Rainfall extremes under future climate change with implications for urban flood risk in Kathmandu, Nepal
Authors:Shrestha, Dibesh Basnyat, Divas B. Gyawali, Januka Creed, Maggie J. Sinclair, Hugh D. Golding, Brian Muthusamy, Manoranjan Shrestha, Shankar Watson, C. Scott Subedi, Divya L. Haiju, Rojina
Volume:97
DOI:10.1016/j.ijdrr.2023.103997
Published:2023
Document Type:Article
Abstract: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 annual maximum 1-day 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.
Author Information
Corresponding Author:Shrestha, D; Basnyat, DB (corresponding author), Nepal Dev Res Inst NDRI, Water & Climate Program, Lalitpur, Nepal.
Reprint Address:Shrestha, D; Basnyat, DB (corresponding author), Nepal Dev Res Inst NDRI, Water & Climate Program, Lalitpur, Nepal.
Addresses:[Shrestha, Dibesh; Basnyat, Divas B.; Shrestha, Shankar; Subedi, Divya L.; Haiju, Rojina] Nepal Dev Res Inst NDRI, Water & Climate Program, Lalitpur, Nepal; [Gyawali, Januka] Pract Act, Kathmandu, Nepal; [Creed, Maggie J.] Univ Glasgow, James Watt Sch Engn, Glasgow G12 8QQ, Scotland; [Sinclair, Hugh D.] Univ Edinburgh, Sch Geosci, Drummond St, Edinburgh EH8 9XP, Scotland; [Golding, Brian] Met Off, Exeter EX1 3PB, Devon, England; [Muthusamy, Manoranjan] FloodFlash, London E1 5LN, England; [Watson, C. Scott] Univ Leeds, Sch Earth & Environm, COMET, Leeds LS2 9JT, England
E-mail Addresses:dibeshshrestha@live.com; divas@ndri.org.np