The I/I Event Analysis tool calculates inflow and infiltration for a specified wet weather event.

From the Monitoring Station pop-up menu, select the bottom icon (Analysis Tools) and I/I Event Analysis from the drop-down menu. Alternatively, you can select I/I Event 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.

The user must first confirm the key inputs for the site and apply a filter for the wet weather event in the “Configuration” tab:

  • The total area of the contributing catchment (defined in Station Details under the “Attributes” tab)
  • The Time of Concentration of the catchment (the time needed for water to flow from the most remote point in the catchment to the outlet), in minutes (defined in Station Details under the “Attributes” tab)
  • The minimum wet weather event volume threshold, to filter out smaller/insignificant storms (the tool defaults to 15mm but can be modified); once selected, the user must “Load Events” in order to use the “Event Date Selection” to select a single wet weather event to analyze.

A red asterisk denotes required inputs.

The user can further configure the analysis:

  • Display Options: display estimated dry weather flow and measured flow, or both (the tool defaults to show both)
  • Time Range: once a wet weather event has been selected, the tool automatically defines a time range, but this can be edited by the user
  • Inter-Event Dry Period: defaulted to 12 hours, this can be modified by the user to better define the start/end of storm events
  • Precipitation Display Timestep: defaulted to the Time of Concentration, the user can view the precipitation data in 5, 10, 30, 60, 90, and 120 minute timesteps

The graphical display plots precipitation, estimated dry weather flow, measured flow, and calculated inflow and infiltration. The chart is interactive: hovering over any point on the X Axis of the chart (time) gives the user the exact values for estimated DWF, measured flow, and I/I. Similarly, hovering over the precipitation shows the volume of rainfall for the given timestep.

Below the chart, a table details important I/I metrics:

  • Catchment Area
  • Time of Concentration (Tc)
  • Total Precipitation (for the event)
  • Duration of the Storm
  • Peak Precipitation Intensity over Tc
  • Return Period over Tc
  • Time of Peak Measured Flow
  • Peak Measured Flow
  • Peak Measured Depth
  • Total Measured Flow Volume during Event
  • Time of Peak I/I Flow
  • Peak I/I Rate
  • Estimated Dry Weather Flow at Time of Peak I/I Flow
  • Peak I/I Flow
  • Total I/I Flow Volume during Event
  • Volumetric Coefficient (Cv%) (the percentage of the volume of rainfall that became I/I in the sewers)
  • Peak I/I Coefficient
  • Hourly Wet Weather Peaking Factor (the ratio of peak hourly wet weather flow to average daily dry weather flow)
  • Instantaneous Wet Weather Peaking Factor (the ratio of peak wet weather flow to average daily dry weather flow)

The I/I Event Analysis output may be downloaded by the user as a .csv.


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