Publications

Frankl, A.,  Poesen, J.,  Moeyersons, J. & Nyssen, J. 2015. ‘10 Gully Development in the Tigray Highlands’. In: Billi, P. (ed), Landscapes and Landforms of Ethiopia. Series ‘World Geomorphological Landscapes’. Dordrecht : Springer, pp. 191-200. (PR) DOI: DOI 10.1007/978-94-017-8026-1_10.

Chapter in an edited book / Article in an edited book

In the Tigray highlands, gully development is linked to poverty-driven unsustainable use of the land in a vulnerable semi-arid and mountainous environment, where intense rainfalls challenge the physical integrity of the landscape. Over the last two centuries, three major phases in the hydrological regime of the region could be distinguished. In the first phase, between 1868 (or earlier) and ca. 1965, the relatively stable gully channels showed an oversized morphology inherited from a previous period when external forcing of environmental conditions caused significant channel development. In the second phase (ca. 1965–ca. 2000), increased aridity and a continued vegetation clearance accelerated dynamics of the gully system. A sharp increase in gully headcut retreat rates, network densities and volumes could be quantified for that period. With the widespread implementation of soil and water conservation measures, erosion rates decreased, which announced the start of the third hydrogeomorphic phase since ca. 2000. In 2010, about one-fourth of the gully channels were stabilized. These hydrogeomorphic developments correspond to a gully cut-and-fill cycle in the second half of the twentieth century and suggest that a pre-1868 cut cycle took place.