IDF Polynomial Log Equation Dialog Box
The IDF Polynomial Log Equation definition type calculates the storm data using the following equation:
![](GUID-0D0E49DD-F858-4EAA-9061-A9BCABFF4461-low.png)
Where
i = rainfall intensity
D= rainfall duration
a, b, c, d = rainfall equation coefficients
![](GUID-31F8B83F-BC9D-4643-AD0C-132BF04FCF31-low.png)
Enter the Return Event and the values for the a (log), b (log), and c (log), and d (log) coefficients. Click the New button to add a row to the table, and Delete to remove the currently highlighted row.