Seven centuries of reconstructed Brahmaputra River discharge demonstrate underestimated high discharge and flood hazard frequency

Mukund P Rao; Edward R Cook; Benjamin I Cook; Rosanne D D'Arrigo; Jonathan G Palmer; Upmanu Lall; Connie A Woodhouse; Brendan M Buckley; Maria Uriarte; Daniel A Bishop; Jun Jian; Peter J Webster

doi:10.1038/s41467-020-19795-6

Seven centuries of reconstructed Brahmaputra River discharge demonstrate underestimated high discharge and flood hazard frequency

Nat Commun. 2020 Nov 26;11(1):6017. doi: 10.1038/s41467-020-19795-6.

Authors

Mukund P Rao^{1

2}, Edward R Cook³, Benjamin I Cook^{4

5}, Rosanne D D'Arrigo³, Jonathan G Palmer⁶, Upmanu Lall⁷, Connie A Woodhouse⁸, Brendan M Buckley³, Maria Uriarte⁹, Daniel A Bishop^{3

10}, Jun Jian¹¹, Peter J Webster¹²

Affiliations

¹ Tree Ring Laboratory, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA. mukund24rao@gmail.com.
² Department of Earth and Environmental Science, Columbia University, New York, NY, 10027, USA. mukund24rao@gmail.com.
³ Tree Ring Laboratory, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA.
⁴ NASA Goddard Institute for Space Studies, New York, NY, 10025, USA.
⁵ Ocean & Climate Physics, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA.
⁶ ARC Centre of Excellence in Australian Biodiversity and Heritage, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.
⁷ Department of Earth and Environmental Engineering, Columbia University, New York, NY, 10027, USA.
⁸ School of Geography and Development, University of Arizona, Tucson, AZ, 85721, USA.
⁹ Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY, 10027, USA.
¹⁰ Department of Earth and Environmental Science, Columbia University, New York, NY, 10027, USA.
¹¹ Dalian Maritime University, Dalian, 116024, China.
¹² Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30318, USA.

Abstract

The lower Brahmaputra River in Bangladesh and Northeast India often floods during the monsoon season, with catastrophic consequences for people throughout the region. While most climate models predict an intensified monsoon and increase in flood risk with warming, robust baseline estimates of natural climate variability in the basin are limited by the short observational record. Here we use a new seven-century (1309-2004 C.E) tree-ring reconstruction of monsoon season Brahmaputra discharge to demonstrate that the early instrumental period (1956-1986 C.E.) ranks amongst the driest of the past seven centuries (13^th percentile). Further, flood hazard inferred from the recurrence frequency of high discharge years is severely underestimated by 24-38% in the instrumental record compared to previous centuries and climate model projections. A focus on only recent observations will therefore be insufficient to accurately characterise flood hazard risk in the region, both in the context of natural variability and climate change.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.