Abstract
The purpose of this paper was to evaluate technical conformity of bench terraces in the Eastern Province of Rwanda. A sample of 180 actual bench terraces from 12 sites located in this Province was tested against technical standards and models provided for by the Ministry of Agriculture of Rwanda and Food and Agriculture Organization of the United Nations. The results showed that many sites have been constructed with no consideration of these technical guidelines. Terraces were built on land slopes lower or higher than standards while terrace riser slopes above 90% and height above 2.9 m were frequent. Findings indicated weak correlation coefficient (r=0.314), although very significant, between field-measured and Agriculture Organization model-computed vertical intervals, and very weak but significant correlation coefficient (r = 0.194) between terrace measured and model-derived widths. In such circumstances, land terracing might have increased risks of landslide and erosion with no sustainable benefit for soil erosion control and crop production. Key words: Bench terraces, soil erosion, technical efficacy, Eastern province.  
Highlights
More than 80% of the world’s agricultural land suffer moderate to severe soil erosion
Land slope determination is the imperative criteria in selecting soil conservation and management practices for soil erosion control
The parameters include vertical interval measured on field (VIF), vertical interval calculated using the FAO formula (VIFAO), width measured on field (WBF), and width calculated using FAO formula (WBFAO)
Summary
More than 80% of the world’s agricultural land suffer moderate to severe soil erosion. The mean annual soil erosion loss on cropland has been estimated at about 30 Mg/ha, while reported values vary from 0.5 to over 400 Mg/ha per year (Pimentel and Kounang, 1998). Recent soil erosion loss estimates from the intensively cultivated highlands of the upper Akagera River indicated average amounts of 35.1 tons/ha in southern Rwanda and 19.2 tons ha-1 in northern Burundi (Karemangingo et al, 2014). The history of bench terraces in Rwanda is linked to policies and regulations by the Government and to interventions by Non-Government Organizations (NGOs) (Bizoza and de Graff, 2012). In order to maintain the top soils, which are rich in nutrients, and to keep the riser of the terrace intact, a bench terrace is constructed by breaking up the 25 to 55% slope gradient into several shorter and levelled segments (Posthumus, 2010)
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