Assessment of rainfall erosivity and its spatial and temporal variabilities: Case study of the Penedès area (NE Spain)

• Rainfall erosivity based on different time scale data
• Spatial and temporal variabilities of rainfall erosivity in NE Spain
• The need for more detailed time scales to estimate rainfall erosivity
• Changes in rainfall erosivity at event scale
• Changes in erosive event distribution within the year

In this paper, rainfall erosivity based on different time intervals was evaluated for the Penedès region (Northeast Spain), an area affected by high erosion processes. Characteristics of storms (duration, maximum intensity, depth and frequency) recorded in the area were analysed using a tipping-bucket series, which was used to estimate rainfall erosivity from hourly data (1997–2013), recorded at four observatories, and daily data (1960–2013) recorded at two observatories of the study area. The relationships between data obtained from different intervals were evaluated using the coefficient of determination (R2), the ratio of the root mean square error to standard deviation (RSR), the percent bias (PBIAS), and the Nash–Sutcliffe efficiency (NSE). Spatial and temporal variabilities were evaluated for the analysed periods, considering annual and monthly rainfall erosivities, the number of erosive events and its distribution within the year, the maximum event erosivity and the maximum precipitation event.Annual rainfall erosivity in the study area presented a high degree of variability from year to year, ranging from about 500 to over 2000 MJ ha−1 mm h−1. However, during the last decades the number of erosive events has increased and very high values of event erosivity were observed in the analysed meteorological stations. In some cases, event erosivity was of the same order of magnitude as average annual erosivity. The changes in event erosivity were not uniform. The number of low erosive events increased at all observatories, but high erosive events only increased at one. The results confirm the need for detailed time scale data for good estimation of high erosive events. Estimations based on daily data may, however, be useful to compare average erosivity within an area. A change in rainfall erosivity within the year was observed, with an increase in spring rainfall erosivity despite a decrease in total rainfall. In autumn, the number of erosive events decreased in September, but the individual event erosivity increased reaching very high values.