Efficiency of Nature-Based Solutions in North America: Participatory Research in ClimateCafé Vancouver and New Orleans

Effects of climate change in cities are evident and are expected to increase in the future, demanding adaptation. In order to share knowledge, raise awareness and build capacity on climate adaptation, “ClimateCafés” have been utilized since 2012 in over 50 global events. ClimateCafé is a field education concept involving different fields of science for capacity building in climate adaptation depending on the specific needs of stakeholders. This chapter describes the need, method and results of two ClimateCafés performed in North America in 2022. In North America, there was a clear demand for proof of the long-term efficiency of small-scale urban nature-based solutions (NbS), since the hydraulic capacity of rain gardens and swales is often questioned in low permeable soils and high groundwater tables. The main research question in the ClimateCafés is: Which variation of the (un)saturated infiltration capacity can be expected under conditions with low permeable soil and high groundwater tables (under sea level)? To answer this research question, participative monitoring of NbS has taken place on swales and rain gardens implemented in New Orleans (under sea level) and Vancouver (bed rock). The ClimateCafés aimed at generating context-specific data on nature-based solutions by using open-source tools and cost-effective data collection techniques. The results of the workshops show that relevant, multidisciplinary data can be gathered in a short period of time with limited resources. As example, over 500 individual NbS projects are mapped in both cities from which a selection is made for field research with several stakeholders. The method of the conducted research consisted of a full-scale testing method, measuring the long-term infiltration capacity of rain gardens and swales installed in the last two decades. The results show a high variation of empty times for rain gardens and swales (26–300 mm/h) with fast decreasing infiltration capacity after saturation of the soil (second test showed a decrease in the order of 35%). The ClimateCafés stimulated accelerated climate action and support for national and international knowledge exchange in adaptation solutions for a climate resilient future. Besides raising awareness and capacity building, the evaluation of the outcomes of the ClimateCafés Vancouver and New Orleans lead to practical guidelines and cost-effective interventions to optimize the performance of existing NbS and a strategy for implementing optimized NbS in the near future.