Earth surface processes and landforms vol:33 issue:5 pages:695-711
This paper analyses the factors that control rates and extent of soil erosion processes in the
199 ha May Zegzeg catchment near Hagere Selam in the Tigray Highlands (Northern Ethiopia).
This catchment, characterized by high elevations (2100–2650 m a.s.l.) and a subhorizontal
structural relief, is typical for the Northern Ethiopian Highlands. Soil loss rates due to
various erosion processes, as well as sediment yield rates and rates of sediment deposition
within the catchment (essentially induced by recent soil conservation activities), were measured
using a range of geomorphological methods. The area-weighted average rate of soil
erosion by water in the catchment, measured over four years (1998–2001), is 14·8 t ha−1 y−1,
which accounts for 98% of the change in potential energy of the landscape. Considering
these soil loss rates by water, 28% is due to gully erosion. Other geomorphic processes, such
as tillage erosion and rock fragment displacement by gravity and livestock trampling, are
also important, either within certain land units, or for their impact on agricultural productivity.
Estimated mean sediment deposition rate within the catchment equals 9·2 t ha−1 y−1.
Calculated sediment yield (5·6 t ha−1 y−1) is similar to sediment yield measured in nearby
catchments. Seventy-four percent of total soil loss by sheet and rill erosion is trapped in
exclosures and behind stone bunds. The anthropogenic factor is dominant in controlling
present-day erosion processes in the Northern Ethiopian Highlands. Human activities have
led to an overall increase in erosion process intensities, but, through targeted interventions,
rural society is now well on the way to control and reverse the degradation processes, as can
be demonstrated through the sediment budget.