An Integrated Assessment of Urban Drainage System Performance and Risk in Built-Up Areas

Since the 1980s, alongside China's large-scale urban construction, urban stormwater and sewage drainage systems have also undergone rapid development. By the end of 2023, the total length of urban drainage pipelines in China reached 952,500 km, with over 5,000 urban sewage treatment plants in operation, and a total treatment capacity of 227 million cubic meters per day (Hongchen, 2025). However, the rapid development of urban drainage systems has gradually exposed serious issues, primarily in the following three areas: (1) The lack of proper planning and design for stormwater major drainage systems in urban development has led to an increasing risk of urban flooding; (2) illegal connection of stormwater and sewage pipes, the abnormal "combined sewer" system, and a lack of effective operation and maintenance management, leading to severe issues such as sedimentation and overflow risks; (3) low pollutant treatment efficiency in sewage systems. This paper uses the TK River Basin, China, as a case study, employing a comprehensive approach that combines continuous monitoring, a physics-based model, and a data-driven model to conduct an integrated assessment of performance and risk in the existing urban stormwater and sewage drainage systems, providing support for the renovation, upgrading, and operation and maintenance management of urban drainage system.