Origin and erosive consequences of high-intensity rainfalls in the Mediterranean region

Abstract

Erosive processes of soil by water have always showed serious problems, mainly in those areas such as the Mediterranean environment, where the vigour of the surface, frequently low resistence of materials, little vegetation cover or bare ground, hard rainfalls and deficient management of resources, have led to favourable conditions for soil degradation. In the Mediterranean area of Spain agricultural andforest soil erosion is one ofthe most serious environmental problems. The erosivity of Mediterranean rainfalls highly depends both on the intensity and on the volume of precipitations. Rainfalls in the Mediterranean area are characterized by their fortuitousness and their concentration in a few days, particularly in Autum. Rainfalls of 100, 200 and even 300 mm, registered by pluviometers in a few hours period, release hígh amounts of energy whose consequencies are visible everywhere: heavy soillosses, gullying, undermining, landsliding, piping, bulky sedimentations, flooding ... The evaluation of erosion rates generated by rainfalls, which constitutes the basisfor the determination offactor R of the U.S.L.E., presents some problems. However, the results of the erosive elficacy of heavy rainjaUs are evident all over the Mediterranean area.