Preprints
https://doi.org/10.5194/hess-2021-97
https://doi.org/10.5194/hess-2021-97

  09 Apr 2021

09 Apr 2021

Review status: this preprint is currently under review for the journal HESS.

Hydrometeorological drivers of flood characteristics in the Brahmaputra river basin in Bangladesh

Sazzad Hossain1,2, Hannah L. Cloke1,3,4,5, Andrea Ficchì1, Andrew G. Turner3,6, and Elisabeth M. Stephens1 Sazzad Hossain et al.
  • 1Department of Geography and Environmental Science, University of Reading, Reading, UK
  • 2Flood Forecasting and Warning Centre, BWDB, Dhaka, Bangladesh
  • 3Department of Meteorology, University of Reading, Reading, UK
  • 4Department of Earth Sciences, Uppsala University, Uppsala, Sweden
  • 5Centre of Natural Hazards and Disaster Science, CNDS, Uppsala, Sweden
  • 6National Centre for Atmospheric Science, University of Reading, Reading, UK

Abstract. While flooding is an annual occurrence in the Brahmaputra basin during the South Asian summer monsoon, there is large variability in the flood characteristics that drive risk: flood duration, rate of water level rise and peak water level. The aim of this study is to understand the key hydrometeorological drivers influencing these flood characteristics. We analyse hydrometeorological time series of the last 33 years to understand flood dynamics focusing on three extraordinary floods in 1998 (long duration), 2017 (rapid rise) and 2019 (high water level). We find that long duration floods in the basin have been driven by basin-wide seasonal rainfall extremes associated with the development phase of strong La Niña events, whereas floods with a rapid rate of rise have been driven by more localized rainfall falling in a hydrological ‘sweet spot’ that leads to a concurrent contribution from the tributaries into the main stem of the river. We find that recent record high water levels are not coincident with extreme river flows, hinting that sedimentation and morphological changes are also important drivers of flood risk that should be further investigated. Understanding these drivers is essential for flood forecasting and early warning and also to study the impact of future climate change on flood.

Sazzad Hossain et al.

Status: open (until 28 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-97: Hydrometeorological drivers of flood characteristics in the Brahmaputra river basin in Bangladesh by Hossain et al.', Anonymous Referee #1, 28 Jun 2021 reply
  • RC2: 'Comment on hess-2021-97', Anonymous Referee #2, 18 Jul 2021 reply

Sazzad Hossain et al.

Sazzad Hossain et al.

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Short summary
Hydrometeorological drivers are investigated to study three different flood types: long duration, rapid rise and high water level of the Brahmaputra river basin in Bangladesh. Our results reveal that long duration floods have been driven by basin-wide rainfall whereas rapid rate of rise due to more localized rainfall. We find that recent record high water levels are not coincident with extreme river flows. Understanding these drivers is key for flood forecasting and early warning.