IDF Curves 101

Learn what an IDF curve is, including an interactive walk-through of how to read them, and learn how Environment and Climate Change Canada produces IDF curves.

Time to completion
5 min

Key Messages

  • Historical Intensity-Duration-Frequency (IDF) curves are graphical tools that describe the likelihood of a range of extreme rainfall events.  Environment and Climate Change Canada (ECCC) produces IDF curves using statistical techniques and records of past rainfall.
  • IDF curves are used by a wide range of professionals – including engineers, water resource managers, and urban and regional planners – to manage impacts and risks related to extreme rainfall.
  • Practitioners should understand how to use, read and interpret IDF curves before using them for decision-making.  They should also be aware of key challenges and limitations in measuring extreme rainfall and creating IDF curves, in order to avoid misuse.
  • Historical IDF curves alone cannot be used to assess future extreme rainfall conditions, which are expected to shift considerably over time due to climate change. Methods exist to ‘shift’ historical IDF curves to account for climate change.
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