Evaluation of erosion control geotextiles on steep slopes. Part 1: Effects on runoff and soil loss

Geotextiles have been demonstrated to be effective in reducing erosion and subsequent slope degradation processes. However, most studies devoted to assessing the effectiveness of those elements have considered small or intermediate slope gradients (normally ≤30°), whereas real engineering works often lead to steeper slopes needing protection. In addition, although a large amount of laboratory studies exist on this topic, there are few articles reporting field experiments which consider large plots, real precipitation and prolonged study periods. This paper is the first of two in which the performance of erosion control geotextiles on steep slopes (45° and 60°) has been assessed. In this paper, the influence of geotextiles on runoff and soil loss reduction was evaluated. The second paper focuses on the effects of geotextiles on the establishment and growth of vegetation on the slope. The research was carried out on an experimental embankment built in Pamplona (Spain) following standard construction procedures in order to resemble real engineering slopes. Two biological geotextiles (jute net and coir blanket) and a synthetic polyester geogrid, installed in two positions (surface-laid and buried), were evaluated and compared with a vegetated hydroseeded control plot. After each significant rain event, runoff and soil loss amounts produced on each plot were recorded. The results showed that coir and jute geotextiles produced 2–3 times larger runoff volumes than the control plots on both the 45° and 60° slopes, whereas the synthetic geogrid did not give significantly different runoff rates from the control (at p