Ephemeral gully erosion in a wheat-cultivated area in Sicily (Italy)

Ephemeral gully erosion is responsible for heavy damage to agricultural land and causes sedimentation and drainage network formation in most regions. Ephemeral gully length, width and depth were measured over a 5-yr period in an area of about 120 ha of heavy soils cultivated with durum wheat in Sicily (Italy) in order to quantify the soil losses and to examine, by statistical analysis, the relationships between this kind of erosion, precipitation and the characteristics of the watersheds. Ephemeral gully formation was observed for 4 yr out of five in the study area. A mean length of about 36 m ha(-1) yr(-1) and mean soil losses of 3.3 m(3) ha(-1) yr(-1) were measured. The channel depth reached a maximum value (>1 m) 3 yr out of four. In the examined soils, this kind of erosion occurs when the moisture content of the soil is high: regression analysis indicates that the soil moisture content can be expressed by the amount of precipitation for 3 days. In the observation period, the minimum 3-day rainfall which gave rise to channel formation was 51 mm; since the 51 mm return period is less than 2 yr, the risk of erosion is high. Mean depth and width, which are the channel characteristics that vary the least between the different years, seem to be controlled by the soil, crop and field characteristics, whereas the precipitation regime seems mainly to influence their number and length. Regression equations were performed to estimate ephemeral gully surface area and soil losses measuring the length alone. Length measurement by the global position system is sufficiently accurate and fast. The influence of watershed surface area and length on ephemeral gully erosion indicates that a reduction in field area and length may be an effective measure to reduce this kind of erosion. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.