Storylines of Hurricane Sandy under climate change to assess compound coastal flooding impacts in New York City

While high impact weather events pose considerable challenges to society, we have limited understanding of their risks and potential impacts due to their rare nature. Climate change, in combination with internal climate variability, increases the uncertainty around these events and their impacts in the future. Storylines offer a non-probabilistic approach into estimating and understanding such events and their impacts conditioned on specific assumptions and scenarios, such as climate change and internal climate variability. Our study presents storylines of Hurricane Sandy (2012) to assess compound coastal flooding's impact on New York City's critical infrastructure under different scenarios. These include the effects of climate change, such as changes in storm dynamics and sea-level rise, as well as internal climate variability, accounting for variations in storm intensity and location. We use a comprehensive modelling framework, spanning from the driving climatological conditions to compound flooding and societal impacts. Our findings indicate that a 1m sea level rise could increase flood volumes by an average of 4.2 times, while internal climate variability could lead to a 2.5-fold increase in flood volumes. We find that impacts on critical infrastructure depend not only on flood volume, but also on the predominant flood hazard in each storyline, like storm surge or local precipitation. This study highlights the importance of developing societal-relevant scenarios that consider both climate change and internal variability. Such scenarios, coupled with a comprehensive modelling framework, provide useful information for decision making when preparing for high impact events in the future.