in Amsterdam with respect to its surroundings. Also, we learnt the mobility restrictions due to the covid-19 pandemic lowered the city’s CO2 emission by 40%. Moreover we show results from hectometer-scale numerical weather prediction model results for Amsterdam, which can be used as instrument to study Amsterdam’s forthcoming climate and contribute to its sustainable future.

The amount and dynamics of urban water storage play an important role in mitigating urban flooding and heat. The storage capacity serves on one hand as a buffer to prevent flooding during heavy rainfall. On the other hand, in absence of rain, it provides the water needed for evaporation to cool the city preventing heat stress. Assessment of the capacity of cities to store water remains challenging due to the extreme heterogeneity of the urban surface. The way the storage gradually empties during dry periods, can provide insight on the water storage capacity of urban surfaces. Assuming evaporation is the only outgoing flux, the water storage capacity can be estimated based on the timescale and intercept of its recession. In this paper, we test the proposed approach to estimate the water storage capacity at neighborhood scale with latent heat flux data collected by eddy covariance flux towers in twelve contrasting urban sites with different local climate zones, vegetation cover and characteristics and background climates (Amsterdam, Arnhem, Basel, Berlin, Helsinki, Herakleion, Łódź, Melbourne, Mexico City, Seoul, Singapore, Vancouver). Water storage capacities ranging between 1 and 28 mm were found. Additionally, the amount of stored water and the related evaporation halve every 1.5 to 7 days. According to our results, urban water storage capacity is at least five times smaller and evaporation decreases at least five times faster than what is found in natural forests and grassland.

How to overcome urban flooding and drought caused by extreme and volatile precipitation through innovative forms of climate adaptation? And how to fit this into a heavily occupied public urban space? Challenging questions that, in light of climate change and the continuous process of rapid world-wide urbanization, become more and more critical to those involved in urban water management and resilient urban design. Amsterdam, amongst others, faces an enormous challenge to protect itself against the consequences of extreme weather due to a changing climate. Infiltration and buffering of rainwater in the underground can prevent potential problems related to flooding and drought while the burden on the urban water system is minimized. Space in the underground is scarce, however. Critical infrastructure and urban greening compete with climate adaptation measures for the limited space available. Smart integral designs with an eye for linking opportunities, function combinations, and the need for urban transition, are necessary to deal with the underground in a sustainable manner. Roads offer a promising opportunity to realize underground water buffers in urban areas in a spatially efficient and sustainable manner. Now that various Dutch municipalities are experimenting with various forms of underground water buffers in roads, it turns out – however- that professionals are struggling to make the right choices due to a lack of insight and practical examples. Knowledge on the stability, (cost) effectiveness, sustainability, contribution to flood and drought control, potential for use within the heavily occupied urban underground, and urban scalability and transferability is missing here. Through practice-oriented research, the project ‘Roads as urban water buffers’ (2021-2023) provides insight into how water buffering roads (can) function in practice. Through field-research in various Dutch cities and municipalities we study, first of all, the stability, hydraulic and hydrological functioning, and sustainability of water buffering roads. Through MKBA-analyses we quantify, secondly, the cost-effectiveness. Through focus group discussions we identify, thirdly, the possibilities and obstacles with regards to the process of design, implementation, management and maintenance, as well as scalability and transferability of design and practice. Through GIS-analyses we develop, finally, an Opportunities-Atlas showcasing the potential for roads as urban water buffers in urbanized contexts. Within this presentation we share some of our first results and discuss ways forward.