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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #372062
Research Project: Managing Water and Sediment Movement in Agricultural Watersheds

Location: Watershed Physical Processes Research

Title: Arresting gully formation in the Ethiopian highlands

Author
item TEBEBU, TIGIST - Cornell University
item ZEGEYE, ASSEFA - Cornell University
item Langendoen, Eddy
item AYELE, GETANEH - Bahir Dar University
item TILAHUN, SEIFU - Bahir Dar University
item AYANA, ESSAYAS - Bahir Dar University
item STEENHUIS, TAMMO - Cornell University

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 7/5/2013
Publication Date: 11/1/2013
Citation: Tebebu, T.Y., Zegeye, A.D., Langendoen, E.J., Ayele, G., Tilahun, S.A., Ayana, E.K., Steenhuis, T.S. 2013. Arresting gully formation in the Ethiopian highlands. In Mekuria, W., editor. Rainwater Management for Resilient Livelihoods in Ethiopia. Nairobi, Kenia: ILRI. p. 196-203.

Interpretive Summary: Severe gully erosion is a major cause of land degradation in northern Ethiopia. Classic gully erosion control measures such as check dams have been unsuccessful in halting gully formation and growth in the humid northern Ethiopian highlands. Scientists at the USDA, ARS, National Sedimentation Laboratory in collaboration with researchers at Cornell University and Bahir Dar University, Ethiopia, are using the USDA, ARS computer models BSTEM and CONCEPTS for developing more effective gully rehabilitation measures for humid northern Ethiopia. These models were applied for preliminary investigations of the possibility to stabilize a rapidly expanding gully in the Debre-Mewi watershed, about 30 km south of Lake Tana through regrading. The models indicated that any gully rehabilitation project should first stabilize the head cuts. This can be achieved by regrading these head cuts to slope of 40 degrees and protecting the bare surface soils. Head cuts will otherwise move uphill in time and destroy any improvements.

Technical Abstract: Over the past five decades, gullying has been widespread and has become more severe in the Ethiopian highlands. Only in very few cases, rehabilitation of gullies has been successful in Ethiopia due to the high costs. The objective of this paper is to introduce cost effective measures to arrest gully formation. The research was conducted in the Debre-Mewi watershed located at 30 km south of Bahir Dar, Ethiopia. Gullying started in the 1980s following the clearance of indigenous vegetation and intensive agricultural cultivation, leading to an increase of surface and subsurface runoff from the hillside to the valley bottoms. Gully erosion rates were 10–20 times the measured upland soil losses. Water levels, measured with piezometers, showed that in the actively eroding sections, the water table was in general above the gully bottom and below it in the stabilized sections. In order to develop effective gully stabilizing measures, we tested and then applied the BSTEM and CONCEPTS models for their applicability for Ethiopian conditions where active gully formation has been occurring. We found that the model predicted the location of slips and slumps well with the observed groundwater depth and vegetation characteristics. The validated models indicated that any gully rehabilitation project should first stabilize the head cuts. This can be achieved by regrading these head cuts to slope of 40 degrees and armoring it with rock. Head cuts will otherwise move uphill in time and destroy any improvements. To stabilize side walls in areas with seeps, grass will be effective in shallow gullies, while deeper gullies require reshaping of the gullies walls, then planting the gully with grasses, eucalyptus or fruit trees that can be used for income generation. Only then there is an incentive for local farmers to maintain the structures.