The Impact of Climate Change on IDF Curves Across Canada

English Abstract:

The frequency and intensity of extreme events (such as floods, droughts, and others) have been changing dramatically in the past few decades. Many studies indicate that these changes are due to the effects of a changing climate. Increase in extreme precipitation events is majorly altering the planning, design and operation of hydraulic infrastructure. In this study we present the spatio-temporal changes of rainfall intensity-duration-frequency (IDF) curves under future climatic conditions across Canada. The updated IDF curves are derived using an equidistance quantile matching method. The advantage of this method is that it avoids the use of spatial downscaling/disaggregation methods. The sub-daily annual maximum intensities are obtained for 758 climate stations across Canada. The recorded length of the data ranges from 3 to 75 years. In this study the stations with record lengths greater than 10 years are selected for the analysis. The climate data is obtained from 17 Global Climate Models (GCM) of the Coupled Model Intercomparison Project Phase 5 (CMIP 5) adopted in the fifth assessment report (AR5) of Intergovernmental Panel on Climate Change (IPCC). Three future scenarios, namely representative concentration pathways (RCP) 2.6, 4.5 and 8.0 are selected to represent the climatic conditions for the year 2100. The results show that the increase in precipitation is consistent with the RCP scenarios across Canada; i.e. RCP 8.5 shows a greater increase in precipitation than RCP 4.5 which in-turn is higher than RCP 2.6. The ensemble of percentage changes from current to future IDF curves are presented for four indices: median change, mean change, maximum change, and minimum change. Among all four indices the minimum change in the IDF curves at all the stations in Canada is lower than the observed historical values. The maximum and mean changes for many stations show unrealistically large percentage of changes with respect to historical IDF curves. It is also observed that the length of the data has a significant effect on the future IDF curves. More changes are observed in future IDF curves that are developed from data of shorter record lengths. The future IDF curves across Canada offer valuable information for the regionalization of precipitation stations and its effect on municipal planning and management.