1a.Objectives (from AD-416)
Plan laboratory, field, and modeling studies to quantify erosion processes by concentrated flows in small agricultural areas with the final goal of improving erosion control practices.
1b.Approach (from AD-416)
Evaluate runoff and landscape properties such as topographic and soil profiles, and vegetative cover in field areas susceptible for ephemeral and edge-of-field gully erosion development. Complement field monitoring with laboratory measurements to characterize and quantify headcut migration, gully growth, and sediment yield from the selected areas. Description of water and sediment fluxes and sediment transport processes using models will allow the interpretation of the experimental results and their extrapolation to different conditions. Modeling efforts will cover a range of scales using analytical, BGK lattice schemes, and enhancements to the AnnAGNPS model.
Monitoring activities were performed through quarterly conference calls or email communications with the cooperators. Concentration flow erosion has been shown to be a significant contributor to total soil loss in Spain and U.S. landscapes. Erosion studies within an olive crop microcatchment of 6.1 hectares in Spain were performed with gullies identified using aerial ortophotography. The results of the application of the USDA AnnAGNPS model on this microcatchment, with enhanced ephemeral gully components, provides an examination of the contribution of ephemeral gullies to total soil loss, producing values between 26% and 56% of total annual sediment discharges. The acquisition of sediment data and the simulation of gully erosion processes at the microcatchment scale should be considered when applying hydrological applications on landscapes with ephemeral gully erosion in order to reflect the impact of conservation practices on controlling erosion. The use of natural cover and no-tillage conservation practices did not provide acceptable levels of protection from ephemeral gully erosion according to the results of the model. Additional conservation practices such as the use of stiff grass hedges close to the gullies especially in autumn are suggested in the catchment.