Introducing CSA W231-2024: Developing and Interpreting Intensity-Duration-Frequency (IDF) Information Under a Changing Climate

Intensity-Duration-Frequency (IDF) curves are essential tools for engineers, hydrologists, urban planners, and water resource managers in designing infrastructure that can withstand extreme rainfall events. However, with the increasing evidence of climate change in Canada, relying solely on historical rainfall data to derive IDF curves is no longer sufficient. The newly developed CSA W231-2024: Developing and Interpreting Intensity-Duration-Frequency (IDF) Information Under a Changing Climate provides a structured methodology for incorporating future climate projections into IDF curves estimations, ensuring that infrastructure design accounts for the projected increase in the frequency and intensity of extreme rainfall events.

This presentation will outline the key principles of the new standard. First, it will provide an overview of the steps required to derive historical IDF curves. Next, the methodology for updating these curves using climate model projections and rainfall-temperature scaling based on the Clausius-Clapeyron relationship will be discussed. The standard also addresses key sources of uncertainty in estimating future rainfall extremes and provides a framework for integrating these uncertainties based on the intended application. Additionally, guidance is given on the selection of appropriate emissions scenarios to improve the robustness of future IDF curves estimations. Finally, a practical demonstration using available online datasets will illustrate how practitioners can apply the proposed methodology in real-world applications.

In short, CSA W231-2024 represents a significant advancement in equipping practitioners with the tools needed to design climate-resilient infrastructure. This standard will also support decision-makers in adapting infrastructure planning and policy to the reality of climate change.

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