A global flood risk assessment has been performed to assess present and future flood risk in cities based on climate change and socio-economic devlopment. This study gives a rapid assessment to indicate where and to what extent cities are affected by river floods.
Global flood risk index for urbanized areas near rivers
Flooding is an increasing problem in cities everywhere around the world. Over the last 50 years global economic losses have significantly increased due flood related problems (Field et al., 2014; Stocker et al., 2013; UNISDR, 2013). In 2050 two-third of the world's population will live in urbanized deltas, which are vulnerable to flood disasters. A global rapid assessment is performed to indicate the severity and location of flood risk in cities for the present and the year 2030. This global approach, based on a single urban land cover class and one depth-damage function, is first compared to a European method based on five land use classes and five depth-damage functions. After which a global assessment is performed including two socio-economic development scenarios (SSP 2 and SSP 5) and two climate change scenarios (RCP 4.5 and RCP 8.5). The results of the Global and European methods have a high correlation of at least 0.97; however, absolute differences are substantial, in the order of billion euros. The effect of socio-economic development on flood risk is especially visible in parts of Asia, where a large increase in flood risk occurs compared to present day situation. The effect of climate change was less clearly spatially distributed and has an increasing or decreasing effect on flood risk depending on the location of the city. The combination of socio-economic development and climate change is seen as more realistic and shows an overall increase in flood risk especially in Indian and Chinese cities, directly related to socio-economic development. The use of indicators to make flood risk comparable between cities based on their size (km2) and number of residents resulted in a shift from more developed large cities to a ranking list dominated by Russian cities, with an increasing number of Indian cities when socio-economic development is implemented.