MODELLING THE PROBABILITY OF GULLY DEVELOPMENT IN VINEYARD PARCELS FACTORS

A. Meyer & J.A. Martinez-Casasnovas
Department of Environment & Soil Science
University of Lleida (Spain)




An important extension of the NE Spain Mediterranean area has a high risk of gully erosion due to rainfall and lithological characteristics. In some regions, as the Alt Penedes-Anoia (Catalonia), specific land uses as vineyards contribute to increase the risk. This study presents a method to model the risk of gully development in vineyard parcels. The risk is evaluated in terms of the probability that ephemeral gullies develop in a parcel, depending on terrain and cropping system variables. A total of 40 parcels (20 with gully erosion and 20 without) were studied and sampled according to a list of 33 variables (relief, soil, cropping system and management practices characteristics). To identify the factors explaining the existence of gully erosion (considering correlation between factors), a stepwise selection was performed. The selected factors, slope degree and slope form in this case study, were considered as variables in a logistic regression of binary response. This produced an equation that computes the probability of gully development with a Good-of-Fit value of 0.842. The method was implemented in a raster based GIS, and the terrain variables for the application of the model were obtained from a 25 m resolution DEM. The validation of the model in other 52 parcels yielded an overall accuracy of 84.6%. The risk of gully erosion increases with the slope degree in an exponential way and from convex to concave contour form.