Similarity between morphological characteristics of rills and ephemeral gullies in Sicily, South Italy

This paper reports the results of a field investigation aimed to establish morphological similarity between rills and ephemeral gullies. Rill measurements were made on 14 plots having a surface area of 22–352 m2 located on a 14% slope and on a plot 6 m wide and 22 m long having a uniform 22% slope. The plots are located on the experimental station for soil erosion measurements, ‘Sparacia’, of the Agricultural Faculty of Palermo University, in Sicily, Italy. All plots are subjected to natural rainfall. The measurements were made immediately following five events between November 2004 and December 2005. The ephemeral gully measurements were made on a cultivated area of about 120 ha, located in Central Sicily, which is representative of many soil-crop conditions in the Mediterranean basin. The morphological similarity between rill and ephemeral gully was first tested. Then a power relationship between rill or gully volume and length, theoretically deduced by dimensional analysis and self-similarity theory, was applied. This power relationship needs a different scale factor for rill and gully measurements. Finally, using two dimensionless groups representative of the channel morphology variables, the analysis showed that a single relationship can be applied to rill and gully measurements.