You can develop the i-d-f curves for the Richmond area from
Bulletin 71, which gives depth-frequency and duration data for a nine state region including Kentucky. The publication is Rainfall Frequency Atlas of the Midwest by Huff and Angel, a combined publication of the Illinois State Water Survey and the Midwestern Climate Center. It is filed as MCC Research Report 92-03, ISSN 0360-9804. I don't know if it is available on the net.