Assessing current and future flood risk estimates associated with hurricane rainfall under the 1.5°C and 2°C Paris Agreement goals in Puerto Rico

Record-breaking hydrometeorological disasters such as Hurricane Maria in 2017 have once again highlighted the severe disaster risk exacerbated by a changing climate facing Caribbean small island states. Hurricane rainfall is a key cause of flooding in many Caribbean islands. Yet, despite the projected changes in hurricane rainfall under climate change and the attribution of a climate change signal in particular hurricane rainfall events, estimates of current and future flooding associated with hurricane rainfall are limited in the Caribbean. This research outlines a method for assessing current and future flood risk estimates in the Caribbean, producing an event-based pluvial model using hydrodynamic model LISFLOOD-FP to simulate flood hazard in Puerto Rico for present day, 1.5^oC and 2^oC Paris Agreement climate projections. An event set of 59,000 hurricane rainfall estimates from a synthetic hurricane rainfall model was applied as the rainfall input to the hydrodynamic model, simulated across time (2-hour timesteps) and space (0.1-degree spatial resolution). The event-based pluvial model was run at the island-scale in Puerto Rico (9104km²) at 20m and 90m resolution to produce event-based flood hazard estimates under present day, 1.5^oC and 2^oC climate change projections. The flood hazard event set was then combined with population data to get estimates of exposure exceedance under present day, 1.5^oC and 2^oC climate change projections. The results of this research will provide useful information for both the hydrology and disaster risk reduction communities regarding the potential changes in population exposure to hurricane rainfall-induced flood events in Puerto Rico, as well as how particular characteristics of hurricane rainfall affect flood hazard under 1.5^oC and 2^oC climate change. This research will also highlight how an event-based pluvial flood model can be utilised to assess a range of possible current and future flood scenarios, as well as how important different aspects of the modelling are for these small island studies. This information is crucial for both current and future disaster risk reduction and climate change adaptation planning in the Caribbean – an ever-increasingly urgent task.