Monitoring Rainfall Erosivity in the Sparacia Experimental Area by an Optical Disdrometer

The kinetic power of rainfall plays a fundamental role in soil erosion processes. Kinetic power can be determined by knowing both drop size distribution (DSD) and drop falling velocity. This paper reports the results obtained by the DSDs detected by an optical disdrometer installed in two Sicilian sites. In particular, the disdrometer was installed at Palermo in the period June 2006 – May 2014 and at Sparacia experimental station in the period March 2017 – December 2019. The DSDs, that are detected using a sampling time equal to 1 min, after aggregation by rainfall intensity classes, are presented highlighting the differences on DSDs characteristics for the two experimental sites. The rainfall kinetic power was calculated by combining DSDs and the falling velocity obtained by the relationship suggested by Ferro (Ferro, V.: Tecniche di misura e monitoraggio dei processi erosivi. Quaderni di Idronomia Montana (21/2), 63–128 (2001).). The reliability of the empirical relationships estimating kinetic power by only rainfall intensity proposed by Wischmeier and Smith (Wischmeier, W.H., Smith, D.D.: Predicting Rainfall Erosion Losses-A guide to conservation planning. Agriculture Handbook: United States Department of Agricolture, Washingtin, DC; 537 (1978).) and Brown and Foster (Brown, L.C., Foster, G.R.: Storm erosivity using idealized intensity distribution. Trans. ASAE 30, 379–386 (1987). https://doi.org/10.13031/2013.31957 ), is firstly verified. Furthermore, the relationship theoretically deduced by Carollo et al. (Carollo, F.G., Ferro, V., Serio, M.A.: Reliability of rainfall kinetic power- intensity relationships. Hydrol. Process 31, 1293–1300 (2016). https://doi.org/10.1002/hyp.11099 ), which allows to estimate the kinetic power by rainfall intensity and a characteristic diameter (median volume diameter), is tested. Finally, the comparison between the relation kinetic power – intensity detected in the two sites is presented.