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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Wenqing Liu

The Role of Sustainable Drainage Systems in Mitigating Urban Waterlogging Problems in China A Case Study of the Application of SuDS Practices in a residential community of Nanjing

Urban flooding is of great concern in low- and middle-income developing
countries in recent decades. Under the background of global urbanisation and
climate change, urban waterlogging has become a major water issue restricting
the economic and societal development in most cities of China. Since ‘grey
infrastructures’ in cities cannot fully alleviate the flooding pressure from extreme
precipitation anymore, a more resilient and reliable stormwater management
called ‘Sustainable Urban Drainage Systems’ is urgently needed and should be
properly implemented.

To explore the role of SuDS in mitigating urban waterlogging problems in China,
in this study, a ‘Casual Loop Diagram’ was generated to reflect underlying
causes of urban flooding in China. Besides, ‘Soil Conservation Service’ Curve
Number (SCS-CN) model was employed to evaluate the performance of nine
SuDS practices as retrofitting technologies in a residential community under
twenty-five designed scenarios.

The results indicated that urbanisation and climate change are two major
causes of severe urban flooding in China’s cities. In addition, the results from
the case study revealed that all nine SuDS practices are effective for urban
stormwater management. The implementation of designed soakaways,
rainwater harvesting systems and permeable pavements in the study area can
result in runoff reduction by 2.8-16.9% at different rainfall frequencies.
Moreover, swales and detention basins show exceedingly high costeffectiveness,
whereas green roofs, permeable pavements and rainwater
harvesting systems are less economically effective in terms of urban flooding