Effects of Rainfall Intensity on Runoff Curve Numbers

• Main Author: Hawkins, R. H.
• Other Authors: Watershed Science Unit, Department of Forestry and Outdoor Recreation, Utah State University, Logan, Utah, 84322
• Language: en_US
• Published: Arizona-Nevada Academy of Science 1978
• Subjects: Hydrology > Arizona.; Water resources development > Arizona.; Hydrology > Southwestern states.; Water resources development > Southwestern states.; Rainfall-runoff relationships; Storm runoff; Runoff coefficient; Curves; Rainfall intensity; Infiltration; Forecasting; Hydrologic equation; Measurement; Design criteria
• Online Access: http://hdl.handle.net/10150/301034

From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona === The runoff curve number rainfall- runoff relationships may be defined in two ways: (1) by formula, which uses total storm rainfall and a curve number, but not intensity or duration descriptors; and (2) rainfall loss accounting using a 4, rate and a specific intensity duration distribution of the function i(t) = 1.5P(5(1 +24t /T)-(1/2)-1) /T, where i(t) is the intensity at time t for a storm of duration T. Thus, the curve number method is found to be a special case of φ index loss accounting. The two methods are reconciled through the identity 1.2S = φT, leading to the relationship CN - 1200/(12 +φT). The effects of rainfall intensity on curve number are felt through deviations from the necessary causative intensity - duration curve. Some sample alternate distributions are explored and the effects on curve number shown. Limitations are discussed.