Land-use changes and their impacts on soil degradation and surface runoff of two catchments of Northern Ethiopia

Abstract

Land-use/land-cover changes and their associated impact on environment in the period from 1964 to 2006 was studied in two catchments located in the highland of Tigray using geographic information system and remote-sensing approaches supplemented with field measurements. Results show that, for all periods, cultivated land constitutes the most prevalent (>60%) land-use type and shows a total increase of 1.7 ha y−1 at Gum Selassa and a decrease of 5.5 ha y−1 at Maileba. Forest and woodland suffered more damage in both areas losing 32.8 ha (100%) and 53 ha (100%), respectively at Gum Selassa; and 1.74 ha (96.7%) and 52.7 ha (100%) at Maileba over four decades. At Gum Selassa, shrubland decreased by 1.26 ha y−1 while at Maileba it showed a slight positive increment of 0.38 ha y−1. Area under settlement increased by a greater magnitude at Maileba (6.3 ha y−1) and a slight increase at Gum Selassa (1.4 ha y−1) in response to the rapid population increase. These changes in land uses/cover brought significant deleterious impacts on land degradation and surface runoff. The cumulative degradation index (DI) was negative for all land uses, with a higher value under Eucalyptus plantation (DI=−282) followed by cultivated land (DI=−260) at Maileba. Changes in land use/cover also decreased the water-storage capacity of soils by 1.63 and 1.09 mm y−1 at Gum Selassa and Maileba, respectively, with a corresponding increase in surface runoff by 2.7 and 2.3 mm y−1. Generally, the observed changes in land degradation and surface runoff are highly linked to the change in land use/land cover.