This report outlines the Flood Delta City Index, which helps cities to better understand the dominant drivers of flood risk, formulate ambitions, and compare and share their results with other delta regions. The index aims to help decision makers in delta areas to select appropriate adaptation and mitigation strategies, by providing a clearer picture of the main sources of risk and how this risk evolves under changing conditions. The Flood Delta City Index is complementary to existing qualitative risk assessments and indices that are developed mainly within academia. These flood indices are often qualitative, time-intensive to produce and risk a problem of subjectivity. Also, many resilience-based or adaptability-based indices do not distinguish between quantitative (flood) risk and qualitative indicators, such as socio-economic data or governance aspects that may positive influence future risk, making it difficult to clearly assess and compare flood risk.