NAHRIM Technical Guide No. 1 - Estimation of Future Design Rainstorm Under the Climate Change Scenario in Peninsular Malaysia (2023)
The Intergovernmental Panel on Climate Change (IPCC) adopted Representative Concentration Pathways (RCPs) for its comprehensive spectrum of future greenhouse gas emission scenarios for its Fifth Assessment Report (AR5) in 2014. NAHRIM has continued to update its Regional Hydroclimate Model (RegHCM) and investigate the impact of climate change on the hydro-climate of the country based on IPCC AR5 over the geographical region of Peninsular Malaysia, Sabah and Sarawak, with the latest publication of “The Impact of Climate Change on the Hydro-Climate of Malaysia Based on IPCC Fifth Assessment Report in 2021. Subsequent to this publication, NAHRIM has taken the initiative to update Technical Guide No. 1 (Estimation of Future Design Rainstorm under the Climate Change Scenario in Peninsular Malaysia) which was last completed in 2013 based on IPCC Fourth Assessment Report. Among the improvements included in this updated Technical Guide No. 1 are on the following various specifics: IPCC’s Fifth Assessment Report (from AR4 to AR5), types of Global Climate Models (GCMs), scenarios (from stabilisation to RCPs scenarios), finer spatial resolution (from spatial grid 9-km to 6-km resolution), and time resolution (from daily to hourly for Peninsular Malaysia). A total of 154 rainfall stations (managed by DID) in Peninsular Malaysia were selected to be analysed for the calculation of climate change factor (CCF) associated with return periods of 2, 5, 10, 20, 25, 50, and 100 years. Sub-daily climate change factor is produced by which the daily precipitation data from RCP scenarios were downscaled using Equidistance Quantile Matching (EQM) method. In addition to the 154 at-site CCF values, CCF values for ungauged locations have been derived for regions (Eastern, Southern, West Central and Northern), as well as 10 km and 20 km spatial resolution gridded CCF maps. The average at-site CCF values for 154 rainfall stations in Peninsular Malaysia are estimated to be 1.12, 1.15, 1.17, 1.18, 1.18, 1.19 and 1.20 for return periods of 2, 5, 10, 20, 25, 50, and 100 years, respectively. It indicates an increment of 12% to 20% of rainfall intensity for return periods of 2 to 100 years, which leads to an increment of estimated design flood peak that needs to be considered in hydraulic structure sizing. This technical guide is useful to assist engineers, hydrologists and decision makers in designing, planning and developing water-related infrastructure in response to shifting climatic conditions. It will serve to introduce an approach of quantifying the scale of climatic change to surface water systems, particularly due to variability and alterations in precipitation pattern, through the development of at-site and regional climate change factor and formulation of the developed Intensity-Duration-Frequency relationship by Department of Irrigation and Drainage (DID) for future conditions.
Authors
Abstract
The Intergovernmental Panel on Climate Change (IPCC) adopted Representative Concentration Pathways (RCPs) for its comprehensive spectrum of future greenhouse gas emission scenarios for its Fifth Assessment Report (AR5) in 2014. NAHRIM has continued to update its Regional Hydroclimate Model (RegHCM) and investigate the impact of climate change on the hydro-climate of the country based on IPCC AR5 over the geographical region of Peninsular Malaysia, Sabah and Sarawak, with the latest publication of “The Impact of Climate Change on the Hydro-Climate of Malaysia Based on IPCC Fifth Assessment Report in 2021. Subsequent to this publication, NAHRIM has taken the initiative to update Technical Guide No. 1 (Estimation of Future Design Rainstorm under the Climate Change Scenario in Peninsular Malaysia) which was last completed in 2013 based on IPCC Fourth Assessment Report. Among the improvements included in this updated Technical Guide No. 1 are on the following various specifics: IPCC’s Fifth Assessment Report (from AR4 to AR5), types of Global Climate Models (GCMs), scenarios (from stabilisation to RCPs scenarios), finer spatial resolution (from spatial grid 9-km to 6-km resolution), and time resolution (from daily to hourly for Peninsular Malaysia). A total of 154 rainfall stations (managed by DID) in Peninsular Malaysia were selected to be analysed for the calculation of climate change factor (CCF) associated with return periods of 2, 5, 10, 20, 25, 50, and 100 years. Sub-daily climate change factor is produced by which the daily precipitation data from RCP scenarios were downscaled using Equidistance Quantile Matching (EQM) method. In addition to the 154 at-site CCF values, CCF values for ungauged locations have been derived for regions (Eastern, Southern, West Central and Northern), as well as 10 km and 20 km spatial resolution gridded CCF maps. The average at-site CCF values for 154 rainfall stations in Peninsular Malaysia are estimated to be 1.12, 1.15, 1.17, 1.18, 1.18, 1.19 and 1.20 for return periods of 2, 5, 10, 20, 25, 50, and 100 years, respectively. It indicates an increment of 12% to 20% of rainfall intensity for return periods of 2 to 100 years, which leads to an increment of estimated design flood peak that needs to be considered in hydraulic structure sizing. This technical guide is useful to assist engineers, hydrologists and decision makers in designing, planning and developing water-related infrastructure in response to shifting climatic conditions. It will serve to introduce an approach of quantifying the scale of climatic change to surface water systems, particularly due to variability and alterations in precipitation pattern, through the development of at-site and regional climate change factor and formulation of the developed Intensity-Duration-Frequency relationship by Department of Irrigation and Drainage (DID) for future conditions.
Citation
IR. MOHD ZAKI BIN MAT AMIN, IR. AZMAN MAT JUSOH, NOOR HISHAM BIN AB GHANI, ZURINA ZAINOL, DR. THIAN SIAW YIN, GOH YEE CAI. 2023. NAHRIM Technical Guide No. 1 - Estimation of Future Design Rainstorm Under the Climate Change Scenario in Peninsular Malaysia (2023). Digital NAHRIM Publication Repository.