Rainfall extremes under future climate change with implications for urban flood risk in kathmandu, Nepal

Dibesh Shrestha, Divas B. Basnyat, Januka Gyawali, Maggie Creed, Hugh Sinclair, Brian Golding, Manoranjan Muthusamy, Shankar Shrestha, C. Scott Watson, Divya L. Subedi, Rojina Haiju

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Increased rainfall extremes cause severe urban flooding in cities with adverse socio-economic consequences, and Kathmandu city is no exception. Rainfall events are projected to become more intense and frequent in a warm and wet future, and they pose a major challenge to the sustainable development of Kathmandu city. This paper analyses historical extreme rainfall patterns across the city and uses these as the basis for future projections in combination with a range of General Circulation Models. Future projections of extreme rainfall are then fed into the numerical flood model HAIL-CAESAR (Lisflood), using a high-resolution digital elevation model of Kathmandu. We show that rainfall intensity, such as the 24-h maximum rainfall (RX1day), is projected to increase by up to 72% in the future, and the historical 100-year return period rainfall will become a 20 or 25-year return period rainfall. The flood modelling results show that the future flood hazard (magnitude and extent) will increase. The historical 100-year return period flood discharge will correspond to a 25-year return period future flood. A 100-year period flood discharge is likely to increase up to 72% (37% median) in the future. Area of land inundated by more than 1 m in a 100-year return period flood event could increase from 11.7 km2 to 23 km2 in the future. Furthermore, the location and timing of rainfall maxima affect the peak, timing, and location of flood hazards. This analysis can serve as a scientific basis to assess future flood-induced risk in Kathmandu in response to climate change.
Original languageEnglish
Article number103997
JournalInternational Journal of Disaster Risk Reduction
Volume97
Early online date9 Sept 2023
DOIs
Publication statusPublished - 15 Oct 2023

Keywords / Materials (for Non-textual outputs)

  • Climate change
  • Kathmandu
  • Lisflood
  • RX1day rainfall
  • Rainfall extreme
  • Urban flood

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