Spatial and temporal variations in rainfall erosivity and erosivity density in South Korea

Rainfall erosivity is one of the key parameters in Universal Soil Loss Equation (USLE), which has been used to predict the amount of soil loss by water for 50 years. Investigating spatial and temporal trends in rainfall erosivity is important for soil and water conservation planning. Rainfall erosivity (the R factors) in many regions is expected to be altered due to changes in rainfall patterns related to rainfall intensity and the frequency and spatial distribution of storm events that may occur with climate change. In South Korea, some researchers have studied temporal variation in meteorological and hydrologic phenomena with climate change, particularly temperature and precipitation trends. The purpose of this study is to investigate spatial and temporal variations in rainfall erosivity and erosivity density and to improve our understanding of the evolution of rainfall erosivity in South Korea. First, we calculated rainfall erosivity at 46 stations for 1961-2015 using 5-min precipitation data. Second, we examined spatial and temporal variability in the rainfall erosivity; trends and change points of R factor time series and analyzed the relationships between rainfall erosivity and climate indices (such as the precipitation amount, number of effective events, and duration). Four trend tests such as the t-test, MK test, modified version of the MK test, and BBS-MK test, were used to detect trends in the annual R factor, total duration, number of effective events, total depth, mean maximum 30-min intensity, and total kinetic energy time series for all employed stations. The results provide insights into the evolution of rainfall erosivity and the effects of large-scale climatic circulation on rainfall erosivity.