Effects of Climate Change on Exposure to Coastal Flooding in Latin America and the Caribbean

Abstract

This study considers and compares several of the most important factors contributing to coastal flooding in Latin American and the Caribbean (LAC) while accounting for the variations of these factors with location and time. The study assesses the populations, the land areas and the built capital exposed at present and at the middle and end of the 21st century for a set of scenarios that include both climatic and non-climatic drivers. Climatic drivers include global mean sea level, natural modes of climate variability such as El Niño, natural subsidence, and extreme sea levels resulting from the combination of projected local sea-level rise, storm surges and wave setup. Population is the only human-related driver accounted for in the future. Without adaptation, more than 4 million inhabitants will be exposed to flooding from relative sea-level rise by the end of the century, assuming the 8.5 W m-2 trajectory of the Representative Concentration Pathways (RCPs), or RCP8.5. However, the contributions from El Niño events substantially raise the threat in several Pacific-coast countries of the region and sooner than previously anticipated. At the tropical Pacific coastlines, the exposure by the mid-century for an event similar to El Niño 1998 would be comparable to that of the RCP4.5 relative sea-level rise by the end of the century. Furthermore, more than 7.5 million inhabitants, 42,600 km2 and built capital valued at 334 billion USD are currently situated at elevations below the 100-year extreme sea level. With sea levels rising and the population increasing, it is estimated that more than 9 million inhabitants will be exposed by the end of the century for either of the RCPs considered. The spatial distribution of exposure and the comparison of scenarios and timeframes can serve as a guide in future adaptation and risk reduction policies in the region.

Fig 1. Exposure of population to rSLR scenarios.

(a) Exposure levels for population projected to 2090 and rSLR for RCP4.5 (b) Difference between RCPs (c) Difference in exposure to the RCP4.5 sea levels for population projected in 2090 and reference levels (year 2011).

Fig 2. Exposure of land surface (upper panels) and Built Capital (lower panels) to rSLR scenarios.

(a) Exposure levels for land inundated by rSLR for RCP4.5 (b) Difference between RCPs for land inundated (c) Exposure levels for built capital inundated by rSLR for RCP4.5 (d) Difference between RCPs for land inundated.

Fig 3. Population exposed to El-Niño scenarios.

(a) Sea level induced by the El-Niño-1998 event with population in 2011 (b) Sea level induced by the El-Niño-1998 event at the mid-century, including rSLR (c) Difference of exposure between El-Niño-1998 by the mid-century and the SLR projection for RCP4.5 (d) Difference of exposure between El-Niño-1998 atop the rSLR projection for RCP4.5 and the rSLR projection alone. [N98]: El-Niño-1998 event induced mean sea level; [rSLRyy]: relative sea-level rise for year ‘yy’; [RCP4.5]: scenario of rSLR for the end of the century corresponding to the RCP4.5.

Fig 4. Flooding exposure from present 100-yr extreme sea level.

(a) Population; (b) land surface and (c) built capital at 2011 reference values.

Fig 5. Exposure of population and built capital to future rSLR and present 100-yr extreme sea level.

(a) Population exposed to RCP8.5 rSLR and present 100-yr extreme sea level; (b) difference of exposed population between RCPs (c) Built capital exposed to RCP8.5 rSLR and present 100-yr extreme sea level; (d) difference of built capital exposed between RCPs.