Evaluation of bioswale efficiency in consideration of climate and design features: A case study in Hong Kong

Sustainable drainage systems (SuDSs) have been increasingly implemented to mitigate the stress of urbanisation, climate change, and water scarcity. However, SuDS construction in densely populated metropolitan cities with a subtropical monsoon climate such as that of Hong Kong may encounter challenging field conditions and site constraints. This field scale study aimed to verify the performance of bioswale for flood resilience and water quality improvement under various simulated rainfall scenarios with different intermittency and intensity. In the six simulated rainfall events, the results showed that metal removal and flow attenuation were excellent under minor and moderate rainfall events, while the system performance was compromised during intensive rainfall events. The removal of turbidity and nutrients from the runoff was moderate owing to the low contaminant levels in the synthetic stormwater. The dry state of soil media led to more fluctuating results for water quality control. To further enhance the treatment capability under practical site constraints, the addition of appropriate soil amendments and the integrated use of different SuDS measures are recommended in order to achieve sustainable development goals and resilient water management.