A catchment scale Integrated Flood Resilience Index to support decision making in urban flood control design

Urban floods are becoming a great concern of growing cities. Urban growth pressed by poverty and social drivers, together with possible climate change, may pose difficult challenges and increasing risk to safety and urban livability. In the face of this growing risk, urban drainage management is being pressed to move towards a flood risk management approach and that builds city resilience, or the capacity to continue functioning even in future hazardous conditions. In this context, this study proposes the development of an integrated Flood Resilience Index, departing from mathematical modelling tools and flood risk concepts. The Flood Resilience Index was built to support decision-making process in choosing design alternatives that improve flood control responses in future scenarios that surpass design standards. This way, flood control design decisions would be made under a quantitative assessment of the performance of a design alternative on potential flooding events in the long term. Flood Resilience Index was successfully tested in a watershed in the metropolitan region of Rio de Janeiro/Brazil where there is uncontrolled urban growth. It identified the best alternative to be a combined approach including sustainable urban drainage measures with river restoration techniques. When looking to the city centre area, this alternative scored a Flood Resilience Index of 47 over 100 against a conservative alternative of a dam, which only scored 20.