DDF Rainfall Data
The DDF Rainfall Window
Once you purchase a catchment or a point data, you can access the DDF Rainfall window clicking on the blue Rainfall button . DDF Science Overview provides information on the DDF models.
This window allows you to perform depth-duration-frequency (DDF) calculations for the selected catchment/point as well as for the 1km grid cell closer to the catchment outlet, with an interactive graph displaying the most common return periods.
Automatic choices for advanced parameters are available to simplify use, e.g. choice between annual maximum (AM) and peaks-over-threshold (POT) return period scales, and fixed and sliding event durations. Certain combinations of depth, duration, or return period will automatically switch these options. For example, setting a return period of 6 months will disable the AM return period scale option and switch to POT.
You can view either the FEH13 and FEH22 DDF models via the switch in the top right side of the windows. The legacy FEH99 DDF model is available using the switch drop-down button. Note that FEH99 is only available for catchment data.
In Design Rainfall mode rainfall data can be exported to CSV by clicking the Export button. The rainfall data is represented as a matrix of depths for standard return periods and durations. The export will vary slightly depending if the user has entered a duration and return period and performed a depth calculation or not. If a depth calculation has been performed extra header lines will be present in the CSV file with details of the calculation performed. If a return period has been used that is not one of the standard return periods an extra column will also be added to the output containing depths for the custom return period.
Please note that third party tools that are able to import FEH Web Service rainfall CSV data may not work correctly with the extra data present. In this case it is suggested to press the Reset button to clear any current parameters and perform a basic export.