An index of Brazil’s vulnerability to expected increases in natural flash flooding and landslide disasters in the context of climate change

There is observational evidence that hydrometeorological extremes, such as heavy rainfall events, have become more frequent and intense in the last decades around the world. In Brazil, intense rainfall events that triggered flash floods and landslides were responsible for 74% of the deaths related to natural disasters in the 1991–2010 period. To evaluate Brazil’s hot spots of vulnerability to these disasters, two indices were developed using three data sets: (1) climate, with IPCC climate extreme indices; (2) environmental, including land use, drainage systems, relief, slope, road density and hydrography; and (3) socioeconomic, including the Gini coefficient, Human Development Index, housing conditions and a poverty-related index. Simulations at high resolution were carried out using the Eta 20-km regional climate model nested within two global climate models: HadGEM2 ES and MIROC 5 IPCC AR5 models. For the baseline period of 1961–1990, the vulnerability indices were adjusted by means of an iterative process and were validated by comparing them to the Brazilian National Disasters Data. The two indices were also used to estimate the vulnerability up to the end of the twenty-first century, using the representative concentration pathways (RCP) 4.5 and 8.5 from the IPCC AR5 RCP scenarios. The results indicate a large increase in Brazil’s vulnerability to landslides and flash floods in the context of climate change.