Sensitivity of sustainable urban drainage systems to precipitation events and malfunctions

In recent years, sustainable urban drainage systems (SUDSs) have become increasingly popular, sometimes taking over large parts of conventional stormwater management. SUDSs are usually designed using simple design procedures based on statistical rainfall data, without long-term simulations or real rainfall events. In addition, there is little experience of how SUDS respond to potential failures and malfunctions, often caused by ageing infrastructure and lack of asset management. Based on these two factors influencing the hydrological performance of SUDS, this study investigates the sensitivity of seven different SUDSs to rainfall events and malfunctions. The study was conducted using the SWMM 5.2 modeling software and the low impact development (LID) module was implemented for a period of 60 years. The SUDS are studied as individual infrastructure and as part of a small urban catchment. The results show that only the green roofs and rainwater cisterns have a statistically significant correlation between the length and return period of rain events and runoff values, with higher correlations for longer rain events. In contrast, the failures and malfunctions investigated can have a significant impact on the hydrological performance of SUDS. In particular, the design return period of SUDS was occasionally significantly exceeded for the strong malfunction scenarios studied.