The impacts of climate change on river flood risk at the global scale

Abstract

This paper presents an assessment of the implications of climate change for global river flood risk. It is based on the estimation of flood frequency relationships at a grid resolution of 0.5×0.5°, using a global hydrological model with climate scenarios derived from 21 climate models, together with projections of future population. Four indicators of the flood hazard are calculated; change in the magnitude and return period of flood peaks, flood-prone population and cropland exposed to substantial change in flood frequency, and a generalised measure of regional flood risk based on combining frequency curves with generic flood damage functions. Under one climate model, emissions and socioeconomic scenario (HadCM3 and SRES A1b), in 2050 the current 100-year flood would occur at least twice as frequently across 40 % of the globe, approximately 450 million flood-prone people and 430 thousand km 2 of flood-prone cropland would be exposed to a doubling of flood frequency, and global flood risk would increase by approximately 187 % over the risk in 2050 in the absence of climate change. There is strong regional variability (most adverse impacts would be in Asia), and considerable variability between climate models. In 2050, the range in increased exposure across 21 climate models under SRES A1b is 31-450 million people and 59 to 430 thousand km 2 of cropland, and the change in risk varies between −9 and +376 %. The paper presents impacts by region, and also presents relationships between change in global mean surface temperature and impacts on the global flood hazard. There are a number of caveats with the analysis; it is based on one global hydrological model only, the climate scenarios are constructed using pattern-scaling, and the precise impacts are sensitive to some of the assumptions in the definition and application.

Future bottlenecks in international river basins: where transboundary institutions, population growth and hydrological variability intersect

“…Our results correlate well with assessments made by the World Resources Institute (2015), Alfieri et al (2015) and Arnell and Gosling (2014). The World Resources Institute concludes that the number of people affected by floods will more than double by 2030, while Alfieri et al conclude that on average, flood peaks with a return period of 100 years or more will double in frequency within the next 30 years in Europe.…”

“…The global data-set of flood return and magnitude by Arnell and Gosling (2014) could be used in such analyses to address interesting social-ecological questions at the basin scale. Next to that, the quality and effectiveness of institutions was not part of this analysis; the results are purely based on paper evidence.…”

Mean and extreme precipitation over European river basins better simulated in a 25 km AGCM

“…Music and Caya, 2007;Middelkoop et al, 2001;Christensen et al, 2004), prediction at different lead times (e.g. Yuan et al, 2015;Arnell and Gosling, 2016;Scoccimarro et al, 2016), and extreme event attribution (e.g. Stott et al, 2016;Schaller et al, 2016).…”

Guidelines for the adaptation to floods in changing climate

“…For above mentioned reasons (Adger et al 2005;IPCC 2014c) or (Arnell and Gosling 2016) state that flood risk management in the global climate change context needs not only ''bottom-up'' but also ''top-down'' approaches. Combined approach seems to be a contemporary response for water resources management needs and leads to the policy called Integrated Water Resources Management (IWRM).…”