Effect of minimum inter-event time for rainfall event separation on rainfall properties and rainfall erosivity in a humid area of southern China

An appropriate rainfall event definition helps to have more explanatory power in research on the effect of rainfall on runoff and soil erosion. The constant minimum inter-event time (MIT) criterion is a widely accepted method used to delineate independent rainfall events from continuous rainfall records. To explore the effects of the MIT selection on rainfall event properties, rainfall erosivity and its relationship with eroded sediment, 5-min interval rainfall data from 2016 to 2021 and runoff data from 2019 to 2021 were observed continuously for a bare plot site in a humid area of southern China. The results showed that increase in the MIT criteria had an important impact on the properties of erosive rainfall events, such as reducing rainfall frequency, increasing duration, and reducing the average rainfall intensity. Furthermore, the MIT increased continuously, changed the statistical relationship between rainfall and sediment erosion, and logarithmically increased the rainfall threshold for a certain cumulative eroded sediment probability. With continuous increase in the MIT, the total kinetic energy, maximum 30 min intensity, and rainfall erosivity of rainfall events increased as a power function (r2 greater than 0.97). On the rainfall event scale, the linear relationship between EI30 and eroded sediment is the closest when MIT = 4 h. Thus, more attention should be given to the use of the MIT criterion for rainfall event identification, as it relates to the properties of rainfall events and rainfall erosivity.