The effectiveness of loose rock check dams for gully control in Tigray, northern Ethiopia

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.

How soil conservation affects the catchment sediment budget – a comprehensive study in the north Ethiopian highlands

“…Impact of integrated catchment management on sediment budget Positive effects of individual SWC measures on soil loss have been reported in various studies (see for instance, for Ethiopia: Bosshart, 1998;Descheemaeker et al, 2006c;Desta et al, 2005;Feleke, 1987;Mitiku et al, 2006;Nigussie et al, 2005;Nyssen et al, 2000aNyssen et al, , 2004bNyssen et al, , 2006bNyssen et al, , 2007Vancampenhout et al, 2006). This study aimed to assess the impact of integrated management on the sediment budget.…”

“…Besides these specific field measurement campaigns, many observations were made during related research in the catchment (Descheemaeker et al, 2006c;Desta et al, 2005;Nyssen et al, 2000aNyssen et al, , 2000bNyssen et al, , 2001Nyssen et al, , 2002Nyssen et al, , 2003bNyssen et al, , 2004bNyssen et al, , 2005Nyssen et al, , 2006aNyssen et al, , 2006bNyssen et al, , 2008bNyssen et al, , 2009cNyssen et al, , 2009dVancampenhout et al, 2006).…”

“…Check dams reduce the effective slope of the channel, thereby reducing the velocity of flowing water, allowing sediment to settle and reducing channel erosion. The control effects of check dams on runoff and peak discharges lead to a stabilization of the gully system (Nyssen et al, 2004b).…”

Multi‐temporal scale changes of streamflow and sediment load in a loess hilly watershed of China

“…Gully prevention and control measures include the establishment of grassed waterways and check dams with drop structures, and no tillage, topsoil compaction, doubling drilling and the establishment of grass and shrub hedges were also typically used (Poesen et al ., ). These gully erosion control measures, which led to sediment deposition and vegetation reestablishment, create new hydraulic conditions to control runoff and sediment evacuation (Nyssen et al ., ). There were 43 key projects for gully control in the watershed up to 1996.…”

Land Degradation in the Ethiopian Highlands

“…The efficiency of particular techniques cannot be discussed in depth here; the reader is referred to specialised publications (Herweg and Ludi 1999;SCRP 2000;Nyssen et al 2004cNyssen et al , 2007aNyssen et al , 2009aNyssen et al , 2010Gebremichael et al 2005;Haregeweyn et al 2006;Vancampenhout et al 2006;Wondumagegnehu et al 2007;Alemayehu et al 2009;Reubens et al 2009;Gebreegziabher et al 2009;Araya et al 2011;Lanckriet et al 2012;Muys et al 2014;Gebreyohannes et al 2014). …”