Global-scale river flood vulnerability in the last 50 years.

Masahiro Tanoue,Yukiko Hirabayashi,Hiroaki Ikeuchi

doi:10.1038/srep36021

Masahiro Tanoue, Yukiko Hirabayashi + Show 1 more

Open Access

https://doi.org/10.1038/srep36021

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Journal: Scientific Reports	Publication Date: Oct 26, 2016
Citations: 234	License type: CC BY 4.0

Affiliation: The University of Tokyo

Abstract

The impacts of flooding are expected to rise due to population increases, economic growth and climate change. Hence, understanding the physical and spatiotemporal characteristics of risk drivers (hazard, exposure and vulnerability) is required to develop effective flood mitigation measures. Here, the long-term trend in flood vulnerability was analysed globally, calculated from the ratio of the reported flood loss or damage to the modelled flood exposure using a global river and inundation model. A previous study showed decreasing global flood vulnerability over a shorter period using different disaster data. The long-term analysis demonstrated for the first time that flood vulnerability to economic losses in upper-middle, lower-middle and low-income countries shows an inverted U-shape, as a result of the balance between economic growth and various historical socioeconomic efforts to reduce damage, leading to non-significant upward or downward trends. We also show that the flood-exposed population is affected by historical changes in population distribution, with changes in flood vulnerability of up to 48.9%. Both increasing and decreasing trends in flood vulnerability were observed in different countries, implying that population growth scenarios considering spatial distribution changes could affect flood risk projections.

Highlights

Historical spatiotemporal patterns of vulnerability using a quantification model at a national scale[19,20,21]; these methodologies are applicable only to local scales due to limited data availability[22]
In accordance with a previous study, global mortality rates and global loss rates showed a decreasing trend (Fig. 2), and inverse relationships were found between flood vulnerability and GDP per capita (Fig. 3), indicating an improvement in flood vulnerability at the global scale since 1960 associated with economic growth
A significant negative trend in global mortality rate was seen across the whole analysis period (1960–2013), the rate for the most recent period (1990–2010) did not show a statistically significant trend (Supplementary Table S1)

Summary

Introduction

Historical spatiotemporal patterns of vulnerability using a quantification model at a national scale[19,20,21]; these methodologies are applicable only to local scales due to limited data availability[22]. One recent study[10] (hereafter referred to as J15) proposed a method to calculate flood vulnerability at the global scale in terms of the ratio of the reported flood loss and damage to the modelled flood exposure, obtained by using a global river and inundation model without considering any flood mitigation measures. Using this concept, historical improvements in flood vulnerability between 1990 and 2010 were successfully presented. We analyse the effect of historical changes in the spatial distribution of populations on flood exposure and vulnerability, because, even though several studies have identified both increasing flood exposures due to unplanned human settlements in flood-prone regions[29,30] and decreasing flood exposures as a result of autonomous adaptations (such as land use regulation and displacement of people to safer regions31), no study has yet quantified the temporal distribution or magnitude of these effects

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