Impact of <i>Miscanthus giganteus</i> and short-rotation coppice vegetative barriers on surface runoff velocity

Accelerated erosion can have detrimental effects on the chemical, physical, and biological quality of soils and surface water bodies. It impacts agricultural productivity and soil ecosystem services. Vegetative barriers can help address this challenge by regulating flows within agricultural watersheds, reducing runoff velocity, and trapping eroded sediments. However, only a limited number of documented studies have quantified the effectiveness of Miscanthus giganteus and short rotation coppice (SRC) against surface runoff. Therefore, this study specifically aims to investigate the effectiveness of these two vegetative barriers in reducing surface runoff and facilitating infiltration. A series of runoff simulation experiments were conducted on silt loam soils in Wallonia (Belgium) between 2021 and 2024, focusing on Miscanthus giganteus and SRC willow strips with varying planting densities and ages (2 to 12 years) on slopes ranging from 4 to 12%. This allowed to determine the hydraulic roughness based on the water depth in the vegetation strip. The runoff simulation results reveal a Manning coefficient (n) ranging between 0.37 and 0.8 s.m-1/3 for Miscanthus giganteus and between 0.32 and 0.59 s.m-1/3 for SRC depending on different factors (slope, plant density, flow rate and age of plantation). These findings suggest that vegetation strips, particularly Miscanthus giganteus, may be more effective than conventionally used grass strips in slowing down surface flows. Moreover, measurements using the water balances of the runoff tests indicate an infiltration rate of 130±30 mm/h for SRC and 83±20 mm/h for Miscanthus giganteus, showcasing the ability of both barriers to absorb upland runoff. Overall, these results underscore the potential of Miscanthus giganteus and SRC willow strips to improve hydrological functioning of agricultural catchments