Soil erosion by concentrated flow can cause serious environmental damage. Erosion-control geotextiles have considerable potential for reducing concentrated flow erosion. However, limited data are available on the erosion-reducing potential of geotextiles. In this study, the effectiveness of three biological geotextiles in reducing soil losses during concentrated flow is investigated. Hereto, runoff was simulated in a concentrated flow flume, filled with an erodible sandy loam on three slope gradients (13·5, 27·0 and 41·5%). Treatments included three biological geotextiles (borassus, buriti and bamboo) and one bare soil surface. Darcy–Weisbach friction coefficients ranged from 0·01 to 2·84. The highest values are observed for borassus covered soil surfaces, followed by buriti, bamboo and bare soil, respectively. The friction coefficients are linearly correlated with geotextile thickness. For the specific experimental conditions of this study, borassus geotextiles reduced soil detachment rate on average to 56%, buriti geotextiles to 59% and bamboo geotextiles to 66% of the soil detachment rate for bare soil surfaces. Total flow shear stress was the hydraulic parameter best predicting soil detachment rate for bare and geotextile covered surfaces (R² = 0·75–0·84, p < 0·001, n = 12–15). The highest resistance against soil detachment was observed for the borassus covered soil surfaces, followed by buriti, bamboo and bare soil surfaces, respectively. Overall, biological geotextiles are less effective in controlling concentrated flow erosion compared with interrill erosion. Copyright © 2009 John Wiley & Sons, Ltd.

Despite palm-leaf geotextile mats having the potential to advance soil conservation technologies, field studies using geotextiles as complete cover and buffer strips in reducing rates of soil erosion by water are limited. Hence, the utilization of these mats as a potential soil conservation technique is investigated at Hilton, east Shropshire, UK (52°33′5.7″N, 2°19′18.3″W). Geotextile mats constructed from Borassus aethiopum (Borassus palm of West Africa) and Mauritia flexuosa (Buriti palm of South America) leaves are termed Borassus mats and Buriti mats, respectively. Field experiments have been conducted at Hilton since January 2007, to study the effects of emplacing Borassus and Buriti mats on the erosion of a loamy sand soil. Two sets (12 plots each) of experiments were established to study the effects of Borassus and Buriti mats on splash height and splash erosion. In both sets, 6 randomly-selected plots were completely covered with mats, and the rest were bare. Ten runoff plots (10 × 1 m on a 15° slope) were also established, with duplicate treatments to study the effectiveness of these mats for soil and water conservation. The treatments were: (i) bare soil; (ii) permanent grassed; (iii) bare soil with 1 m Borassus mat buffer zones at the lower end of the plots; (iv) bare soil with 1 m Buriti mat buffer zones at the lower end of the plots and (v) completely covered with Borassus mats. Results (during 22/01/07–21/01/08; total precipitation = 919.0 mm; n = 22 sets of measurements) indicate that Borassus mat-cover on bare soil significantly (P < 0.05) reduced total soil splash erosion by 90% compared with bare plots (24.81 kg m−2). Plots with Borassus mats had 51% less mean splash height than bare plots (n = 21 sets of measurements). However, Buriti mat-cover on bare soils had no significant (P < 0.05) effect on soil splash height or splash erosion. Results of runoff plots (08/01/07–14/01/08; total precipitation = 923.4 mm; n = 29 sets of measurements) showed permanent grass plots had the smallest runoff coefficient and the largest sediment yield reduction effectiveness (SYRE). Total runoff from the Borassus buffer zone plots (4.1 L m−2) was 83% less than the bare plots and total sediment yield was 93% less than the bare plots (2.32 kg m−2). Although, Borassus buffer zone plots had similar effects in reducing soil loss to Borassus completely-covered plots, the later treatment yielded 50% more runoff. Borassus buffer strip plots had less SYRE than the Buriti buffer zone plots. Mass per unit area and thickness of both geotextiles decreased after 3 months of surface application. However, moisture sorption depth and cover percentage of both geotextiles increased. Hence, it is recommended to cover palm-mat geotextiles as buffer strips for soil and water conservation on erodible moderate slopes.