This extreme rainfall event occurred at Zhengzhou on 20 July 2021 is widely concerned, as it caused tremendous losses of both lives and properties. However, the evolution of areal rainfall is still not clear. In this study, Kdp observations were used for quantitatively estimating areal rainfall accumulation. Different estimation methods as well as QPE results were compared. We found that the selection of kdp estimation method has minimal impact on hourly rainfall accumulation.

We used a two-step approach with limited sampling effort in existing storm water infrastructure to illustrate the risk of biocide emission in a 2 ha urban area 13 years after construction had ended. First samples at a swale confirmed the overall relevance of biocide pollution. Then we identified sources where biocides were used for film protection and pathways where transformation products were formed. Our results suggest that biocide pollution is a also continuous risk in aging urban areas.

Surface water velocities are key in the calibration of physically based urban drainage models, but the shallow depths developed during non-extreme rainfall and the risks during floods limit the availability of this type of data. This study proves the potential of different imaging velocimetry techniques to measure water runoff velocities in urban catchments during rain events, highlighting the importance of considering rain properties to interpret and assess the results obtained.

We studied water partitioning under urban grassland, shrub and trees during a warm and dry growing season in Berlin, Germany. Soil evaporation was highest under grass, but total green water fluxes and turnover time of soil water were greater under trees. Lowest evapotranspiration losses under shrub indicate potential higher drought resilience. Knowledge of water partitioning and requirements of urban green will be essential for better adaptive management of urban water and irrigation strategies.