Analysing the factors affecting gully development and their relationships with land-use changes in the east Alentejo (Portugal)

Abstract

The land abandonment and land-use changes as a consequence of the implementation of the European Union Common Agricultural Policy (C.A.P.), in the SE of Portugal, have been generating, differences in the equilibrium of the geomorphic processes. The head waters catchments of some of the Guadiana River tributaries show in the study area several degrees of gully initiation and development both on the hillsides and valley bottom infill. This gully generation process is closely related with the changes in the soil and cover properties occurring when agricultural practises have been replaced by intensive grazing areas or by abandoned land. High resolution panchromatic and Landsat images, dating from the last 40 years have been analysed in combination with field observations and the analysis of the data from soil erosion plots series in the Estação Experimental de Vale Formoso, in order to establish and parameterise the sequence of changes in soil surface properties and vegetation cover and distribution. The results show the connection between the different degrees of gully development and their morphological characteristics with the land cover properties at different times and after different sequences of land-use changes