Practical thresholds for separating erosive and non-erosive storms

摘要

Determination of a practical threshold for separating erosive and non-erosive rainfall events can reduce the amount of work necessary to read rainfall charts and to calculate rainfall erosivity. The objective of this study was to develop a method of determining practical thresholds for erosive rainfall events and to evaluate its effectiveness for calculation of erosivity. Rainfall and runoff data measured for three plots and a small watershed from 1961 to 1969 at the Zizhou experimental station of the Yellow River Basin in China were used. Three thresholds for separating erosive events were given by using different types of rainfall data: (1) 12 mm for storm rainfall amount, (2) 2.4 mm h{sup}(-1) for average rainfall intensity, and (3) 13.3 mm h{sup}(-1) for the maximum 30-minute rainfall intensity. All methods had less than 0.1% overall error in the prediction of the erosivity value. Peak intensity provided the greatest accuracy for separating erosive rains, followed by rainfall intensity and then rainfall amount. A total of 79%, 77%, and 88% of the total number of events were omitted from the calculations using rainfall amount, average rainfall intensity, and 30-minute peak intensity, respectively. Any of the above three thresholds may be used according to data availability and desired accuracy of the erosivity estimation.