Hillslope runoff and erosion as affected by rolled erosion control systems: a field study

A replicated field study using rainfall simulation and overland flow application was conducted in central Oahu, Hawaii, on a clay-dominated Oxisol with a 9% slope. Three main treatment groups were examined: a bare treatment, a group of four rolled erosion control systems (RECSs) with open weave designs, and a group of five randomly oriented fibre RECSs. A total of 1122 measurements of runoff and erosion were made to examine treatment differences and to explore temporal patterns in runoff and sediment flux. All erosion control systems significantly delayed the time required to generate plot runoff under both simulated rainfall (35 nun h(-1)) and the more intense trickle flow application (114 nun h(-1)). Once runoff was generated during the rainfall application phase, the bare treatment runoff coefficients were significantly lower than those from the two groups of RECSs, as surface seal disruption by rilling is inferred to have enhanced infiltration in the bare treatments. During the more intense phase of overland flow application, the reverse pattern was observed. Interrill contributing-area roughness was reduced on the bare treatment, facilitating increased runoff to well-developed rill networks. Meanwhile, the form roughness associated with the RECSs delayed interrill flow to the poorly organized rills that formed under some of the RECSs. Regardless of runoff variations between treatments, sediment output was significantly lower from all surfaces covered by RECSs. The median cumulative sediment output from the bare surfaces was 6.9 kg, compared with 1.2 kg from the open-weave RECSs and 0.2 kg from the random-fibre RECSs. The random-fibre systems were particularly effective under the more stressful overland flow application phase, with 63 times less sediment eroded than the bare treatments and 12 times less than that from the open-weave systems. Architectural design differences between the two groups of RECSs are discussed in light of their relation to erosion process dynamics and shear stress partitioning. Copyright (C) 2006 John Wiley & Sons, Ltd.