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Spatial Characterization of Riparian Buffer Effects on Sediment Loads from Watershed Systems
Momm, H., R. Gingner, Y. Yuan, M. Locke, AND R. Wells. Spatial Characterization of Riparian Buffer Effects on Sediment Loads from Watershed Systems. JOURNAL OF ENVIRONMENTAL QUALITY. American Society of Agronomy, MADISON, WI, 43(5):1736-1753, (2014).
The AnnAGNPS buffer GIS technology has been developed 466 to serve as a template to determine the required information needed for existing models, empirical relationships and/or physically based models and can be used with new models/relationships for sediment trapping efficiency that may be developed.
Understanding all watershed systems and their interactions is a complex, but critical, undertaking when developing practices designed to reduce topsoil loss and chemical/nutrient transport from agricultural fields. The presence of riparian buffer vegetation in agricultural landscapes can modify the characteristics of overland flow between the origin in upland agricultural fields and downstream water bodies such as streams, ponds, and lakes; most often the presence of such vegetative cover reduces flow velocity, in turn promoting sediment deposition and nutrient filtering. Watershed simulation tools, such as the USDA-Annualized Agricultural Non-Point Source (AnnAGNPS) pollution model, contains the necessary components to account for efficacy of vegetation in reducing sediment and chemical loads; however, these tools typically require detailed information for each riparian buffer zone throughout the watershed describing the location, width, vegetation type, topography, and possible presence of concentrated flow paths through the riparian buffer zone. Research was conducted to develop GIS-based technology designed to spatially characterize riparian buffers and estimate buffer efficiency in reducing sediment loads in a semi-automated fashion at watershed scale. The methodology combines modeling technology at different scales, individual concentrated flow paths passing through the riparian zone and at watershed scales. At the concentrated flow path scale, vegetative filter strip models can be applied to estimate the sediment trapping efficiency for each individual flow path, which are aggregated based on the watershed subdivision and used in the determination of the overall impact of the riparian vegetation at the watershed scale. This GIS-based technology is combined with AnnAGNPS to demonstrate the effect of riparian vegetation on sediment loadings from sheet and rill and ephemeral gully sources. The AnnAGNPS riparian buffer component represents an important step in understanding and accounting for the effect of riparian vegetation, existing and/or managed, in reducing sediment loads at the watershed scale. Additionally, this component provides watershed conservation managers the necessary tools to characterize and evaluate existing and proposed implementation practices by providing the means to generate information describing the integrated effects of riparian 27 buffers, at multiple scales and, consequently, 28 offering information for targeted action to mitigate non-point source pollution resulting for a better utilization of watershed resources.