Medium-term evolution of some ephemeral gullies in Sicily (Italy)

• The channel size of the ephemeral gullies deepened and enlarged.
• The ephemeral gully length decreased in the downstream area of the watersheds.
• Ephemeral gullies evolved towards permanent gullies.

In this study, the medium-term evolution of some erosion channels (ephemeral gullies, EGs) initiated in a wheat-cultivated area on silty-clay-loam soils in central Sicily (Italy) in 1995 was studied over 18 years. The studied EGs showed a cyclic behaviour. They appeared during the rainy season, were erased from July to October by soil infill from areas adjacent to the channel using ordinary tillage equipment, and, in most years, they reappeared in the same position during the following rainy season. Between 1995 and 2013, some field surveys were conducted to measure the channel dimensions (length, depth, width, surface area and volume). The channel size evolved over time. The depth and width increased from 76% to 90% in different EGs, reaching a depth greater than 1 m and an upper width greater than 2 m. These dimensions interfere with conventional tillage operations, and farmers suspend their efforts to fill in the channels. At the same time, the study showed that the EG length increased until almost 2006 and decreased in more recent years due to natural infilling beginning in the downstream area of the watersheds where the gradient is less. The average infilling rate ranged from 1.1 to 4.3 m year−1. The results, on the whole, show how, once formed, EGs evolve towards permanent channels (gullies) and then can be naturally filled if the soil management system and precipitation regime are invariant.