An assessment of Compound Flooding Impacts across the East Coast, USA

Understanding variability in flood damages and the underlying mechanisms is critical for predicting future changes to increase flood resilience. Increasing compound events have the potential to cause tremendous damage and losses, especially along coastal areas. However, the impacts of compound flood are still overlooked in disaster risk science, where a predominant focus still remains on single hazard analysis. In this study, a detailed assessment of flood damages from 2009 to present (13 years) is conducted, over East Coast, USA, based on the National Flood Insurance Program (NFIP) insurance claims records and historical storm events that occurred during the corresponding period. We applied an approach to physically identify areas potentially impacted by surge dominated, rainfall-runoff dominated, or compound events. Further, we link these areas with historical reports of flooding or storm losses. We demonstrated the actual impacts of major events, e.g., Irene (2011) and Sandy (2012), to analyze the differences in the corresponding claims data by detecting the underlying flood drivers. Up to date, the claim records have been investigated based on individual drivers, for example flood caused either by excessive river flow or by coastal flooding. Hence, it is crucial to assess how does compound flooding reflect on insurance flood claim records. The results obtained in this study demonstrate the potential of integrating a flood type-specific mapping system into a compound flood impact estimation, for improving flood risk estimation. The outcome of this study will be helpful for the coastal communities to better understand their risk to the compounding impacts of various environmental forcings (heavy precipitation, surge and the effect of sea level rise), which is important for increasing their resilience to future compound flooding events.