Global Ecology and Conservation (Dec 2020)
Current extent, temporal trends, and rates of gully erosion in the Gumara watershed, Northwestern Ethiopia
Abstract
Gully erosion is among the foremost challenges for the sustainability of the land resource and agricultural activities in sub-humid northwestern Ethiopia. Understanding the situation of the current extent and temporal variation of gully expansion can help to curb the problem. However, temporal gully erosion studies are very limited. In this paper, the current extent, temporal change trends, and rates of gully erosion in the Gumara watershed are studied. A total of 241 cross-sections representing 44 gullies were surveyed, and their temporal changes over the period 2001–2018 are analyzed. The analysis was performed using a time series high-resolution satellite imageries and field surveys. The study result shows that currently, the total gully length is 10.04 km, and gully density is 1.87 km km−2. The total soil loss was 273, 066 t since the first gully incision in 1985. Similarly, the estimated total surface area damage was 11.42 ha. Gully length, density, surface area damage, and soil loss had increased from 3.83 to 10.04 km, 0.71–1.87 km km−2, 3.31–11.42 ha, and 60.58 to 273.07 × 103 t, respectively over the period 2001–2018. The average short-term rate of change of gully length, surface area damage, and soil loss were 1.75 m ha−1 yr−1, 13.44 m2 ha−1 yr−1, and 30.5 t ha−1 yr−1, respectively from 2001 to 2005. The medium-term average rate of increase in length, surface area damage, and soil loss was 0.68 m ha−1 yr−1, 8.91 m2 ha−1 yr−1, and 23.34 t ha−1 yr−1, respectively, over the period 2001–2018. Gullies are young and actively expanding. The expansion trend has been increasing with a decreasing rate, but the rate is still very high. However, gully rehabilitation practices so far are very limited, although, little effort is made in eucalyptus tree plantations by smallholder farmers. Therefore, the existing soil and water conservation practices on plots need to be strengthened, and large-scale gully bank rehabilitation is recommended by participating in all stakeholders’.
