The IDF Analysis tool charts the relationship between rainfall intensity, rainfall duration, and storm return period (frequency) for a specified wet weather event.
From the Monitoring Station pop-up menu, select the bottom icon (Analysis Tools) and IDF Analysis from the drop-down menu. Alternatively, you can select IDF Analysis under Tools in the hamburger menu, in which case you would have to define the Organization, Project, Service, and Monitoring Station in addition to the configurations noted below.
Under “General” in the “Configuration” tab, the user determines the design storm to be used and confirms the station’s Time of Concentration. The user can also check whether to display the IDF curve using a logarithmic or linear scale on the X Axis.
Under “Curves” in the “Configuration” tab, the user can “Configure Events,” choosing minimum storm size (default 15mm volume), inter-event dry period (default 12 hours), and time extent / entire time range.
The user may then select a specific wet weather event(s) in the “Events” tab under “Curves.” Under the “Design Storm” tab, the user may select 2, 5, 10, 25, 50, and/or 100-year storm events. Finally, under the “Time Range” tab, the user may use total precipitation over a time range (the user must check the box “Time Range Event” for the time range to be displayed on the chart).
On the IDF Analysis chart, the user may hover over the event and design storm lines, displaying the time step and intensity.
Below the graphical chart, information regarding the event and design storms is displayed in tabular format:
- Total Precipitation
- Peak Rainfall Intensity over 5, 10, 15, 20, 30 minutes and 1, 2, 3, 4, 6, 12, and 24 hours
The user may print the IDF chart, or download as .png, .jpeg, .svg vector image, or PDF.