426 / 2024-03-15 20:57:22

Analysis of extreme rainfall during major flooding in Kuala Lumpur and Selangor, Malaysia in December 2021

depth duration frequency,flood,extreme precipitation,recurrence interval

Subtheme 1: Water-related Hazard and Risk Reduction > Topic 1: Water Hazard Under Climate Change

Kuala Lumpur and Selangor, the most developed region in Malaysia, experienced unexpected floods in December 2021 which caused huge losses in terms of lives and properties. Initial raingauge readings revealed extreme rainfall occurring during the flood event. This study characterises the severity of the extreme rainfall during the floods and examines the spatio-temporal extent of the rainfall from 2021-12-17 00:00 to 2021-12-19 00:00 within the region. Rainfall spatial distribution maps were plotted using the nearest neighbour (NN) interpolation method reveals widespread high-intensity, long duration rainfall over large areas within Kuala Lumpur and Selangor, especially in Klang and Langat river basins, which caused severe flooding throughout both basins. The highest rainfall was concentrated in district of Klang and Klang river basin. The highest 2-day rainfalls were comparable with long-term monthly rainfall in the region. Cumulative 2-day rainfall at HP1 (design rainfall guideline) stations were plotted against depth-duration-frequency (DDF) curves. Based on the HP1 procedure, the cumulative rainfall at one of the stations reached 500-year ARI and five other stations at 200-year ARI. However, only two of these stations are among the 20 stations which recorded the highest 2-day cumulative rainfall during the period. The results demonstrate an exceptionally high rainfall intensity, highlighting the need to reassess the adequacy of the existing flood mitigation structures in the face of a changing climate.