Accounting public and individual flood protection measures in damage assessment: A novel approach for quantitative assessment of vulnerability and flood risk associated with local engineering adaptation options

A typical engineered flood protection for a community exposed to fluvial flooding is constructions of flood defense dedicated for public-wide protection. Over the past few years, there have been efforts to mainstreaming individual precautionary measures as to reduce risk of flooding. Consideration of individual protection measures alongside public protection measures is mainly to increase resistance of local communities to flood impacts whilst deliberating the spatial constraints of public protection measures and optimizing cost of adaptation. However, quantification of vulnerability and risk reduction of combined public and individual protection measures has not received much attention, far less a risk-based economic analysis. In assisting flood risk management decision making, a systematic approach to quantify vulnerability and flood risk of conditions with the combined protection measures is deemed crucial. This study proposes a methodology to assess vulnerability and flood risk of flooding considering combined public and individual protection measures, aiming for relevant applications in economic appraisal of local protection options. The applicability of the methodology is demonstrated using a case study of a residential area of Teddington near the Greater London. A range of different possible levels of protection was also included to exemplify the usefulness of the methodology in search for an optimal protection level. The results show that the combined public and individual protection can reduce flood risk significantly. The study highlights that the methodology can serve as a tool for a practical and manageable vulnerability and flood risk assessment.