GIS-based soil erosion modelling under various steep-slope vineyard practices

Soil erosion can cause a progressive degradation of hillslopes, especially in steep-slope agricultural landscapes. In this study, the formation of spatial erosion patterns was evaluated in three typical steep-slope vineyard cultivation practices in northern Italy: dry-stone wall terraces, earth bank terraces and vertical cultivation (Italian: rittochino). UAV surveys in three vineyards provided high-resolution data on topography and land use serving as input for two GIS-based erosion models: the Revised Universal Soil Loss Equation (RUSLE) and SIMulated Water Erosion model (SIMWE). Annual RUSLE simulations showed how the two terracing practices (i.e. dry-stone walls and earth banks) effectively safeguarded large areas from soil loss, whereas the non-terraced vertical cultivation produced widely distributed soil loss with increasing severity according to slope length and steepness. In intense single-event conditions simulated by SIMWE, all three practices showed the formation of critical preferential surface flow patterns, corresponding to several field-observed erosion patterns (piping of stone walls, landslides on earth banks, and rill erosion in the non-terraced vineyard), while also in this case showing the highest erosion rates for the non-terraced vertical cultivation. Simulated flow concentration was strongly determined by the spatial organisation of the hillslope, roads and vines, and several strategies were discussed for erosion mitigation (including drainage systems or enhanced soil cover). Furthermore, the results indicated that SIMWE is an optimal approach for the recognition of soil erosion processes occurring during intense rainfall conditions. This study provides an example of high-resolution erosion risk evaluation, which should play a crucial role in the design and management of steep-slope vineyards.