This video shows how to use the Rainfall IDF Analysis.
IDF Instructions
This section explains how to use the Rainfall Intensity-Duration-Frequency (IDF) Analysis. This analysis is useful when you want to look at rainfall data relative to historical values. Like all reports in Flowworks, it is updated as frequently as new data is received. This allows you to use it to look at storms as they develop in real time.
Once you have logged in and selected ‘Analysis’ in ‘My Network’ you will see ‘Rainfall IDF Analysis’ in the lower half of the ‘My Network’ task bar.
Basic IDF Instruction
- Select a station
- Select date range
- Generate IDF Analysis
- Interpreting Results
- Printing Results
1. Select a station
Select the rainfall station site you wish to analyze from the dropdown menu. For this example we will select the station Demo Sanitary- Metric.
2. Select Date Range
Select the date range you would like graphed. This can be done by customizing the date range by using the ‘Start Date’ and ‘End Date’ calendars to select the dates.
For this example we will customize the date range from January 1, 2009 to February 1, 2009. You can either scroll through the monthly calendars by clicking on the small arrows on the top left and right corners of the calendars or you can click on the month and year to select the desired dates.
OR
Start and stop times for events are optional and can also be selected.
3. Generate IDF Analysis
Once you have selected the station and date range, click on ‘Generate IDF Analysis’ and a graph should appear showing the IDF plot for the station
4. Interpreting Results
The colored lines on the graph represent the historical IDF information for the site. This information is obtained from either the National Oceanic and Atmospheric Administration or Environment Canada. You can also supply your own rainfall data if you have more detailed local records.
The red line shows the data for the storm we previously selected overlayed on top of the historical values. If the red line crosses over the historical values for any given rainfall duration, it indicates that a significant value has been reached at that duration. For example, in the graph below the red line crosses the 2 Year historical line between the 12 hour and 24 hour durations indicating that for that duration the event was a 2 year event.
At the bottom of the graph, the total amount of rain and the length of the chosen event are shown. A table below that shows the amount of rain for the event for each duration in mm/hr or in/hr compared to historical amounts. For example, in the table below we see that the 24 hour duration rain was 3.0 mm/hr and that the 2 year 24 hour historical amount is 2.8 mm/hr, indicating that the event analyzed was slightly higher than a 2 year event at the 24 hour duration.
5. Printing Results
The whole IDF plot page prints neatly on an 8 ½ x 11 portrait page by
