The Pearl River Delta (PRD) region has experienced rapid economic and population growth in the last three decades. The delta includes coastal megacities, such as Hong Kong. These low-lying urbanised coastal regions in the PRD are vulnerable to flood risks from unpredictable climatic conditions. These can result in increasing storm surges, rising sea level and intensified rainstorms causing coastal and inland flooding, all of which impact the delta. This paper has taken the coastal megacity of Hong Kong as a case, focusing on two study sites: Shenzhen River and Tai O town, chosen for their peculiar inland and coastal flood problems. A sustainable flood risk appraisal (SFRA) template was developed against which sustainable flood risk management (FRM) practices in these sites were benchmarked. Thirty-eight stakeholders were interviewed during this research in order to understand the current FRM practices, their barriers and their constraints. It was found that FRM in the case study currently focuses on hard engineering, while neglecting other important sustainability indicators. A SFRA practice that takes public participation, equity of flood preparedness and environmental friendly into account could be effective in achieving sustainable flood risk mitigation practices in Hong Kong and other coastal cities in the PRD.