I'm trying to obtain the intensity value from the IDF curve for a 25 year storm. The time of concentration is 17 min. Since 25 year storm is not there, how would I interpolate? Do I just take the average of the 20 year and 50 year value? Please let me know what approximate value you get =] Thank you.
![idf.jpg idf.jpg](https://cdn.imagearchive.com/engineerboards/data/attachments/5/5510-f40971ee020d9b1707ce33420dfeadbd.jpg)
![idf.jpg idf.jpg](https://cdn.imagearchive.com/engineerboards/data/attachments/5/5510-f40971ee020d9b1707ce33420dfeadbd.jpg)