Quantitative assessment of inundation risks from physical contributors associated with future storm surges: a case study of Typhoon Maemi (2003)

Future storm-induced inundation risks were assessed by performing storm surge modeling based on Typhoon Maemi (2003) under the generic climate change scenarios proposed by IPCC AR5. The three physical factors governing the projected aggravation of inundation damage in a coastal basin (i.e., sea-level rise (SLR), direct runoff (DR) and tropical cyclones (TCs)) were defined and considered in the modeling both individually and in combination. With the application of a coupled hydrodynamic–hydrologic model, the inundation extent during the storm event under both current and year 2100 climate conditions was evaluated, and the impact of each factor on the inundation risk was identified. The intercomparison among the results revealed that SLR was the most influential single flooding driver aggravating the future inundation risk, and TC intensification was two-thirds as influential as SLR. However, DR was predicted to make a nearly negligible contribution and to have a minimal impact despite its significant projected increase in the future. Apart from the contributions of these three factors to aggravating the inundation level, the ways in which they affected the inundation risk were quite distinct. Additionally, the result considering both SLR and TC intensification demonstrated that nonlinear interactions between these factors can occur and further amplify the inundation damage. Finally, it was revealed that, depending on the level of the climate change projection, future storms with intensified rainfall and TC properties are likely to cause the maximum projected inundation damage in the study area to increase by up to 28.7% in inundation extent and by 236.6% in inundation volume relative to the current conditions without altering the spatial pattern of the inundation depth distribution.