Effectiveness of palm and bamboo geotextiles in reducing concentrated flow erosion

Rills and gullies, caused by concentrated flow erosion, represent an important sediment source in many environments (Poesen et al., 2003). Studies indicate that vegetation can be very effective in controlling gully development. However, the establishment of a vegetation cover can be delayed or obstructed by the development of rills and gullies due to concentrated flow erosion. Before the vegetation has reached a critical cover and root density to significantly reduce concentrated flow erosion, a period of high erosion risk occurs. Hann and Morgan (2006) indicate that applying geotextiles on the soil surface is the most efficient method to control erosion until a critical vegetation cover has been established. Preliminary investigations suggest palm-mat geotextiles could be an effective and cheap soil conservation method, with enormous global potential. However, very little is known about the effectiveness of (palm) geotextiles in reducing concentrated flow erosion. Almost no data are available on the impacts of palm geotextiles on the hydraulic, hydrologic and erosion characteristics of concentrated flow for a range of environmental conditions. Therefore, the objectives of this study are (i) to assess the effectiveness of two palm-mat and one bamboo geotextile in increasing the hydraulic roughness of the soil surface under concentrated overland flow and in reducing soil erosion rates by concentrated flow on an erodible soil type and for a range of flow shear stresses; and (ii) to investigate which is the most appropriate hydraulic variable (e.g. shear stress, unit length shear force or stream power) to predict the net soil detachment by concentrated flow.