Hydrological and erosive processes of an extreme stormy event in an almond tree steppe setting in the Iberian Peninsula southeast

Abstract

This research offers a quantitative study of the hydrological and erosive effects of an extreme stormy event (62mm in one hour) in Barranco de la Casa de la Parra basin, an almond tree steppe. The drainage basin and the synoptic situation are characterized.  For hydrological quantification, the rational method has been used according to Standard 5.2-IC of the Ministry of Development (Government of Spain), for a return period of 25 years. The erosive dynamics have been quantified through field measurements of a large gully originated by hydrological processes. The results consist of the measurement of hydrological variables that characterize the flash flood, as well as the estimate consequent loss of soil, both in volume and weight. We highlight a peak flow rate of 18m³/s able to excavate 1741m³ of materials. The results are interpreted as being a consequence of the type of soil (sedimentary basin) and the current main land use (almond trees), which unprotects the soil more and longer than the traditional uses (scrubland and a larger surface of cereals). It concludes by drawing attention to the apparent low sensitivity of the agrarian sector towards extreme erosion processes, which seem to be, in accordance with these results and with scientific literature, those that most intensely reconfigure the landscape in a scenario of agro-natural imbalance.