Evaluation of biological geotextiles for reduction of runoff and soil loss

Abstract

The objective of the work reported is to evaluate the effectiveness of selected types of biological geotextile in reducing runoff and soil lossin continental, temperate and tropical environments. Laboratory simulations used various rainfall intensities, flow shear stresses and slope gradient and field plot data were collected from seven countries. The laboratory experiments indicate that all tested biological geotextiles are effective in reducing interrill runoff (32-73% of the value for bare soil) and interrill erosion rates (5-27 % of the value for bare soil). Since simulated concentrated flow discharge sometimes flows below the geotextiles, their effectiveness in reducing concentrated flow erosion is significantly less (25-153% of the value for bare soil). On field plots, where both interrill and rill erosion occur, all tested geotextiles reduced runoff depth on average to 17-63 % of the control value for bare soil and in some cases, runoff depth increased compared to bare soil surfaces, which can be attributed to the impermeable and hydrophobic characteristics of some biological geotextiles. In the field, soil loss rates due to interrill and rill erosion were reduced on average to 5-20 % of the value of bare soil by the biological geotextiles. For all environmental conditions, the relative reduction of both runoff and soil loss by geotextiles compared to bare soil, increased with increasing rainfall depth. Runoff depths are significantly more reduced by Buriti and Rice straw geotextiles on the longer field plots (6-10 m) compared to the short interrill laboratory plots (0.9 m). Only the Rice straw geotextiles are significantly more effective in reducing soil loss on the longer field plots compared to the short interrill laboratory plot.