The effectiveness of loose rock check dams for gully control in Tigray, northern Ethiopia |
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Authors: | J. Nyssen M. Veyret-Picot J. Poesen J. Moeyersons Mitiku Haile J. Deckers G. Govers |
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Affiliation: | Laboratory for Experimental Geomorphology, KU Leuven, Redingenstraat 16, B–3000 Leuven, Belgium.;Department of Land Resources Management and Environmental Protection, Mekelle University, PO Box 231, Mekelle, Ethiopia.;Department of Agriculture and Forestry Economics, Royal Museum for Central Africa, B–3080 Tervuren, Belgium.;Institute for Land and Water Management, KU Leuven, Vital Decosterstraat 102, B–3000 Leuven, Belgium. |
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Abstract: | Abstract. Over the last two decades, large gully control programmes have been established in Ethiopia. Based on detailed observations and measurements of 400 check dams in the highlands near Hagere Selam (Tigray, northern Ethiopian Highlands), the effectiveness of the check dam technique was assessed. In this study, catchment area, slope gradient, technical characteristics and the presence of smectite clays are the main factors controlling dam stability. Simple and logistic regression techniques were used to analyse the data. The frequent collapse of dams (39% after two years) is strongly associated with drainage area ( A ) and slope gradient of the soil surface near the gully ( S ), the product of these factors ( S × A ) being a proxy for runoff energy. Good functioning dams have a spillway, apron, concave plan form (when looking downslope) and are built at vertical intervals and with heights that result in a negative slope gradient of the line connecting the spillway and the foot of the upstream dam. Therefore, a reverse slope of this line is recommended. Furthermore, if large cracks are present in smectite-rich soils, the construction of check dams can lead to piping and concentrated flow bypassing the dam. Given that the collapse of some check dams seems inevitable where catchment areas are large or there are steep slopes, it is necessary to repair dams as soon as partial collapse starts and to complement this gully control technique with biological control measures. |
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Keywords: | Check dam Ethiopia gully control gully erosion land degradation soil erosion topography |
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