Effects of land use and landscape on spatial distribution and morphological features of gullies in an agropastoral area in Sardinia (Italy)

According to the United Nations Convention to Combat Desertification (UNCCD), soil erosion is one of the main causes of desertification in the Northern Mediterranean. Recently, the role of channelled erosion in sediment delivery has been underlined by several studies. The aim of this paper is to describe a simplified experimental methodology settled up for studying the relationships between gully erosion and land use. The experimental site, which is wide about 720 ha, is located in a hilly area threatened by desertification in Central Eastern Sardinia (Italy). This area is characterised by irregular morphology with steep slopes, where agropastoral activities, particularly tillage with heavy machinery and overgrazing, are causing severe soil erosion and compromising agricultural productivity. Previous studies carried out in the same area highlighted the need to quantify and monitor soil erosion in order to outline management guidelines for farmers. In this study, an integrated methodology that uses aerial photographs and field surveys was applied to inventory the gullies of the area. The degree of activity and morphological characteristics of gullies were assessed in the field by measuring the position and shape of gully heads, and their width and depth. Total gully volume was also estimated. Relationships among distribution, density and morphological characteristics of gullies, and geomorphological features, land use and land use historical dynamics of the area have been studied. The results show the very significant impact of agricultural activities on gully activity and density.