Abstract
Abstract. Rainfall erosivity refers to the ability of precipitation to erode soil, and depends on characteristics such as its total volume, duration, and intensity and amount of energy released by raindrops. Despite the relevance of rainfall erosivity for soil degradation prevention, very few studies have addressed its spatial and temporal variability. In this study the time variation of rainfall erosivity in the Ebro Valley (NE Spain) is assessed for the period 1955–2006. The results show a general decrease in annual and seasonal rainfall erosivity, which is explained by a decrease of very intense rainfall events whilst the frequency of moderate and low events increased. This trend is related to prevailing positive conditions of the main atmospheric teleconnection indices affecting the West Mediterranean, i.e. the North Atlantic Oscillation (NAO), the Mediterranean Oscillation (MO) and the Western Mediterranean Oscillation (WeMO).
Highlights
Rainfall erosivity can be defined as the potential of a rainfall event to erode soil, and is a consequence of the interaction of several precipitation characteristics at the event scale
Rainfall erosivity models take into account the continuous and discrete characters of precipitation by considering precipitation amounts and intensities together with the energy released by raindrops when they hit the soil surface
Negative trends were found by other authors analyzing extreme precipitation on the Iberian Peninsula, contrasting with broader studies indicating positive trends in extreme precipitation at the global and regional (Mediterranean basin) scales
Summary
Rainfall erosivity can be defined as the potential of a rainfall event to erode soil, and is a consequence of the interaction of several precipitation characteristics at the event scale. Individual raindrop impacts are able to detach the soil aggregates and strike them up into the air as rain splash, preparing them for being transported by sheet wash or other processes and causing a diffusive displacement of particles down the slope if the topography is not perfectly flat. Rain splash is able to disrupt the soil aggregates, and the redistribution of soil particles blocks the soil pores, causing crusting and reduced infiltration. Infiltration, saturation and excessive overland flow may occur as a consequence of the amount and intensity of precipitation over short time periods, causing sheet and concentrated flow with high potential for detaching and transporting soil particles. It is expected that the annual precipitation will decrease in the Mediterranean, while higher amounts of erosive rainfall can be expected as a consequence of changes in precipitation variability and precipitation extremes
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