H051-05
Quantifying the effect of dams in reducing global flood exposure under climate change

Tuesday, 8 December 2020: 19:16
Virtual
Julien Eric Boulange, National Institute for Environmental Studies, Tsukuba, Japan, Naota Hanasaki, National Institute for Environmental Studies, Ibaraki, Japan, Dai Yamazaki, The University of Tokyo, Institute of Industrial Sciences, Tokyo, Japan and Yadu Pokhrel, Michigan State University, Department of Civil and Environmental Engineering, East Lansing, MI, United States
Recorded Presentation
Abstract:
Flood risk was reported to increase in the future due to climate change and population growth1,2. Recent and past studies have derived plausible climate change impacts on global flood risk, dams were physically implemented into the simulation tools3.

In this research, the role of dams on future flood risk under climate change is quantified by simulating the global hydrological cycle, including floodplain dynamics, and considering flow regulation by dams.

Globally, the population exposed to a 1 in a 100 year flood in our simulation was, on average, 9.4 million people, close to the estimate of 5.6 million people indicated in Hirabayashi et al.,4 and the Dartmouth Flood Observatory database which estimated this number as 11.9 million people. Downstream of dams, 2.4 (1.1–4.6) million/year people (the first and third quartile given in bracket indicate the uncertainty across GCMs) were exposed to river flood. Keeping population constant, toward the end of the 21st century population exposure was projected to increase to 9.1 (4.7–18.1) and 15.3 (8.4–27.2) million/year people for RCP2.6 and RCP6.0, respectively.

However, dam reduced the number of exposed people by 20.1% and 12.6% (i.e., on average reducing the number of people exposed to river flood by 1.8 (1.1–3.0) and 1.9 (1.0–2.9) million for RCP2.6 and RCP6.0. respectively) at the end of the 21st century. For the same period, accounting for population growth by mean of the Shared Socioeconomic Pathways (SSPs), downstream of dams the population exposed to river flood was reduced by (lowest and highest values across the five SSP scenarios) 20. 6%–32.0% and 7.0%–16.8%, for RCP2.6 and RCP6.0, respectively, comparing with a simulation with no dam implementation.

References:

  1. Prein, A. F. et al. The future intensification of hourly precipitation extremes. Nature Climate Change 7, 48 (2016).
  2. Milly, P. C. D., Wetherald, R. T., Dunne, K. A. & Delworth, T. L. Increasing risk of great floods in a changing climate. Nature 415, 514–517 (2002).
  3. Dottori, F. et al. Increased human and economic losses from river flooding with anthropogenic warming. Nature Climate Change 8, 781–786 (2018).
  4. Hirabayashi, Y. et al. Global flood risk under climate change. Nature Climate Change 3, 816 (2013).
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