Dealing with hurricane surge flooding in a changing environment: part II: risk-based coastal adaptation design considering hazard-adaptation interactions
摘要
Climate change exacerbates tropical cyclones (TCs) induced flood risk that demands competent adaptations. Current studies often overlook hazard-adaptation interaction when designing adaptation measures and apply “bathtub” flood modeling method which may overestimate flood risk. Here, we propose the Inundation Modeling-based Overtopping Risk Analysis (IMORA), where we model coastal inundations considering interactions between storm tide hazard and adaptation measures (in this study, a floodwall system) with a physics-based but computationally feasible method. We apply IMORA to assess adaptation strategies for lower Manhattan, NYC. We used large numbers of synthetic TCs to drive a storm tide model (ADCIRC) and an inundation model (SFINCS) to obtain inundations and damages with different floodwall levels. We calculated expected annual damages (EADs) and expected total damages (ETDs) with different floodwall levels. Considering the effect of sea level rise and storm intensification, we estimated ETDs (2% discount factor) from 2025 to 2100 with no adaptation to be $1.11 billion and $1.75 billion under the moderate emissions scenario (SSP2-4.5) and the high emissions scenario (SSP5-8.5), respectively. We determined optimal floodwall elevations to be 18.25 feet and 20.25 feet with minimum net expected costs (ETD plus investment) of $36.7 million and $47.17 million under SSP2-4.5 and SSP5-8.5, respectively. The optimal level considering SSP2-4.5 is comparable to the design level proposed in USACE’s NYNJ-HATS coastal storm risk management for this region, although USACE’s analysis method is challenged. We find that assuming “bathtub” overestimates ETDs by up to 143% under SSP2-4.5 and 214% under SSP5-8.5 compared to applying the IMORA framework.