Calculation of a regression constant for calculating rainfall intensities I (l/s/ha) for the entire World has been implemented in the box Design flow in StormTac Web. The function is derived from the equation developed by Dahlström (2010) and uses a target search (goal seek) function to iterate a regression constant, alpha, which controls the rain intensities over input data in the form of selected return time (year), specified rain durations (min) and rain intensities (l/s/ha). The generated regression constant alpha can be used for rain intensities for optional rainfall durations and replaces the default values in the model. The result will be different local/regional rainfall intensities used to calculate design flows and the required flow detention volume. If you want the model to always start with a calculated regression constant, you can manually enter it under the sheet (tab) Settings, but this should not be done if the license is used by offices in different locations.
Alternatively, you can, as before, manually enter each rain intensity for specified durations in the boxes (tables) at the boxes Design flow and Flow detention. The latter provides more accurate values, but the alpha value can be used for all return times.