The Taihu Basin is home to some of the most economically active and populous cities in China, including Shanghai. The Basin lies in the coastal delta of the Yangtze River and is defended from frequent flooding by a complex system of flood control infrastructure (including dikes, numerous large sluice gates and pumping stations). Flood risk in the Basin is closely related to the reliability of the flood defences. The information available to support system reliability analysis is however limited. A simplified defence classification and reliability analysis has therefore been adopted in which the behaviour of defence subsystems (dike rings) are presented through a single representative fragility curve. A combination of expert judgement and available quantified data is used to support the analysis. The approach is found to be informative within the context of (i) a broad scale flood risk analysis, (ii) an exploration of longer term management policies and (iii) targeting more detailed analysis and data collection required to support specific management choices.