Effects of land-use changes in vegetation cover and sidewall erosion in a gully head of the Penedès region (northeast Spain)



The present research addresses the effects of land-use changes in the evolution of vegetation cover on gully erosion in the Penedès region of northeast Spain. The contribution of vegetation cover to gully wall stabilization is also discussed. The catchment area of the gully is 60·2 ha and is mainly composed of vineyards. In this area, large gullies have developed on Tertiary marls and unconsolidated sandstones. Detailed aerial photographs (1 : 5000 and 1 : 7000 scale) of three dates (1975, 1995 and 2002) were ortho-rectified to derive land-use information in the catchment, gully vegetation cover and height information to construct detailed digital elevation models. Land-use and gully vegetation cover mapping of the most recent period was assisted by means of fieldwork and a photo-interpretation key constructed to help map the older dates. Soil loss in the catchment was estimated for the 1975 and 2002 scenarios to determine the relations between land-use changes to vegetation cover changes and gully sidewall erosion. The Revised Universal Soil Loss Equation was applied for that purpose. Sidewall mass movements were determined by subtraction of digital elevation models (1 m resolution) of each period. The results show important land-use changes in the catchment due to field reorganization for the plantation of mechanized vineyards. It increased soil loss from agricultural fields by 26·5%, which influenced vegetation cover dynamics on gully walls, with an important development of scrubland to forest, and gully erosion, with sidewall retreat at rates of 0·025 to 0·50 ha y−1 and mass movements at rates of 16 to 63·2 Mg ha−1 y−1. These results indicate that vegetation cover on gully walls, although suggesting an improvement with respect to wall protection against splash, sheet and rill erosion, did not affect sidewall retreat and mass movements. Copyright © 2009 John Wiley & Sons, Ltd.